Any species returning to the land twice throughout their evolution?

Any species returning to the land twice throughout their evolution?

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Here's a question from my son I've found interesting enough to ask here. There are plenty examples of species returning back to the water environment, like dolphins, sea lions, walruses, some snakes, crocodiles etc.

The question is - are there any evidences that in evolution of certain species there was return to the land twice, that is, they've came from sea, then evolve as land species, then, again, evolved to somewhat marine or fresh-water and, finally, turn into land species again?

UPD Chordate are the most interesting but any example, even plants, would be nice.


Life emerged in the water. Ancestors of insects, spiders, myriapods and crustaceans were probably terrestrial (please correct me if that is wrong) but then, crustaceans evolved to living in the water again. Finally, woodlice went back onto land!

Hot topic: The evolution of thermal tolerance

Global warming is reshaping species distributions and altering ecological communities. Yet, we do not know what mechanisms have driven or obstructed past adaptation to temperature changes over evolutionary time scales. To answer this question, we performed a series of comparative analysis using the largest database of experimentally derived thermal tolerance limits GlobTherm. Concerningly, our research indicates that species have a limited ability to respond to rapid warming under climate change.

Example of physiological experiment measuring thermal tolerance limits in brittle stars at the Smithsonian Tropical Research Institute in Bocas del Toro Panama (Photo Credit. Piero Calosi).

What determines the geographic distribution of species across the Earth is an enduring and fundamental question in ecology. More than two centuries ago Alexander von Humboldt explored how climate affected species distributions. Global warming has added urgency to this endeavour as understanding how species tolerances to temperature relates to their distribution is crucial if we are to project climate change effects on biodiversity. Nevertheless, how thermal tolerance varies across the tree of life and the causes of the variation remain unknown.

Sweep working group supported by sDiv of the German Centre of integrative Biodiversity Leipzig. Participants standing left to right Laura Rodríguez, Alexander Singer, Ignacio Morales Castilla, Piero Calosi, Miguel Ángel Olalla-Tárraga, Ingolf Kühn, Carsten Rahbek, Joanne Bennett, Fabricio Villalobos and sitting left to right Bradford Hawkins, Brezo Martínez Adam Algar, Susana Clusella-Trullas, Jennifer Sunday, Sally Keith (Photo Credit. sDiv).

Like many researchers before me I was motivated to answer this question. So, after finishing my PhD in Australia, I move to Germany to take a post-doc in the synthesis centre of the German Centre of Integrative Biodiversity in Leipzig as part of the sDiv funded sWEEP working group, led by Prof. Miguel Ángel Olalla-Tárraga and Dr. Ignacio Morales-Castilla. The working group bought together researchers from the fields of Macroecology, Macroevolution and Macrophysiology working across aquatic and terrestrial realms in order to derive a set of phylogenetic comparative analyses, designed to disentangle the relative importance of the mechanisms invoked to explain the evolution of thermal tolerances (for an explanation of the hypotheses and tests see MS). Once the meeting was over and everyone went home, the task of leading this work was mine. But first to perform the comparative tests a dataset of comparable thermal tolerance limits for species from across the tree of life was needed.

Example of physiological experiment measuring thermal tolerance limits in springtail species that are able to resist under extreme cold conditions in Antarctica (Photo Credit.

I spent over a year scrutinizing, homogenizing and assembling data on thermal physiological traits from sources that were scattered throughout the literature. The resultant database Globtherm published in Scientific data is the largest publicly available thermal physiology dataset comprising over 2,000 wild species, alongside information on phylogentic relatedness and experimental methodologies for terrestrial, freshwater, and marine multicellular algae, plants, fungus, and animals. The dataset was specifically designed to be as comparable as possible to answer the questions being addressed by this study. Once the dataset was finished I was able to apply for a sDiv writing retreat grant so that a subset of the sWEEP group could meet in Madrid, Spain to discuss our exciting results!

sWEEP writing retreat Madrid. Meeting was held at Universidad Rey Juan Carlos and MNCN. From left to right Brezo Martínez Jennifer Sunday, Miguel Ángel Olalla-Tárraga, Ignacio Morales Castilla, Fabricio Villalobos, Miguel Araújo, Joanne Bennett (Photo Credit. Miguel Araújo).

In our paper published in Nature communications we show perhaps unsurprisingly that where a species currently lives is a strong determinate of their thermal tolerance. It makes sense that a species that lives in hot environment would be able to better tolerate heat than a species that lives in a cold environment and vice versa. In land plants and ectothermic animals, which are those that regulate their body temperature using external heat sources, we found that species with ancestors that lived at a time when earth was glaciated are more tolerant of cold than species with ancestors that lived at a time when earth was warm. We did not find this trend in endothermic animals, which are those that generate metabolic heat to regulate their own body temperature. We found that tolerance to cold has evolved twice as fast as tolerance to heat, likely due to physiological barriers to the evolution of heat tolerance. This is something I find very concerning because it suggests that given the past pace of evolution the vast majority of species will not be able to adapt fast enough to survive the unprecedented rate of contemporary climate change.

Many desert species have high thermal tolerance, examples in GlobTherm Melophorus bagoti (Photo Credit. Farhan Bokhari) and Larrea tridentata (creosote bush) in Red Rock Canyon, Nevada, (Photo Credit. Stan Shebs).


The strength of the activity is its depth and interdisciplinary approach. This activity reinforces the interdisciplinary nature of modern science. Students utilize real data from real scientists. Students apply the principles of evolution in their reasoning to make use of this data from geology and biological science. This activity originated at Princeton University in the summer of 1995 while I was a participant in the Woodrow Wilson National Foundation Institute on Biology. Though now modified, it was written as part of a biology module on evolution called “Evolution: A Context for Biology.” My original intent was to write a similar activity on Galapagos Finches, but that proved to be too complex and DNA mapping data had yet to be published.

For purposes of this publication, I have placed the student activity in the beginning followed by teacher information and my discussion of possible solutions.


Background — Figure 1 (left) illustrates one of the many populations of lizards living on the Canary Islands. The Canary Islands form an archipelago of seven volcanic islands just west of the African continent (Map 1). The island chain starts about 85 km (50 miles) west of the continent, following a fault line of the Atlas Mountains in northern Africa. Geologists theorize that a geologic hot spot of upwelling magma has been drifting westward for the past 20 million years, gradually forming the islands as it moves. Thus the most eastern island, Lanzarote, is oldest, while the smaller western island, Hierro, is the youngest, about 0.8 million years old. Volcanic islands are particularly good laboratories for evolutionary science because they can be dated accurately using radioactive isotope decay and because they start out as lifeless masses of rock emerging from the sea.

The development of ecosystems on volcanic islands is somewhat unpredictable. However, ecological succession does occur first with pioneer organisms that gradually alter the environment until a stable climax community is established. What is unpredictable is what plant and animal species will colonize these new environments. Much of this is left to climate, proximity to other land masses, and of course, chance. This investigation deals with three species of lizards of the genus Gallotia, and within one of these species, Gallotia galloti, four separate island populations. The arrival of the Gallotia lizards was probably by rafting (See Map 1). Rafts of natural vegetation are often washed out to sea when high river levels cause river banks to collapse, carrying away both plants and clinging animals. Oceanic currents in this region vary with the seasons. Colonization by airborne organisms, such as insects and birds, usually occurs during storms. In any case, there are some general principles of island colonization:

1) The closer the island to another land mass, the higher the probability of colonization.
2) The older the island, the more likely it will be colonized.
3) The larger the island, the more species are likely to be established.
4) Geographic isolation reduces gene flow between populations.
5) Over time, colonial populations become genetically divergent from their parent population due to natural selection, mutation, and/or genetic drift.
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Problem — Evolution biologists have been faced with an interesting problem. What is the phylogenetic history of the three species and seven populations of Gallotia lizards on the Canary Islands? Does the presence of four morphologically different populations of G. galloti on the four westernmost islands (Map 2) imply continuing evolution? In this investigation, you will use data from geography, geological history, morphology (body size), and molecular genetics to develop answers to these questions.

1) Which island is most likely to have been colonized first and which last? Tell why you think so.

2) Using Map 2 (download a pdf version—includes Table 1 below) and your geographic reasoning, draw on a separate page a hypothetical phylogenetic (family) tree of the three species and the three additional populations of G. galloti. Your teacher will demonstrate how to draw a phylogenetic tree. Label your end branches with the following population names:

atlantica stehlini galloti

Table 1. Maximum age of the Canary Islands in millions of years. (Anguita et al., 1986)

Lanzarote &
Gran Canaria Tenerife Gomera Palma Hierro
24.0 17.1 15.1 5.3 2.0 0.8

1) Explain how the data in Table 1 (above) support your phylogeny diagram? Or what changes should you make and why?
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Compare your two phylogeny charts. Describe how they are different.

Thorpe and his colleagues used restriction enzymes to cut the DNA, and gel electrophoresis to separate the fragments. Radioisotope tagging eventually led to the sequencing of the samples of DNA for each of the seven populations. Thorpe tested two populations on Tenerife to see if ecological differences were part of the story. He felt that because Tenerife is moist and lush in the north while arid and barren in the south, populations on that island might have some genetic differences. Also, he wondered if Tenerife was supplying colonizing lizards from two different directions. The results for Thorpe’s tests appear on the last two pages of this investigation.
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Your task is to count the differences between all pairings of the seven populations and use that data to construct a final phylogenetic tree based on genetic similarities and differences.

Procedure — There are 21 different pair combinations possible using seven populations. You should work in a team of four. Each person will be responsible for counting all of the base differences for five of the 21 pairs (see chart below). The pairings are listed on Table 2 (download a pdf version). Note that the first pairing has been counted for you. Record your results in Table 2. When all teams are done, the data will be checked for agreement. The easiest way to make accurate counts is to cut the paper into four strips and tape them end to end in the correct order, A to D. You will then compare pairs of strips side by side to count the differences.

There are 21 possible pairings, each team member selects five pairings other than 1/2.

Student #1 Student #2 Student #3 Student #4
1/3 1/4 1/5 1/6
1/7 2/3 2/4 2/5
2/6 2/7 3/4 3/5
3/6 3/7 4/5 4/6
4/7 5/6 5/7 6/7


Low numbers express more genetic similarity and imply more recent common ancestry. Pairs with high numbers are said to have greater genetic distance between them. In other words, large numbers imply they are less genetically alike, have more distant ancestry, and have been separated longer. On a phylogenetic tree, early ancestry is expressed by low branches while more recently evolved are on the higher branches. Branches that are far apart imply greater genetic distance.
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1) In Table 2, large numbers imply that pairs of populations are less related. Why is this?
2) Among the six populations, there are three species. How many base pair differences is the minimum to separate any two species of these lizards? (Remember, don’t confuse populations with species.) Give an example to support your answer.
3) Which two populations are most closely related? Justify your answer.
4) Why should you expect the populations S. Tenerife (ST) and N. Tenerife (NT) to have fewer differences than other pairings?
5) Which population is least related to the rest? Why do you say so?
Refer to your last phylogeny chart using genetic similarities and differences found in Table 2. Compare it to the phylogeny chart you drew based on the geographic distances and geologic age of the islands.
6) What difference is there between the two phylogenies?
7) Which species, G. stehlini or G. atlantica, is the ancestor of the other? Explain your reasoning.
8) Predict what is likely to happen to the four populations of G. galloti on the four westernmost islands. State what conditions will support this prediction.

Table 3. Base-pair sequences from the mitochondrial genome for cytochrome b of Gallotia species and populations. Island codes in parentheses are P = Palma, NT = north Tenerife, ST = south Tenerife, G = gomera, and H = Hierro. Each sequence consists of four lines, e.g., 1a+1b+1c+1d is the sequence for Gallotia stehlini. (Data from Thorpe et al., 1994). Download a pdf version..
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The final activity will be to use the results from the pairings to compare the differences, and use this information to develop a final phylogeny chart. The solutions are provided below. The diagrams appear to be cladograms, but technically, they are not. Their similarity to cladograms is more related to their ease in drawing. The basic scheme is that low numbers of base pair differences imply closer evolutionary relationships. The phylogeny charts are intended to stimulate student thinking about the problems of understanding past and future evolution. There are many variations to phylogenies students can come up with, some better than others. The criteria should really be: can the solution be logically explained and justified. Only the last phylogeny based on both molecular genetics and biogeography has fewer variations and needs some serious discussion to close the subject. Finally, most questions on this assignment cannot be answered without student explanation. You should emphasize that answers may vary, but logic is required for all solutions.
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The information that follows is intended as a guide to solutions to the phylogenies based on different types of data. These are my interpretations and are by no means definitive.

At left is one possible solution (download a pdf version of all three solutions pictured here) based on geographical distance and island hopping. It does not take into account actual currents which vary over time. There can be other reasonable solutions. The idea here is to get the student thinking about the logic of the problem, not its ultimate answer. Then numbers indicate the chronological sequence.
At left is a possible solution using island distribution and morphology. In using body size, one is tempted to guess that medium lizards of Palma could have been the immediate ancestors to Gomera and the small lizards of Gomera are ancestors to the small lizards of Hierro. This could contradict the argument based on distance. Again, there is no one perfect answer. Ecologists and geneticists have debated several hypotheses for years. Numbers imply chronology.
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The solution at left uses DNA evidence from Table 2 (completed table below— or download a pdf version) to deduce genetic distance. It is considered the most reliable criterion to establish evolutionary kinship. All base pairs have an equal chance for mutation and mutation rate is relatively constant, even though evolution rate is not. Note that north and south Tenerife populations are listed as one. Either may be a source for new colonization. The real surprise here is not the evolution of the smaller forms, it is that stehlini on Gran Canaria appears to have the oldest ancestry, although atlantica is actually closer to Africa. This unexpected surprise could support the hypothesis that the Gallotia lizard ancestor is European! As an extension, have students investigate the currents along the Portugal coast.

ANSWERS TO INTERPRETATIONS AND CONCLUSIONS 1) In Table 2, large numbers imply that pairs of populations are less related. Why is this? Large numbers imply distant ancestry because the longer two populations have been separated the more opportunity there has been for mutations.

2) Among the six populations, there are three species. How many base pair differences is the minimum to separate any two species of these lizards? (Remember, don’t confuse populations with species.) Give an example to support your answer. G. galloti on S. Tenerife has just 19 base pair differences from G. atlantica.

3) Which two populations are most closely related? Justify your answer. The G. galloti populations on Gomera and Hierro must be the most closely related because there are just four base pairs that are different.

4) Why should you expect the populations S. Tenerife (ST) and N. Tenerife (NT) to have fewer differences than other pairings? The S. Tenerife and N. Tenerife are just different populations on the same island, so I would expect some gene flow to occur, thus reducing differences between them.

5) Which population is least related to the rest? Why do you say so? G. stehlini is the population least related to the rest. The evidence is that G. stehlini had more genetic differences from all others, from 36 to 49!

Refer to your last phylogeny chart using genetic similarities and differences found in Table 2. Compare it to the phylogeny chart you drew based on the geographic distances and geologic age of the islands.

6) What difference is there between the two phylogenies? The big difference is which population is oldest. The last phylogeny suggests G. stehlini, not G. atlantica, which is closest to Africa.

7) Which species, G. stehlini or G. atlantica is the ancestor of the other? Explain you reasoning. G. stehlini is the ancestor to G. atlantica because stehlini has more genetic differences from the others than atlantica. It is also possible that both came from Africa independently at different times or even from Europe.

8) Predict what is likely to happen to the gene pools of the four populations of G. galloti on the four westernmost islands. State what conditions will support this prediction. I expect that each island population will continue to evolve to be a separate species because they are geographically isolated and mutations will continue to add up until they will become reproductively isolated as well.


Thorpe, R.S., and R.P. Brown. 1989. Microgeographic variation of the colour pattern of Canary Island lizard, Gallotia galloti within the island of Tenerife: distribution, pattern and hypothesis. Biological Journal of the Linnean Society 38:303�.

Thorpe, R.S., D.P. McGregor, and A.M. Cumming. 1993. Population evolution of Canary Island lizards, Gallotia galloti: four base endonuclease restriction of fragment length polymorphisms of mitochondrial DNA. Biological Journal of the Linnean Society 49:219– 227.

Thorpe, R.S., R.P. Brown, M. Day, A. Malhotra, D.P. McGregor, and W. Wuster. 1994. Testing ecological and phylogenetic hypotheses in microevolutionary studies. Pp. 189� in E.P. Eggleton and R. Vane-Wright (eds.), Phylogenetics and Ecology. Academic Press, London.

Thorpe, R.S., D.P. McGregor, A.M. Cumming, and W.C. Jordan. 1994. DNA evolution and colonization sequence of island lizards in relation to geological history. Evolution 48:230�.
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Map 1 redrawn from the Journal of Volcanology and Geothermal Research 30:155�: F. Anguita and F. Hernan. 1986. Geochronology of some Canarian dike swarms: contribution to the volcano- tectonic evolution of the archipelago. With the kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.

Origins of Evo-Devo

I go back to the late nineteenth century when we find the origins of evo–devo in the research of individuals in England (largely Trinity College, Cambridge) and in Continental Europe. These evolutionary morphologists/evolutionary embryologists were attracted to this research following the publications of The Origin of Species by Charles Darwin (Darwin 1859) and Ernst Haeckel’s theory that ontogeny recapitulates phylogeny (Haeckel 1866). Paradoxically, the first published study testing Darwin’s theory using embryos and larvae—Fritz Müller’s study of crustacean life histories (Müller 1864)—showed that ontogeny could be used to understand patterns of evolutionary history (phylogeny) and that mechanisms could be sought in ontogeny. So varied were crustacean life history strategies found to be that Müller found he could use the details and varieties of life history stages to construct a phylogeny of crustacean relationships. Haeckel took exactly the opposite position. Haeckel theorized that phylogeny explains ontogeny and erected his Biogenetic Law on this basis.

Embryos provided the way to study evolution. The fossil record was incomplete. Embryos, on the other hand, recorded in their development the history of their ancestors. This history had to be read with great care there were gaps in the record, and secondary specializations such as the placenta could confuse the unwary (Bowler 1996 Hall 1999). Nevertheless, from the late 1860s or early 1870s until the mid-1880s, evolutionary embryology was the field that attracted the brightest and best zoologists. It attracted those who wanted to study embryos in the laboratory or field station and those who wanted to seek embryos of such ‘missing links’ as the platypus (thought to link reptiles and mammals), lungfish (thought to link fish and tetrapods), and the velvet worm Peripatus (thought to link insects and arthropods) in such exotic places as Australia, South America and Africa (Hall 1999, 2001 MacLeod 1994 Bowler 1996 Laubichler and Maienschein 2007). William Bateson, the English zoologist who coined the name “genetics,” began his career as an evolutionary embryologist. Reminiscing on his career, Bateson commented that

Morphology was studied because it was the material believed to be the most favorable for the elucidation of the problems of evolution, and we all thought that in embryology the quintessence of morphological truth was most palpably presented. Therefore every aspiring zoologist was an embryologist, and the one topic of professional conversation was evolution. (Bateson 1922, p. 56)

Frustration with reconstructing evolutionary trees from embryonic sequences, the rise of experimental and physiological approaches to embryonic development in the 1880s, and the rediscovery of Mendelian genetics in 1900 all cast evolutionary embryology into a backwater from which it would take a century to resurface. Mendel’s principles of segregation and assortment coupled with studies on the fruit fly Drosophila provided a powerful foundation upon which the new science of genetics was built. Publication of Dobzhansky’s (1937) influential book, “Genetics and the Origin of Species,” provided a basis for understanding evolution through population genetics, the mathematical models for which have been developed in the 1920.

By the middle of the twentieth century, maintenance of the features of organisms, variation in those features, and the origin of new features all seemed explicable by a fusion of Mendelian and population genetics. Paradoxically, the use of Drosophila as the model organism for genetics eliminated the roles of embryonic development and of the environment from evolutionary discussion and theory inbred laboratory organisms display none of the variation and adaptability seen in nature.

Mammal Diversity

Welcome to Mammal Diversity, the Burke Museum’s exploration of the diversity of Earth's mammals. Our tree diagram, down below, shows you the pathways of relatedness and historical evolution of today’s 29 different mammal orders. This phylogenetic tree also shows you that all of our modern mammals were derived from a common ancestor that lived over 200 million years ago. Click on each order for photos and a who’s–who of its members.

Mammals belong to the group of animals that have a backbone, or column of vertebrae. These vertebrate animals include various fishes, amphibians, reptiles, birds, and mammals. The vertebrates all descended from a common ancestor that lived over half a billion years ago. The Class Mammalia evolved later in the history of life on Earth, in the early Mesozoic, about 210 million years ago. Today we find mammals across all of Earth’s continental land masses, on the ground, in the ground, above the ground, and in the air, as well as throughout the oceans. Scientists recognize more than 5,400 species of mammals world–wide.

What distinguishes mammals from other vertebrates? Mammals have hair on their bodies for insulation and protection. Most of them have quite a bit of hair, but some, like whales, armadillos, and humans don’t have so much. Mammal mothers provide their newborn with milk from their mammary glands. Three special tiny bones (the hammer, anvil, and stirrup) that conduct sound through the middle ear of mammals to the hearing nerve in the inner ear also represent unique mammalian characteristics. Mammals also have a single lower jaw bone (the dentary) on each side of their jaw. In fossil mammals, we can’t find hair or milk, but we can identify these special bones that are only found in the mammalian skull.

The branching diagram above is a phylogenetic tree of modern mammals, showing how all modern mammals are related to one another. It is based on available scientific evidence for the evolutionary relationships among major living groups (orders) of mammals. The most recent common ancestor of all mammals lived about 210 million years ago, indicated by the black dot at the base of the tree. The earliest mammals descended from reptile ancestors. They were small, land–inhabiting creatures, not completely like the mammals alive today. Rocks from the Triassic (earliest) period of the Mesozoic era contain these fossil records. These earliest mammals laid eggs, just as reptiles do. Among today’s mammals only the platypus and the echidnas (Order Monotremata) lay eggs to produce their young but, being mammals, they nourish their hatchlings with milk. Monotremes are the oldest of modern orders. Throughout the first 100 million years of their 210–million year history, mammals were basically small, generalized land–dwelling creatures. Compared to reptiles, mammals were few in number and probably many of them were active during the night. Among the earliest groups of modern mammals to evolve were the ancestors of today’s marsupials. These appeared in the fossil record during the later Mesozoic, in the Cretaceous, which is the time of the dinosaurs. Marsupials give birth to tiny, very immature young that are nourished with milk for a long developmental period during the early stages of this development the young are continuously attached to their mother’s teats in a pouch (marsupium). Three orders of marsupial mammals (Didelphimorphia, Paucituberculata, Microbiotheria) live today in South and Central America (and marginally in North America). Four orders of the best known and most diverse marsupials are found in Australasia (Australia, New Guinea, and nearby islands). These are: Diprotodontia, Peramelemorphia, Dasyuromorphia, Notoryctemorphia. During the early evolutionary history of marsupials the present continents of Australia, Antarctica, and South America were joined, as part of the massive southern continent “Gondwana”.

The remaining 21 modern orders of mammals (often called the Eutherian mammals) branched off from one another relatively rapidly around 70 to 50 million years ago. This rapid diversification is recognized, in evolutionary terms, as an adaptive radiation. This means that mammals expanded the range of body forms and ways of making a living, or niches, by which species were able to survive. The resulting great variety of body forms, modes of locomotion, diets, skull forms, and dental anatomy that we see today mostly arose during this rapid radiation in the early Cenozoic, or early Paleogene. By the time of the Eocene and Oligocene epochs, mammals were represented by modes of locomotion that included not only walking, but running, crawling, hopping, climbing, gliding, and even flying and swimming. They came to occupy many ecological niches and every geographic corner of Earth. The whales and dolphins (Cetacea) represent one of the most dramatic of these evolutionary transformations. As descendants of the small, terrestrial, four–legged Mesozoic mammalian ancestors, whales developed new adaptations in the early Paleogene and took on a new body form, including loss of the hind limbs. With front limbs that evolved into flippers and with their fish–like body form, the Cetaceans became swimmers and divers. This evolutionary process allowed them to return successfully from the life of their mammal ancestors on land to the seas, inhabited by their much earlier ancient fish ancestors. Whales include the largest mammal species. Furthermore the largest animal of any kind, including dinosaurs, ever known to have lived on Earth, is the Blue Whale.

The adaptive radiation of modern mammals in the Cenozoic era resulted in the great variety of body forms and modes of locomotion that suit mammals for life in all of Earth’s major environmental media–land, water, and air. Depending on where it lives, an animal has different requirements for moving itself around (locomotion). The same general body plan and common set of bones in the skeletons of the early mammal ancestors have evolved into the diverse array of modern body forms. For example, the same bones of the arm or foreleg are modified into elongated running legs in hoofed mammals, into wings in bats, flippers in whales, and even “shovels” in moles. These and other evolutionary changes in mammals have all occurred since the time when the earliest common ancestors of today’s mammals derived the historic first characteristics that distinguished them from reptiles.

The diets, feeding behavior, and ecology of mammals have influenced the evolution of the shape of the skull and kinds of teeth in the jaws. Mammals use their teeth to seize and, in the case of some predators, to kill their food. Also, unlike many other kinds of animals, mammals use their jaws and teeth to break up and chew pieces of their food that are then further digested in the stomach. (Have you ever seen a bird, a reptile, or an amphibian chewing food?) Most mammals have a variety of different kinds of teeth in their jaws–incisors, canines, premolars, and molars. The numbers, shapes, and sizes of these different kinds of teeth, as well as the shape of the skull have become matched to deal with the feeding behavior and kind of food eaten by each species. Special extreme cases are also interesting. The tropical American anteaters have no teeth at all. An anteater just uses its tongue to slurp up ants and termites. Some of the biggest whales also have no teeth, but instead their mouths contain the brush–like filtering material called “baleen.” This material is used to pick up small shrimp–like “krill” that the so–called baleen whales filter from seawater. Mammals that are specialized for plant–eating (herbivory), whether they are small rodents or large elk, antelopes, or zebras, have flat, hard–ridged rear teeth (premolars and molars) that they use to grind grasses and other green browse plants. Specialized carnivores, such as members of the cat and dog families, have sharper, pointier rear teeth for piercing, tearing, and even shearing pieces of flesh. The longest and sharpest teeth in these carnivores are their canines. Other mammals such as humans, bears, and raccoons are omnivores and have more generalized rear teeth that are neither extremely flat nor extremely pointed they are, instead, somewhat flat, but with rounded bumps or “cusps.” The incisors, in the front of the mouth, are the first teeth to grab and in some cases to cut the food. The long and pointed canines are piercing teeth, used mainly by predatory meat–eating mammals in fact they are absent in most herbivores.

Most mammal females bear their young alive, but members of the order Monotremata (platypus and echidnas) lay eggs from which the young must hatch before they can be nourished by mother’s milk. Note that some other vertebrates, including some sharks, bony fishes, lizards, and snakes give birth to live young, rather than hatching eggs.

You have to travel around the world to see all the different kinds of mammals–kangaroos in Australia, giraffes in Africa, and mountain goats in North America. Why is this? The answer comes from knowing about Earth history. For example, the northern continents were joined together and the southern continents were joined together at the time of the early evolution of mammals, but then they became separated. This means that the new, smaller continents often maintained species that descended from common ancestors who originated on the big supercontinents. That’s how mammals now on different continents were able to share ancestry. At various times since then, connections have been reestablished between north and south. For example, North and South America were separated for a long time until they were reconnected at the “Panama Land Bridge” about 3 million years ago. These kinds of historic continental connections and reconnections explain the unevenness in the geographic diversity and evolutionary relatedness of mammals (and of course other organisms) across the globe. Although ancient Marsupials (a group of seven orders) have been recorded as fossils on most continents, their successes were greatest beginning at the time when South America, Antarctica, and Australia were connected today we still find the greatest successes in Australia and South America–a heritage of the great late Cretaceous supercontinent of Gondwana. Over the entire Earth, scientists now recognize 29 different orders that make up the Class Mammalia. In Washington we have only nine of these orders, or just less than one–third of the world’s mammal biodiversity in terms of orders. In terms of species, the State of Washington has 141 species of mammals, which is just less than three percent of the 5400 mammal species found on Earth.

“Mammal Diversity” web design, graphics, images, and production by George Wang, May 2009.

Any species returning to the land twice throughout their evolution? - Biology

The first thing to notice on this evogram is that hippos are the closest living relatives of whales, but they are not the ancestors of whales. In fact, none of the individual animals on the evogram is the direct ancestor of any other, as far as we know. That's why each of them gets its own branch on the family tree.

Hippos are large and aquatic, like whales, but the two groups evolved those features separately from each other. We know this because the ancient relatives of hippos called anthracotheres (not shown here) were not large or aquatic. Nor were the ancient relatives of whales that you see pictured on this tree — such as Pakicetus. Hippos likely evolved from a group of anthracotheres about 15 million years ago, the first whales evolved over 50 million years ago, and the ancestor of both these groups was terrestrial.

These first whales, such as Pakicetus, were typical land animals. They had long skulls and large carnivorous teeth. From the outside, they don't look much like whales at all. However, their skulls — particularly in the ear region, which is surrounded by a bony wall — strongly resemble those of living whales and are unlike those of any other mammal. Often, seemingly minor features provide critical evidence to link animals that are highly specialized for their lifestyles (such as whales) with their less extreme-looking relatives.

Compared to other early whales, like Indohyus and Pakicetus, Ambulocetus looks like it lived a more aquatic lifestyle. Its legs are shorter, and its hands and feet are enlarged like paddles. Its tail is longer and more muscular, too. The hypothesis that Ambulocetus lived an aquatic life is also supported by evidence from stratigraphy — Ambulocetus's fossils were recovered from sediments that probably comprised an ancient estuary — and from the isotopes of oxygen in its bones. Animals are what they eat and drink, and saltwater and freshwater have different ratios of oxygen isotopes. This means that we can learn about what sort of water an animal drank by studying the isotopes that were incorporated into its bones and teeth as it grew. The isotopes show that Ambulocetus likely drank both saltwater and freshwater, which fits perfectly with the idea that these animals lived in estuaries or bays between freshwater and the open ocean.

Whales that evolved after Ambulocetus (Kutchicetus, etc.) show even higher levels of saltwater oxygen isotopes, indicating that they lived in nearshore marine habitats and were able to drink saltwater as today's whales can. These animals evolved nostrils positioned further and further back along the snout. This trend has continued into living whales, which have a "blowhole" (nostrils) located on top of the head above the eyes.

These more aquatic whales showed other changes that also suggest they are closely related to today's whales. For example, the pelvis had evolved to be much reduced in size and separate from the backbone. This may reflect the increased use of the whole vertebral column, including the back and tail, in locomotion. If you watch films of dolphins and other whales swimming, you'll notice that their tailfins aren't vertical like those of fishes, but horizontal. To swim, they move their tails up and down, rather than back and forth as fishes do. This is because whales evolved from walking land mammals whose backbones did not naturally bend side to side, but up and down. You can easily see this if you watch a dog running. Its vertebral column undulates up and down in waves as it moves forward. Whales do the same thing as they swim, showing their ancient terrestrial heritage.

As whales began to swim by undulating the whole body, other changes in the skeleton allowed their limbs to be used more for steering than for paddling. Because the sequence of these whales' tail vertebrae matches those of living dolphins and whales, it suggests that early whales, like Dorudon and Basilosaurus, did have tailfins. Such skeletal changes that accommodate an aquatic lifestyle are especially pronounced in basilosaurids, such as Dorudon. These ancient whales evolved over 40 million years ago. Their elbow joints were able to lock, allowing the forelimb to serve as a better control surface and resist the oncoming flow of water as the animal propelled itself forward. The hindlimbs of these animals were almost nonexistent. They were so tiny that many scientists think they served no effective function and may have even been internal to the body wall. Occasionally, we discover a living whale with the vestiges of tiny hindlimbs inside its body wall.

This vestigial hindlimb is evidence of basilosaurids' terrestrial heritage. The picture below on the left shows the central ankle bones (called astragali) of three artiodactyls, and you can see they have double pulley joints and hooked processes pointing up toward the leg-bones. Below on the right is a photo of the hind foot of a basilosaurid. You can see that it has a complete ankle and several toe bones, even though it can't walk. The basilosaurid astragalus still has a pulley and a hooked knob pointing up towards the leg bones as in artiodactyls, while other bones in the ankle and foot are fused. From the ear bones to the ankle bones, whales belong with the hippos and other artiodactyls.

The Institute for Creation Research

Ever since Darwin, the concept of natural selection has dominated evolutionary thought, providing a "naturalistic" explanation for the origin of species, and thus (as Julian Huxley used to say) eliminating the need for God. In recent years, however, there has been a strong reaction against Darwinian evolution in many places. Unfortunately, the change has not caused these scientists to return to creationism, but instead, to pre-Darwinian evolutionism. That is, they are abandoning atheistic evolution and returning to pantheistic evolution. In fact, this is the pseudo-scientific rationale underlying the so-called New Age Movement which is sweeping over the world today.

Evolutionism is not a modern scientific theory at all, but is as old as human rebellion against the Creator.

That "basic substance" out of which all things have evolved is said to have been the primeval watery chaos which had existed from eternity. From this evolved the gods and goddesses who produced everything else. This universal belief of antiquity is not just primitive mythology, of course.

Dr. Stanley Jaki, with doctorates in both physics and theology and author of 32 books, confirms the universality of ancient pagan evolutionism:

As far as the post-Flood world is concerned, this pagan evolutionism originated in ancient Babylon, in the land of Sumer, but then spread around the world with the dispersion, as described in Genesis 11. It came to full flower in Greece, especially through the writings of Homer and Hesiod.

The earth itself was known as the mother of all living things. The Greek goddess of the earth, Gaia (with equivalent names in other ethnic religions), soon became recognized as "Mother Earth" or "Mother Nature."

The author cited above is a brilliant scientist and is one of the leaders in developing the modern "Gaian Hypothesis," which views the earth as an actual living organism, evolving itself while controlling the geological evolution of its crust and the biological evolution of its plants and animals.

Lovelock and other leading Gaians do not think of Gaia as a real woman living on Mount Olympus or somewhere, but as a living, intelligent "being" comprising the earth and all its evolving organisms and other systems.

Another distinguished scientist advocating evolutionary pantheism is Rupert Sheldrake with a Ph.D. from Cambridge University, and later director of studies in cell biology there.

As Dr. Sheldrake indicates, the modern "green movement," which is rapidly growing all over the world, is largely committed to this concept of pantheistic evolution. In fact, the environmental activists in politics, both local and national, are strongly influenced by such ideas.

This theme is being continually emphasized in public school classrooms today and, with the recent election results, is almost certain to become a major theme in the new federal administration. This is a reasonable assumption based on the selection of a vice president whose best-selling 1992 book, "Earth in the Balance: Ecology and the Human Spirit" is so passionately devoted to such concepts.

The worship of "Mother Earth" is also becoming prominent in some aspects of the modern feminist movement. The more radical feminists, in fact, are replacing God with "The Goddess," even holding worship services in "her" name. In fact, Vice-President-Elect Al Gore, on page 260 of his book, cites with approval the statement that "the prevailing ideology of belief in prehistoric Europe and much of the world was based on the worship of a single earth goddess," lamenting the fact that "organized goddess worship was eliminated by Christianity."

In fact, the idea of pantheistic evolution is not even limited to that of Earth and its systems. Modern New Agers embrace the whole universe in some form of conscious cosmic evolution. The famous astronomer Fred Hoyle, in fact, has written an entire book entitled, "The Intelligent Universe" (London: Michael Joseph Co., 1983), rejecting terrestrial Darwin-type evolution in favor of cosmic pantheistic evolution. Another British astronomer and physicist, Paul Davies, thinks that modern notions of "order from chaos" somehow prove that the "creative cosmos" has created itself.

Then, continuing, he proves this merely by citing:

Dr. Davies neglects to explain, however, just how the DNA was ever programmed to do this. Perhaps Mother Nature did it! In any case, this is exactly what more and more scientists believe today.

It is not possible in our limited space to discuss this further, but the fact is that there is no more scientific proof (or even real evidence) for pantheistic evolution than for atheistic evolution. Evolution in any form is nothing but "cunningly devised fables" and "science falsely so-called."[11]

As the Catholic physicist, Dr. Wolfgang Smith has said:

Just as pantheistic evolution served as the world's religion in the early days, so it will do again in the last days. The New Age is really nothing but a revival in modern garb of the Old Age&mdashthat is, the first age after the Flood, when King Nimrod led the world in a united rebellion against the Creator. [13] And just as all the groups in the wide spectrum of New Age beliefs are founded upon a base of pantheistic evolutionism, so all have as their ultimate goal, just as Nimrod did, the development of a global system of government, culture, finance, and religion. The United Nations Organization is currently the focus of these plans, but it will eventually "evolve" into a much stronger international government in which all "the kings of the earth (will) set themselves, and the rulers take counsel together, against the LORD, and against His [Christ], saying, Let us break their bands asunder, and cast away their cords from us" (Psalm 2:2,3).

To accomplish this, they must first teach men once again (as they did in ancient time) to change "the glory of the incorruptible God into an image made like to corruptible man," and then to "[worship] and [serve] the creature more than the Creator" (Romans 1:23,25). As Robert Muller, former Assistant Secretary General of the United Nations (presumably speaking on behalf of that organization) has said:

Now, if the most fundamental thing that New Agers (as well as the older style secular humanists and social Darwinists) can do to bring about such a world system is to believe in evolution, that means the most effective thing the remnant of believers in God and His Word can do to offset this is to believe and teach a soundly Biblical and scientific creationism. This must include the great truth that the Creator has now also become the Lamb of God, our sin-forgiving Savior, and soon will return as eternal King.

In that day, "These shall make war with the Lamb, and the Lamb shall overcome them: for He is Lord of lords, and King of kings" (Revelation 17:14).

* Dr. Henry M. Morris is Founder and President Emeritus of the Institute for Creation Research.

Seasonality in spatial distribution: Climate and land use have contrasting effects on the species richness of breeding and wintering birds

Kazuhiro Kawamura, Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Kitaku Kita 9 Nishi 9, Sapporo, Hokkaido 060-8589, Japan.

Department of Forest Vegetation, Forestry and Forest Products Research Institute, Tsukuba, Japan

Fenner School of Environment and Society, Australian National University, Canberra, Australian Capital Territory, Australia

Shikoku Research Center, Forestry and Forest Products Research Institute, Asakuranishi, Kochi, Japan

Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan

Biodiversity Assessment and Projection Section, Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba City, Japan

Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido, Japan

Japan Bird Research Association, Tokyo, Japan

Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan

Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan

Kazuhiro Kawamura, Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Kitaku Kita 9 Nishi 9, Sapporo, Hokkaido 060-8589, Japan.

Department of Forest Vegetation, Forestry and Forest Products Research Institute, Tsukuba, Japan

Fenner School of Environment and Society, Australian National University, Canberra, Australian Capital Territory, Australia

Shikoku Research Center, Forestry and Forest Products Research Institute, Asakuranishi, Kochi, Japan

Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan

Biodiversity Assessment and Projection Section, Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba City, Japan

Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido, Japan

Japan Bird Research Association, Tokyo, Japan

Department of Forest Science, Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan

Data Availability Statement:: The data of survey site distribution, bird species richness, and environment are available at Dryad Digital Repository:


Many studies have examined large-scale distributions of various taxa and their drivers, emphasizing the importance of climate, topography, and land use. Most studies have dealt with distributions over a single season or annually without considering seasonality. However, animal distributions and their drivers can differ among seasons because many animals migrate to suitable climates and areas with abundant prey resources. We aim to clarify seasonality in bird distributions and their drivers.



We examined the effects of climate (annual mean temperature, snow depth), topography (elevation), and land use (extent of surrounding habitat) on bird species richness, in the breeding and wintering seasons separately, using nationwide data (254 forest and 43 grassland sites, respectively). We separately analyzed the species richness of all species, residents, short-, and long-distance migrants in forests and grasslands.


In the breeding season, the annual mean temperature negatively affected all groups (except for forest and grassland residents), and the extent of surrounding habitat positively affected many groups. By contrast, in the wintering season, temperature positively affected all groups (except for forest residents), and the extent of surrounding habitat positively affected only grassland long-distance migrants. In both seasons, the species richness of forest and grassland residents was high in regions of moderate and high temperature, respectively. Moreover, snow depth negatively affected all forest groups in the wintering season. Mapping expected species richness suggested that regions with different climates served as habitats for different groups during different seasons.

Main conclusions

All regions were important bird habitats depending on the season, reflecting the contrasting effects of temperature across seasons. In the breeding season, surrounding land use was also an important driver. To understand the seasonal role that each region and environment plays in maintaining species/communities, a large-scale study considering both environmental seasonality and species distribution is needed.

Science, Evolution, and Creationism (2008)

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C h a p t e r O n e Evolution and the Nature of Science The scientific evidence supporting biological evolution continues to grow at a rapid pace. For more than a century and a half, scientists have been gathering evidence that expands our understanding of both the fact and the processes of biological evolution. They are investigating how evolution has occurred and is continuing to occur. In 2004, for example, a team of researchers made a remarkable discovery. On an island in far northern Canada, they found a four-foot-long fossil with features intermediate between those of a fish and a four-legged animal. It had gills, scales, and fins, and it probably spent most of its life in the water. But it also had lungs, a flexible neck, and a sturdy fin skeleton that could support its body in very shallow water or on land. Earlier scientific discoveries of fossilized plants and animals had already revealed a considerable amount about the environment in which this creature lived. About 375 million years ago, what is now Ellesmere Island in Nunavut Territory, Canada, was part of a broad plain crossed by many meandering streams. Trees, ferns, and other ancient plants grew on the banks of the streams, [Species: In sexual­ ly reproducing organ­ creating a rich environment for bacteria, fungi, and simple animals that fed on isms, species consist decaying vegetation. No large animals yet lived on the land, but Earth’s oceans of individuals that can contained many species of fish, and some of those species fed on the plants and interbreed with each animals in shallow freshwater streams and swamps. other.] Science, Evolution, and Creationism 

[Paleontologist: Paleontologists had previously found the fossils of some of these shallow- A scientist who water fishes. The bones in their fins were sturdier and more complex than in studies fossils to other fish species, perhaps allowing them to pull themselves through plant- learn about ancient filled channels, and they had primitive lungs as well as gills. Paleontologists organisms.] had also found, in somewhat younger sediments, fossils of fishlike animals that likely spent part of their time on land. Known as early tetrapods (a Paleontologists word referring to their four legs), they had modified front and back fins that searched this valley in Nunavut, near the resembled primitive legs and other features suited for life out of the water. But Arctic Circle in north paleontologists had not found fossils of the transitional animals between shal- central Canada, for low-water fishes and limbed animals. fossils when they learned that it con- The team that discovered the new fossil decided to focus on far northern tained sedimentary Canada when they noticed in a textbook that the region contained sedimentary rocks deposited dur- rock deposited about 375 million years ago, just when shallow-water fishes ing the period when were predicted by evolutionary science to be making the transition to land. The limbed animals were first starting to live team had to travel for hours in planes and helicopters to reach the site, and they on land. Fossils of could work for just a couple of months each summer before snow began to fall. Tiktaalik were dis- In their fourth summer of fieldwork they found what they had predicted they covered on the dark would find. In an outcropping of rock on the side of a hill, they uncovered the outcropping of rock on the right side of fossil of a creature that they named Tiktaalik. (The name means “big freshwater this photograph. fish” in the language of the Inuit of northern Canada.) Tiktaalik still had many site of fossils Tiktaalik’s left and right fins had a single upper bone (the large bone at the bot- tom of each of these drawings) followed by two intermediate bones, giving the creature an elbow and a wrist, as in more recent organisms.  Science, Evolution, and Creationism

Tiktaalik lived during the period when freshwa- ter fishes were evolving Ichthyostega the adaptations that enabled four-legged animals to live out of water. Tiktaalik may have Tiktaalik lived somewhat before or somewhat after the ancestral species that gave rise to all of today’s limbed animals, including Panderichthys humans. The evolution- ary lineage that contained Tiktaalik may have gone extinct, as shown in this diagram by the short line branching from the main evolutionary lineage, or it may have been part of the evolutionary line leading to all modern tetrapods (animals with four legs). The last com- mon ancestor of humans and all modern fishes also gave rise to evolution- ary lineages that led to modern lobe-finned fishes of the features of fish, but it also had traits characteristic of early tetrapods. (represented today by Most important, its fins contained bones that formed a limb-like appendage that the coelacanth). In this and succeeding figures, the animal could use to move and prop itself up. time is represented by the A prediction from more than a century of findings from evolutionary biol- lengths of the lines mod- ogy suggests that one of the early species that emerged from the Earth’s oceans ern groups of organisms about 375 million years ago was the ancestor of amphibians, reptiles, dino- are listed at the top of the figure. saurs, birds, and mammals. The discovery of Tiktaalik strongly supports that prediction. Indeed, the major bones in our own arms and legs are similar in overall configuration to those of Tiktaalik. The discovery of Tiktaalik, while critically important for confirming predic- tions of evolution theory, is just one example of the many findings made every year that add depth and breadth to the scientific understanding of biological evolution. These discoveries come not just from paleontology but also from physics, chemistry, astronomy, and fields within biology. The theory of evolu- tion is supported by so many observations and experiments that the overwhelm- ing majority of scientists no longer question whether evolution has occurred and continues to occur and instead investigate the processes of evolution. Scientists are confident that the basic components of evolution will continue to be sup- ported by new evidence, as they have been for the past 150 years. Science, Evolution, and Creationism 

Biological evolution is the central organizing principle of modern biology. [Trait: A physical The study of biological evolution has transformed our understanding of life or behavioral on this planet. Evolution provides a scientific explanation for why there are so characteristic of many different kinds of organisms on Earth and how all organisms on this plan- an organism.] et are part of an evolutionary lineage. It demonstrates why some organisms [DNA: Deoxyribo­ that look quite different are in fact related, while other organisms that may look nucleic acid. A biolog­ similar are only distantly related. It accounts for the appearance of humans on ical molecule composed Earth and reveals our species’ biological connections with other living things. It of subunits known details how different groups of humans are related to each other and how we as nucleotides strung acquired many of our traits. It enables the development of effective new ways together in long chains. to protect ourselves against constantly evolving bacteria and viruses. The sequences of these nucleotides contain the Biological evolution refers to changes in the traits of organisms over multiple information that cells generations. Until the development of the science of genetics at the beginning need in order to grow, of the 20th century, biologists did not understand the mechanisms responsible to divide into daughter for the inheritance of traits from parents to offspring. The study of genetics cells, and to manufac­ showed that heritable traits originate from the DNA that is passed from one ture new proteins.] generation to the next. DNA contains segments called genes that direct the pro- [Protein: A large duction of proteins required for the growth and function of cells. Genes also molecule consisting of orchestrate the development of a single-celled egg into a multicellular organism. a chain of smaller mol­ DNA is therefore responsible for the continuity of biological form and function ecules called amino across generations. acids. The sequence However, offspring are not always exactly like their parents. Most organ- of amino acids and isms in any species, including humans, are genetically variable to some extent. the molecule’s three- dimensional structure In sexually reproducing species, where each parent contributes only one-half determine a protein’s of its genetic information to its offspring (the offspring receives the full amount specific function in of genetic information when a sperm cell and an egg cell fuse), the DNA of the cells or organisms.] two parents is combined in new ways in the offspring. In addition, DNA can undergo changes known as mutations from one generation to the next, both in [Mutation: A change sexually reproducing and asexually reproducing organisms (such as bacteria). in the sequence of nucleotides in DNA. When a mutation occurs in the DNA of an organism, several things can Such changes can alter happen. The mutation may result in an altered trait that harms the organism, the structure of pro­ making it less likely to survive or produce offspring than other organisms in teins or the regulation the population to which it belongs. Another possibility is that the mutation of protein production.] makes no difference to the well-being or reproductive success of an organ- ism. Or the new mutation may result in a trait that enables an organism to [Population: A group of organisms take better advantage of the resources in its environment, thereby enhancing of the same species that its ability to survive and produce offspring. For example, a fish might appear are in close enough with a small modification to its fins that enables it to move more easily through proximity to allow shallow water (as occurred in the lineage leading to Tiktaalik) an insect might them to interbreed.]  Science, Evolution, and Creationism

acquire a different shade of color that enables it to avoid being seen by preda- tors or a fly might have a difference in its wing patterns or courtship behav- iors that more successfully attracts mates. If a mutation increases the survivability of an organism, that organism is like- ly to have more offspring than other members of the population. If the offspring inherit the mutation, the number of organisms with the advantageous trait will increase from one generation to the next. In this way, the trait — and the genetic material (DNA) responsible for the trait — will tend to become more common in a population of organisms over time. In contrast, organisms possessing a harmful or deleterious mutation are less likely to contribute their DNA to future generations, and the trait resulting from the mutation will tend to become less frequent or will be eliminated in a population. Evolution consists of changes in the heritable traits of a population of organisms as successive generations replace one another. It is populations of organisms that evolve, not individual organisms. The differential reproductive success of organisms with advantageous traits is known as natural selection, because nature “selects” traits that enhance [Natural selection: the ability of organisms to survive and reproduce. Natural selection also can Differential survival reduce the prevalence of traits that diminish organisms’ abilities to survive and reproduction of organisms as a and reproduce. Artificial selection is a similar process, but in this case humans consequence of the rather than the environment select for desirable traits by arranging for animals characteristics of the or plants with those traits to breed. Artificial selection is the process responsible environment.] for the development of varieties of domestic animals (e.g., breeds of dogs, cats, and horses) and plants (e.g., roses, tulips, corn). Evolution in Medicine: Combating New Infectious Diseases In late 2002 several hundred Immediately, work began on a people in China came down blood test to identify people with with a severe form of pneu- the disease (so they could be monia caused by an unknown quarantined), on treatments for infectious agent. Dubbed the disease, and on vaccines to “severe acute respiratory syn- prevent infection with the virus. drome,” or SARS, the disease An understanding of evolu- soon spread to Vietnam, Hong tion was essential in the identi- Kong, and Canada and led to fication of the SARS virus. The hundreds of deaths. In March genetic material in the virus 2003 a team of researchers at was similar to that of other the University of California, San viruses because it had evolved Francisco, received samples of from the same ancestor virus. a virus isolated from the tissues of a SARS patient. Furthermore, knowledge of the evolutionary history Using a new technology known as a DNA micro­ of the SARS virus gave scientists important informa- array, within 24 hours the researchers had identi- tion about the disease, such as how it is spread. fied the virus as a previously unknown member of Knowing the evolutionary origins of human patho- a particular family of viruses — a result confirmed gens will be critical in the future as existing infectious by other researchers using different techniques. agents evolve into new and more dangerous forms. Science, Evolution, and Creationism 

Evolution in Agriculture: The Domestication of Wheat When humans understand a phenomenon that wild wheat so that seeds remained on the plant occurs in nature, they often gain increased control when ripe and could easily be separated from their over it or can adapt it to new uses. The domesti- hulls. Over the next few millennia, people around cation of wheat is a good example. the world used similar processes of evolution- By recovering seeds from dif- ary change to transform many other ferent archaeological sites and wild plants and animals into the noticing changes in their char- crops and domesticated animals acteristics over the centuries, we rely on today. scientists have hypothesized In recent years, plant sci- how wheat was altered by entists have begun making humans over time. About hybrids of wheat with some 11,000 years ago, people of their wild relatives from in the Middle East began the Middle East and else- growing plants for food where. Using these hybrids, rather than relying entirely they have bred wheat varieties on the wild plants and ani- that are increasingly resistant mals they could gather or hunt. to droughts, heat, and pests. These early farmers began sav- Most recently, molecular biologists ing seeds from plants with particu- have been identifying the genes in larly favorable traits and planting those the DNA of plants that are responsible for seeds in the next growing season. Through this their advantageous traits so that these genes can process of “artificial selection,” they created a be incorporated into other crops. These advances variety of crops with characteristics particularly rely on an understanding of evolution to analyze suited for agriculture. For example, farmers the relationships among plants and to search for over many generations modified the traits of the traits that can be used to improve crops. Evolution can result in both small and large changes in populations of organisms. Evolutionary biologists have discovered structures, biochemical processes and pathways, and behaviors that appear to have been highly conserved within and across species. Some species have undergone little overt change in their body structure over many millions of years. At the level of DNA, some genes that control the production of biochemicals or chemical reactions that are essential for cellular functioning show little variation across species that are only distantly related. (See, for example, the DNA sequences for two different genes that are conserved in closely related as well as more distantly related species that are described on pages 30 and 31.) However, natural selection also can have radically different evolutionary effects over different timescales. Over periods of just a few generations (or,  Science, Evolution, and Creationism

in some documented cases, even a single generation), evolution produces relatively small-scale microevolutionary changes in organisms. For example, [Microevolution: many disease-causing bacteria have been evolving increased resistance to anti- Changes in the traits biotics. When a bacterium undergoes a genetic change that increases its ability of a group of organ­ isms that do not result to resist the effects of an antibiotic, that bacterium can survive and produce in a new species.] more copies of itself while nonresistant bacteria are being killed. Bacteria that cause tuberculosis, meningitis, staph infections, sexually transmitted diseases, and other illnesses have all become serious problems as they have developed resistance to an increasing number of antibiotics. Another example of microevolutionary change comes from an experiment on the guppies that live in the Aripo River on the island of Trinidad. Guppies that live in the river are eaten by a larger species of fish that eats both juveniles and adults, while guppies that live in the small streams feeding into the river are eaten by a smaller fish that preys primarily on small juveniles. The guppies in the river mature faster, are smaller, and give birth to more and smaller offspring than the guppies in the streams do because guppies with these traits are better able to avoid their predator in the river than are larger guppies. When guppies were taken from the river and introduced into a stream without a preexisting population of guppies, they evolved traits like those of the stream guppies within about 20 generations. Incremental evolutionary changes can, over what are usually very long Studies of guppies in Trinidad have demon- periods of time, give rise to new types of organisms, including new species. strated basic evolution- The formation of a new species generally occurs when one subgroup within a ary mechanisms. species mates for an extended period largely within the subgroup. For exam- ple, a subgroup may become geographically separated from the rest of the species, or a subgroup may come to use resources in a way that sets them apart from other members of the same species. As members of the subgroup mate among themselves, they accumulate genetic differences compared with the rest of the species. If this reproductive isolation continues for an extended period, How long could it take to produce 1,000 generations? How many generations might occur in a million years? 1 Generation 1,000 Generations Generations per 1 million years Bacteria 1 hour to 1 day 1,000 hours (42 days) to 2.7 years 8.7 billion to 370.4 million Pets: dog/cat 2 years 2,000 years 500,000 Humans 22 years 22,000 years 45,000 Science, Evolution, and Creationism 

members of the subgroup may no longer respond to court- ship or other signals from members of the original population. Eventually, genetic changes will become so substantial that the members of different subgroups can no longer produce viable offspring even if they do mate. In this way, existing species can continually “bud off” new species. Over very long periods of time, continued instances of speciation can produce organisms that are very different from their ancestors. Though each new species resembles the species from which it arose, a succession of new species can diverge more and more from an ancestral form. This divergence from an ancestral form can be especially dramatic when an evolu- tionary change enables a group of organisms to occupy a new habitat or make use of resources in a novel way. Consider, for example, the continued evolution of the tet- When tetrapods (such rapods after limbed animals began living on land. As new species of plants as this sea turtle laying evolved and covered the Earth, new species of tetrapods appeared with features its eggs on a coastal beach) evolved the abil- that enabled them to take advantage of these new environments. The early tetra- ity to lay hard-shelled pods were amphibians that spent part of their lives on land but continued to lay eggs, they no longer their eggs in the water or in moist environments. The evolution about 340 million had to return to the years ago of amniotic eggs, which have structures such as hard or leathery shells water to reproduce. The last common ances- tor of the four-legged animals living today gave rise to amphibians and was the predeces- sor of reptiles. Birds and mammals evolved from different lineages of ancient reptiles.  Science, Evolution, and Creationism

Evolution in Industry: Putting Natural Selection to Work The concept of natural selection has been applied in many fields outside biology. For example, chemists have applied principles of natural selection to develop new molecules with specific functions. First they create variants of an existing molecule using chemi- cal techniques. They then test the variants for the desired function. The variants that do the best job are used to generate new variants. Repeated rounds of this selection process result in molecules that have a greatly enhanced ability to perform a given task. This technique has been used to create new enzymes that can convert cornstalks and other agricultural wastes into ethanol with increased efficiency. and additional membranes that allow developing embryos to survive in dry environments, was one of the key developments in the evolution of the reptiles. The early reptiles split into several major lineages. One lineage led to reptiles, including dinosaurs, and also to birds. Another lineage gave rise to mammals between 200 million and 250 million years ago. The evolutionary transition from reptiles to mammals is particularly well documented in the fossil record. Successive fossil forms tend to have larger brains and more specialized sense organs, jaws and teeth adapted for more efficient chewing and eating, a gradual movement of the limbs from the sides of the body to under the body, and a female reproductive tract increasingly able to support the internal development and nourishment of young. Many of the biological novelties seen in mammals may be associated with the evolution of warm-bloodedness, which enabled a more active lifestyle over a much larger range of temperatures than in the cold-blooded reptilian ancestors. Then, between 60 million and 80 million years ago, a group of mammals known as the primates first appeared in the fossil record. These mammals had grasping hands and feet, frontally directed eyes, and even larger and more complex brains. This is the lineage from which ancient and then modern humans evolved. Science, Evolution, and Creationism 

Scientists seek explanations of natural phenomena based on empirical evidence. Advances in the understanding of evolution over the past two centuries provide a superb example of how science works. Scientific knowledge and understanding accumulate from the interplay of observation and explanation. Scientists gather information by observing the natural world and conducting experiments. They then propose how the systems being studied behave in general, basing their explanations on the data provided through their experi- ments and other observations. They test their explanations by conducting additional observations and experiments under different conditions. Other scientists confirm the observations independently and carry out additional studies that may lead to more sophisticated explanations and predictions about future observations and experiments. In these ways, scientists continu- ally arrive at more accurate and more comprehensive explanations of particu- lar aspects of nature. In science, explanations must be based on naturally occurring phenomena. Natural causes are, in principle, reproducible and therefore can be checked independently by others. If explanations are based on purported forces that are outside of nature, scientists have no way of either confirming or disprov- ing those explanations. Any scientific explanation has to be testable — there must be possible observational consequences that could support the idea but also ones that could refute it. Unless a proposed explanation is framed in a way that some observational evidence could potentially count against it, that explanation cannot be subjected to scientific testing. Definition of Science The use of evidence to construct testable explanations and predictions of natural phenomena, as well as the knowledge generated through this process. Because observations and explanations build on each other, science is a cumulative activity. Repeatable observations and experiments generate expla- nations that describe nature more accurately and comprehensively, and these explanations in turn suggest new observations and experiments that can be used to test and extend the explanation. In this way, the sophistication and scope of scientific explanations improve over time, as subsequent generations of scientists, often using technological innovations, work to correct, refine, and extend the work done by their predecessors. 10 Science, Evolution, and Creationism

Is Evolution a Theory or a Fact? It is both. But that answer requires looking more vations and experiments that were not possible deeply at the meanings of the words “theory” previously. and “fact.” One of the most useful properties of scientific In everyday usage, “theory” often refers to theories is that they can be used to make predic- a hunch or a speculation. When people say, “I tions about natural events or phenomena that have have a theory about why that happened,” they not yet been observed. For example, the theory of are often drawing a conclusion based on frag- gravitation predicted the behavior of objects on the mentary or inconclusive evidence. Moon and other planets long before the activities The formal scientific definition of theory is of spacecraft and astronauts confirmed them. The quite different from the everyday meaning of evolutionary biologists who discovered Tiktaalik the word. It refers to a comprehensive explana- (see page 2) predicted that they would find fossils tion of some aspect of nature that is supported intermediate between fish and limbed terrestrial by a vast body of evidence. animals in sediments that were about 375 million Many scientific theories are so well estab- years old. Their discovery confirmed the prediction lished that no new evidence is likely to alter made on the basis of evolutionary theory. In turn, them substantially. For example, no new evi- confirmation of a prediction increases confidence in dence will demonstrate that the Earth does that theory. not orbit around the Sun (heliocentric theory), In science, a “fact” typically refers to an obser- or that living things are not made of cells (cell vation, measurement, or other form of evidence theory), that matter is not composed of atoms, that can be expected to occur the same way under or that the surface of the Earth is not divided similar circumstances. However, scientists also use into solid plates that have moved over geologi- the term “fact” to refer to a scientific explanation cal timescales (the theory of plate tectonics). that has been tested and confirmed so many times Like these other foundational scientific theo- that there is no longer a compelling reason to keep ries, the theory of evolution is supported by so testing it or looking for additional examples. In many observations and confirming experiments that respect, the past and continuing occurrence of that scientists are confident that the basic com- evolution is a scientific fact. Because the evidence ponents of the theory will not be overturned supporting it is so strong, scientists no longer ques- by new evidence. However, like all scientific tion whether biological evolution has occurred and theories, the theory of evolution is subject to is continuing to occur. Instead, they investigate the continuing refinement as new areas of science mechanisms of evolution, how rapidly evolution can emerge or as new technologies enable obser- take place, and related questions. In science it is not possible to prove with absolute certainty that a given explanation is complete and final. Some of the explanations advanced by sci- entists turn out to be incorrect when they are tested by further observations or experiments. New instruments may make observations possible that reveal the inadequacy of an existing explanation. New ideas can lead to explana- tions that reveal the incompleteness or deficiencies of previous explanations. Many scientific ideas that once were accepted are now known to be inaccurate or to apply only within a limited domain. Science, Evolution, and Creationism 11

However, many scientific explanations have been so thoroughly tested that they are very unlikely to change in substantial ways as new observations are made or new experiments are analyzed. These explanations are accepted by scientists as being true and factual descriptions of the natural world. The atomic structure of matter, the genetic basis of heredity, the circulation of blood, gravitation and planetary motion, and the process of biological evolution by natural selection are just a few examples of a very large number of scientific explanations that have been overwhelmingly substantiated. Science is not the only way of knowing and understanding. But science is a way of knowing that differs from other ways in its dependence on empirical evidence and testable explanations. Because biological evolution accounts for events that are also central concerns of religion — including the origins of biological diversity and especially the origins of humans — evolution has been a conten- tious idea within society since it was first articulated by Charles Darwin and Alfred Russel Wallace in 1858. Acceptance of the evidence for evolution can be compatible with religious faith. Today, many religious denominations accept that biological evolution has produced the diversity of living things over billions of years of Earth’s his- tory. Many have issued statements observing that evolution and the tenets of their faiths are compatible. Scientists and theologians have written eloquently about their awe and wonder at the history of the universe and of life on this planet, explaining that they see no conflict between their faith in God and the evidence for evolution. Religious denominations that do not accept the occur- rence of evolution tend to be those that believe in strictly literal interpretations of religious texts. Science and religion are based on different aspects of human experience. In science, explanations must be based on evidence drawn from examining the natural world. Scientifically based observations or experiments that conflict with an explanation eventually must lead to modification or even abandon- ment of that explanation. Religious faith, in contrast, does not depend only on empirical evidence, is not necessarily modified in the face of conflicting evidence, and typically involves supernatural forces or entities. Because they are not a part of nature, supernatural entities cannot be investigated by sci- ence. In this sense, science and religion are separate and address aspects of human understanding in different ways. Attempts to pit science and religion against each other create controversy where none needs to exist. 12 Science, Evolution, and Creationism

Excerpts of Statements by Religious Leaders Who See No Conflict Between Their Faith and Science Many religious denominations and individual religious leaders have issued statements acknowledging the occurrence of evolution and pointing out that evolution and faith do not conflict. “[T]here is no contradiction between an evolutionary theory of human origins and the doctrine of God as Creator.” “[S]tudents’ ignorance about evolution will seriously undermine their understanding — General Assembly of the Presbyterian Church of the world and the natural laws gov- erning it, and their introduction to other explanations described as ‘scientific’ will give them false ideas about scientific methods and criteria.” — Central Conference of American Rabbis “In his encyclical Humani Generis (1950), my predecessor Pius XII has already affirmed that there is no conflict between evolution and the doctrine of the faith regarding man and his vocation, provided that we do not lose sight of certain fixed points. . . . Today, more than a half-century after the appearance of that encyclical, some new findings lead us toward the recognition of evolution as more than an hypothesis. In fact it is remarkable that this theory has had progressively greater influence on the spirit of researchers, following a series of discoveries in different scholarly disciplines. The convergence in the results of these independent studies — which was neither planned nor sought — constitutes in itself a signifi- cant argument in favor of the theory.” — Pope John Paul II, Message to the Pontifical Academy of Sciences, October 22, 1996. Science, Evolution, and Creationism 13

E. O. Wilson’s Theory of Everything

At 82, the famed biologist E. O. Wilson arrived in Mozambique last summer with a modest agenda—save a ravaged park identify its many undiscovered species create a virtual textbook that will revolutionize the teaching of biology. Wilson’s newest theory is more ambitious still. It could transform our understanding of human nature—and provide hope for our stewardship of the planet.

M y first glimpse of E. O. Wilson came in July, in the late afternoon, when the light fades and dies with alarming speed in Mozambique. He had emerged from his cabin within Gorongosa National Park, one of southern Africa’s great, historic game reserves, just as the nightly winter chill was bestirring itself, and across an expanse of garden, he appeared almost spectral: tall, gaunt, white-haired, and possessed of a strange gait—slow and deliberate, yet almost woozy in the faint swerve described by each long-legged stride.

Wilson’s head was cocked sharply downward as he walked, as if he suffered a neck condition. (Later he would tell me this habit grew from a lifetime of scanning the ground for insect life.) In his right hand, he carried a flowing white net, like what Vladimir Nabokov might have used to pursue butterflies by Lake Geneva. Without fanfare, just before dark, on the first evening of his first visit to Africa below the Sahara, he had begun his first bug-collecting expedition.

If one had to give E. O. Wilson a single label, evolutionary biologist would be as good as any. Sociobiologist, lifelong naturalist, prolific author, committed educator, and high-profile public intellectual might all also serve. But amidst his astonishing range and volume of intellectual output, Wilson’s reputation, and most of his big ideas, have been founded primarily on his study of ants, most famously his discoveries involving ant communication and the social organization of ant communities. As I caught up with him, intending to introduce myself, he stooped down low toward the garden’s dirt path to pick one up, pronouncing its scientific name with the raw delight of a boy hobbyist, and exclaiming, “I think I’ll keep that one. Let me go get a vial and some alcohol to put it in.”

Many more collecting forays would follow over the next two weeks, most of them more concerted than this. But other motives had also lured Wilson, age 82, so far from his home in Lexington, Massachusetts. It is hard to order such things with any precision, so varied and intertwined are Wilson’s interests, but the principal attractions, he told me, involved the chance to explore a rare and imperiled African ecosystem—one largely cut off from scientific study until late last year—and to play an advisory role in its conservation. What made this park, at the southern extremity of Africa’s Great Rift Valley, of particular interest to him was the chance to revisit a field that he helped invent—biogeography, and specifically the special ecology and biodiversity of islands.

Gorongosa’s heavily wooded mountain of the same name was effectively incorporated into the park, by national decree, only last December. It is home to the only largely intact rain forest in all of Mozambique, a semitropical country roughly the size of Texas and Oklahoma. Solitary and broad-shouldered, the mountain rises more than 6,000 feet above the surrounding plains, providing a local climate unlike any other for hundreds of miles around it. It draws its water from the warm, moist winds that blow in from the nearby Indian Ocean, kissing its cool upper flanks and sustaining a unique ecosystem of rare orchids, mountain cypress, and rich bird life like the green-headed oriole, along with any number of other species yet to be identified.

For many years, the religious taboos of local residents kept the mountain from being opened to scientists and tourists, and also offered some measure of environmental protection. Nonetheless, a helicopter ride I recently took revealed the mountain to be under steady attack by locals setting fires to clear fields for farming and to smoke out wild edibles, from bushmeat to insect delicacies. Time and again, Wilson has come back to the subject of ecological hot spots like this in his writing. More than half of the planet’s plant and animal species live in tropical rain forests, which occupy a mere 6 percent of the world’s land surface—territory roughly the size of the lower 48 American states. Across these unique havens of biodiversity, Wilson has estimated that an area equivalent to half the state of Florida is being destroyed each year.

Wilson described Mount Gorongosa’s rain forest to me as “an island in a sea of grasslands,” and said that “biologists should be straining to get there,” to study it and to save it, just as they would some new reef system discovered in an underexplored part of the Pacific. Of the need to thoroughly survey places like Gorongosa, he wrote in his 1984 book, Biophilia: “No process being addressed by modern science is more complicated or, in my opinion, more important.”

Wilson’s first book, The Theory of Island Biogeography, published in 1967, became one of the most influential works in ecological studies. It offered a formula that mathematically predicts a geometric reduction in the biodiversity of a given habitat as the size of the habitat shrinks. Part of Wilson’s work at Gorongosa involved launching a survey of life on the mountain, and also seeking to understand the special dynamics of a park that is small by the standards of its continent, but that nonetheless may contain thousands of species never before discovered, many of them unique to this lonely peak.

Throughout Wilson’s stay here, a team of filmmakers, whose presence attested to a different purpose, trailed him from day to day. Together, Wilson and the filmmakers have selected the park as one of the backdrops for an online, interactive digital textbook called Life on Earth that the Harvard professor emeritus hopes will revolutionize the teaching of biology in secondary schools worldwide.

For all of his projects here, Wilson has a benefactor whose enthusiasm runs as deep as his pockets: Greg Carr, a boyish 51-year-old who grew up in Idaho Falls and made a fortune in the 1980s and ’90s by developing corporate voice-mail systems. Since then, Carr has undertaken a variety of philanthropic activities, including the endowment of a human-rights center at Harvard that bears his name. But in recent years he has made the rehabilitation of Gorongosa Park his personal mission. Since he assumed joint operational control of the park in 2004, in partnership with the Mozambique government, Carr has spent, by his own estimate, perhaps $25 million on the park.

In its heyday in the early 1970s, the park, with its savannas and floodplains, provided one of the richest nature- and game-viewing experiences anywhere in Africa, due particularly to the abundance of its so-called charismatic animals—lions, cheetahs, leopards, elephants, wildebeests, zebras, and more. Back then, it was said that one day spent in Gorongosa was equivalent to three in South Africa’s larger and more famous Kruger National Park. In 1977, however, a rebel movement named Renamo launched a civil war from headquarters in Gorongosa, and things went calamitously downhill.

Nearly a million Mozambicans died as a result of the war, and five times that many people were displaced. “Basically every day, there was fighting in this area, and soldiers slaughtered the animals for food, while ordinary people hunted them because it was impossible to farm,” said Domingos João Muala, a Mozambican park worker and ethnologist. This led to the wholesale elimination of both large grazing mammals and their predators, although I chanced on a pride of lions, rare within the park today, on one cold morning as we emerged from a Land Rover by the ruins of an old park lodge fittingly known as the Lion House.

Mozambique’s civil war came to a negotiated end in 1992, and multiparty elections followed two years later. Rehabilitation work on the park began in 1994, including the hiring of staff and the reopening of roads. Poaching has been gradually suppressed but remains a problem even now. Carr’s ambition is to restore as much of the original ecosystem as possible, all the way up to the apex predators, like cheetahs, four of which his foundation recently acquired for release onto park plains already teeming again with antelope, warthog, and baboon.

Wilson’s faith in the power of conservation movements to restore and preserve places like Gorongosa waxed and waned during the week I spent with him. He talked about the impact of China’s burgeoning appetite for natural resources from Africa, and worried about Africa’s booming population, which is projected to go from roughly 1 billion today to twice that by mid-century. And he offered a dark caution about global warming and the unpredictable impact it will have on many ecosystems, no matter how carefully we try to protect them.

Yet these moments of pessimism gradually came to be overshadowed by an abiding optimism, which seemed to grow stronger as he articulated what he saw as a workable vision of this region’s future. “When I flew in by helicopter, one of the things that impressed me the most was the agriculture,” he said. “Those people are really using the poorest methods to eke out a living, and very little technology. Well, it wouldn’t take all that much to change this. With the introduction of fertilizers and better irrigation and more machinery, the yields could go up pretty quickly, and so would people’s incomes. And with that, what you would see is people moving to cities, and new cities forming, which is the way to relieve pressure on the land. It should be noted that presently, Africa is the world’s fastest-urbanizing continent.”

In many of his writings, Wilson places hope in arguments that range from the ethical (humankind will ultimately awaken to its responsibility to the Earth), to the genetic (our evolutionary background has conditioned us to yearn for such things as unspoiled savannas and wilderness), and finally to a kind of naturalist’s spiritualism. “For the naturalist, every entrance into a wild environment rekindles an excitement that is childlike in spontaneity, [and] often tinged with apprehension,” he wrote in his 2002 book, The Future of Life. Every such experience, he continued, reminds us of “the way life ought to be lived, all the time.”

Over dinner on Wilson’s first night at Gorongosa, Carr asked whether the park stood any chance of still retaining all the species it now contains when his young niece reaches her 90s. Wilson’s answer was an exuberant “Yes!” Eventually, the conversation between the biologist and the billionaire turned to the possibility of dramatically expanding the park to create a protected corridor all the way to the Indian Ocean. It was an idea whose logic flows directly from the precepts of island biogeography, which show a dramatic correlation between the size of a habitat and both its diversity and its sustainability. “I see no reason why not,” Wilson enthused. “By all means, you should do it!”

C onversations like these might give the impression that Wilson—one of the most driven and prolific biologists of his generation—has mellowed and is shifting now to a quieter, more retiring, if not truly retired, phase of life, settling into the easy-fitting robes of scientific eminence and mostly lending endorsements and encouragement to the good works of others. And his bug collecting could easily be misinterpreted as a mere enthusiasm, a nostalgic return to the field. But Wilson had rebuked me in our very first encounter, after he had picked up the ant for close inspection, pointedly declaring that he was interested in “more than ants,” and his travel here, like almost everything he does, is bound up with ideas and themes that he has doggedly pursued for decades. (Even in his recently published first novel, the best-selling Anthill, his 24th book, readers schooled in evolutionary science cannot miss the play of long-gestating Wilsonian theories, and linkages to his latest work.)

Indeed, while we sat in camp chairs talking about conservation and ants and countless other subjects, a dispute was raging among evolutionary biologists half a world away, one of the most hotly contested in that field in years—and Wilson was at its center. Christopher X J. Jensen, a Pratt Institute biologist who has blogged about the conflict, described it as a “scientific gang fight.” Its outcome could have big implications for how we understand ourselves and our motivations—and particularly the complex interplay of selfish and altruistic behavior in human nature.

This is hardly the first scientific controversy surrounding Wilson. An even bigger fight erupted around him in the 1970s, as he laid out his ideas on sociobiology in three landmark books, The Insect Societies, Sociobiology, and On Human Nature. At issue throughout were his claims that our genes not only are responsible for our biological form, but help shape our instincts, including our social nature and many other individual traits.

These contentions drew fierce criticism from all across the social sciences, and from prominent specialists in evolution such as Wilson’s late Harvard colleague, Stephen Jay Gould, who helped lead the charge against him.

Wilson defined sociobiology for me as “the systematic study of the biological basis of all forms of social behavior in all organisms.” Gould savagely mocked both Wilson’s ideas and his supposed hubris in a 1986 essay titled “Cardboard Darwinism,” in The New York Review of Books, for seeking “to achieve the greatest reform in human thinking about human nature since Freud,” and Wilson still clearly bears a grudge.

“I believe Gould was a charlatan,” he told me. “I believe that he was … seeking reputation and credibility as a scientist and writer, and he did it consistently by distorting what other scientists were saying and devising arguments based upon that distortion.” It is easy to imagine Wilson privately resenting Gould for another reason, as well—namely, for choosing Freud as a point of comparison rather than his own idol, Darwin, whom he calls “the greatest man in the world.”

“Darwin is the one who changed everything, our self-conception greater than Copernicus,” Wilson told me. “This guy is irritatingly correct, time and time again, even when he has limited evidence.” In Darwin’s mold, the thrust of Wilson’s life work has been aimed at changing humankind’s self-conception. Indeed it can be difficult, from today’s vantage point, to see what much of the fuss of the 1970s was about, so thoroughly has the Wilsonian idea that our genes shape our nature penetrated the mainstream.

This reality is illustrated, among countless possible examples, in Francis Fukuyama’s most recent book, The Origins of Political Order: From Prehuman Times to the French Revolution. Rejecting the views of classic political philosophers like Hobbes, Locke, and Rousseau that primitive humankind started out as a collection of scattered, unorganized individuals, Fukuyama writes: “Human sociability is not a historical or cultural acquisition, but something hardwired into human nature.” Nowhere is Wilson, who pioneered this view, even mentioned.

The current controversy results from another bid by Wilson to overturn conventional scientific wisdom. For more than four decades, evolutionary biology has been dominated by a school of thought known as “kin selection,” which postulates that some species arrive at cooperative behavior and a complex division of labor as a matter of reproductive strategy among close relatives. In other words, self-sacrifice and other forms of altruism are really driven by what might be described as a coolly selfish calculation: cooperation among related individuals favors the reproduction of kin and hence the propagation of shared genes. This notion was established in a famous mathematical rule laid out by W. D. Hamilton in 1964, Rb>c, which means that genetic benefits (b) realized by helping a relative (R) pass on his or her genes must be greater than the cost (c) of assisting that relative in order for the behavior to be favored by natural selection.

Wilson believes that this whole theory has been a wrong turn, intellectually, and that this bedrock concept, with major implications for understanding our own nature, is overdue for radical revision.

The furor erupted with the publication, in the scientific journal Nature in August 2010, of an article written by Wilson and two co-authors, Martin A. Nowak and Corina E. Tarnita, both of Harvard. Titled “The Evolution of Eusociality,” it amounted to a frontal challenge to a key concept of kin-selection theory, called “inclusive fitness.” Among other things, inclusive fitness says that species like ants have become highly social, and that the sisters that make up the overwhelming bulk of any colony cede the right to reproduce to the queen, because of the extraordinarily high degree of genetic relatedness between the sisters, which surpasses even that between mother and daughter.

Ants and humans are among the very few “eusocial” animals—the most highly social creatures in the history of life on Earth, capable of building complex societies in which individuals specialize in various activities and sometimes act altruistically. Darwin himself, in his most influential book, The Origin of Species, recognized the vexing question of why female ants would sacrifice the right to reproduce rather than seek to pass along their own genes as the greatest challenge to his theory of evolution. Now, employing advanced mathematics involving evolutionary game theory and population genetics, the authors of the controversial Nature article have shaken up the evolutionary-biology establishment by rejecting kin selection, and claiming that the close genetic similarity of sister ants is not mathematically necessary to explain their “eusociality”—and, indeed, is not the cause of it.

The mathematical heavy lifting comes from Nowak and Tarnita, showing, in the words of Nowak, that “simple versions of Hamilton’s rule … are almost always wrong,” and that recent efforts to create more-generalized versions of the rule are of no help in explaining evolution. But the proposed new interpretation of what causes ants and a few other species to become highly social, to the point of intricate specialization and even self-sacrifice, or altruism, is classic Wilson. “The causative agent,” the authors wrote, “is the advantage of a defensible nest.” Eusocial creatures are driven to cooperate not by their relatedness, in other words, but by the advantages that accrue to any group from the division of labor. As natural circumstance forced individuals to interact, certain cooperative traits became advantageous, and proliferated, in a handful of cases.

In support of their attack on kin selection, the authors invoke the rarity of eusociality across the animal kingdom, even among species in which the genetic similarity of kin is extremely high. Among species that use clonal reproduction, for example, only one major group, the gall-making aphids, are known to be eusocial. What’s more, eusocial behavior can occur—even among insects—in the absence of kinship. One example is the propensity of certain solitary bees to behave like eusocial bees when they are forced to live together in the laboratory. “The coerced partners proceed variously to divide labor in foraging, tunneling, guarding.”

The authors conclude that a very small number of species simply seem to be genetically “spring-loaded,” or “strongly predisposed” to the development of eusociality in conditions where natural selection favors it. The article then ropes humans into the picture in its last and most provocative sentence: “We have not addressed the evolution of human social behavior here, but parallels with the scenarios of animal eusocial evolution exist, and they are, we believe, well worth examining.” Until now, the conventional wisdom on the social evolution of humans has focused on the growth and development of the brain, not on the existence of a social gene or set of such genes that may have spring-loaded humans for civilization—or for altruism. Yet Wilson and his co-authors imply that such genes very likely exist.

The outcry from the evolutionary-theory establishment, including luminaries in the field ranging from Richard Dawkins to Robert Trivers, was exceptionally fierce, including unusually personal attacks. One of several critical letters to the editor published by Nature was signed by 137 scientists. Another letter called the authors’ findings “largely irrelevant.”

Elsewhere, commentators objected that Nature should never have published the article, and only did so because Wilson’s name was attached to it. Some claimed that the authors had not fully understood or had willfully misrepresented kin-selection theory. One commentator even wrote off Wilson for his “senescence.” On his blog, Jerry A. Coyne, a leading figure in the field and a professor in the department of ecology and evolution at the University of Chicago, voiced pity for Tarnita, a Romanian theoretical mathematician who works at Harvard’s Program for Evolutionary Dynamics. Calling the paper “dreck,” he said that it “will always cast a shadow over her career.”

“Nowak et al.,” as the authors are called in the Nature back-and-forth, have firmly held their ground. “Inclusive fitness theory,” they wrote in their published response, “is neither useful nor necessary to explain the evolution of eusociality or other phenomena.” In an e-mail to me, Tarnita wrote about the criticisms directed at her:

In collaborating with Nowak and Tarnita, Wilson was in effect reprising a tactic that led to his first major theoretical triumph, with island biogeography—joining forces with talented mathematicians. In that instance, in the early 1960s, he teamed up with the late Robert H. MacArthur, whose work on population growth and competition, Wilson says, made him the most important ecologist of his generation.

“Nothing is more attractive to me than a muddled domain awaiting its first theory,” Wilson wrote in Biophilia:

W ilson told me the new proposed evolutionary model pulls the field “out of the fever swamp of kin selection,” and he confidently predicted a coming paradigm shift that would promote genetic research to identify the “trigger” genes that have enabled a tiny number of cases, such as the ant family, to achieve complex forms of cooperation. His next book, The Social Conquest of Earth, expands on his theories—and takes up the question left dangling at the end of the Nature article. “It starts with posing the questions that I call the most fundamental of philosophy and religion,” he said. “Where did we come from, what are we, and where are we going?”

Wilson explained the book, which will be released in April, during an animated two-hour discussion on a day that he’d previously set aside for rest. Earlier that morning, he had turned up in his usual baggy, sagging khaki pants and installed himself at a table outside the Gorongosa camp restaurant, slumping silently into a flimsy plastic chair. Soon he could be seen jotting ideas in his small, neat hand, on a yellow legal pad. Once in a while he would tear off a sheet, number it, fold it carefully, and put it in the side pocket of the same blue-striped sport coat he wore every day.

Later he told me that he’s done all of his writing that way, relying on Kathleen M. Horton, the assistant who has worked with him for 45 years, to enter material into a computer and help edit his writing. “Most people are now aware that the digital age is upon us,” he said, with a twinkle in his left eye, the other sightless from a boyhood accident. “It has left me behind. I haven’t had time to learn iPhones and tablets, or even how to run a computer properly, but it’s arrived.”

Wilson told me he’d worked for a decade on the ideas he presents in Social Conquest, drawing on the primary literature in a wide variety of fields to refine his views. These ranged, he said, from molecular genetics and ecology to anthropology and cognitive science. In the book, he proposes a theory to answer what he calls “the great unsolved problem of biology,” namely how roughly two dozen known examples in the history of life—humans, wasps, termites, platypodid ambrosia beetles, bathyergid mole rats, gall-making aphids, one type of snapping shrimp, and others—made the breakthrough to life in highly social, complex societies. Eusocial species, Wilson noted, are by far “the most successful species in the history of life.” Humankind, of course, has thoroughly transformed the environment, achieving a unique dominion. And ants, by some measures, are more successful still. (If you were to weigh all the animals on the planet, you would find that the mass of ants exceeds that of all other insects combined, and also that of all terrestrial nonhuman vertebrates.)

“Wow, the butterflies are out,” Wilson interjected mid-sentence, as a pretty, modestly sized, yellow-and-black creature floated dizzily around his chair.

Wilson announced that his new book may be his last. It is not limited to the discussion of evolutionary biology, but ranges provocatively through the humanities, as well. Summarizing parts of it for me, Wilson was particularly unsparing of organized religion, likening the Book of Revelation, for example, to the ranting of “a paranoid schizophrenic who was allowed to write down everything that came to him.” Toward philosophy, he was only slightly kinder. Generation after generation of students have suffered trying to “puzzle out” what great thinkers like Socrates, Plato, and Descartes had to say on the great questions of man’s nature, Wilson said, but this was of little use, because philosophy has been based on “failed models of the brain.”

Answers to the fundamental mysteries of human nature can only be found elsewhere, Wilson told me—in science, and most particularly in genetics and evolution.

Wilson had begun this particular conversation promising to answer the question of what caused the shift from the genus Australopithecus to Homo and led to the line that ultimately became human. But now he asked, “Can we have lunch before I tell you?,” clearly enjoying playing up the drama.

His theory draws upon many of the most prominent views of how humans emerged. These range from our evolution of the ability to run long distances to our development of the earliest weapons, which involved the improvement of hand-eye coordination. Dramatic climate change in Africa over the course of a few tens of thousands of years also may have forced Australopithecus and Homo to adapt rapidly. And over roughly the same span, humans became cooperative hunters and serious meat eaters, vastly enriching our diet and favoring the development of more-robust brains.

By themselves, Wilson says, none of these theories is satisfying. Taken together, though, all of these factors pushed our immediate prehuman ancestors toward what he called a huge pre-adaptive step: the formation of the earliest communities around fixed camps.

“When humans started having a camp—and we know that Homo erectus had campsites—then we know they were heading somewhere,” he told me. “They were a group progressively provisioned, sending out some individuals to hunt and some individuals to stay back and guard the valuable campsite. They were no longer just wandering through territory, emitting calls. They were on long-term campsites, maybe changing from time to time, but they had come together. They began to read intentions in each other’s behavior, what each other are doing. They started to learn social connections more solidly.”

Wilson’s “campsite” theory, of course, connects us directly back to the species described in the Nature article, and helps him lump humans together with the handful of other known species to have made it across what he calls the evolutionary “bottleneck” toward highly structured social life. “The humans become consistent with all the others,” he said, and the evolutionary steps were likely similar—beginning with the formation of groups within a freely mixing population, followed by the accumulation of pre-adaptations that make eusociality more likely, such as the invention of campsites. Finally comes the rise to prevalence of eusocial alleles—one of two or more alternative forms of a gene that arise by mutation, and are found at the same place on a chromosome—which promote novel behaviors (like communal child care) or suppress old, asocial traits. Now it is up to geneticists, he adds, to “determine how many genes are involved in crossing the eusociality threshold, and to go find those genes.”

But the story does not end here. In his new book, Wilson posits that two rival forces drive human behavior: group selection and what he calls “individual selection”—competition at the level of the individual to pass along one’s genes—with both operating simultaneously. “Group selection,” he said, “brings about virtue, and—this is an oversimplification, but—individual selection, which is competing with it, creates sin. That, in a nutshell, is an explanation of the human condition.

“Our quarrelsomeness, our intense concentration on groups and on rivalries, down to the last junior-soccer-league game, the whole thing falls into place, in my opinion. Theories of kin selection didn’t do the job at all, but now I think we are close to making sense out of what human beings do and why they can’t settle down.”

By settling down, Wilson said, he meant establishing a lasting peace with each other and learning to live in a sustainable balance with the environment. If Wilson’s new paradigm holds up—“and it will,” he insisted in an e-mail exchange several weeks after visiting Gorongosa—its impact on the social sciences could be as great as its importance for biology, advancing human self-understanding in ways typically associated with the great philosophers he criticized.

“Within groups, the selfish are more likely to succeed,” Wilson told me in a telephone conversation. “But in competition between groups, groups of altruists are more likely to succeed. In addition, it is clear that groups of humans proselytize other groups and accept them as allies, and that that tendency is much favored by group selection.” Taking in newcomers and forming alliances had become a fundamental human trait, he added, because “it is a good way to win.”

Kin-selection theory would explain nepotism, but not the more complex rivalries and alliances that we see throughout human history. If Wilson is right, the human impulse toward racism and tribalism could come to be seen as a reflection of our genetic nature as much as anything else—but so could the human capacity for altruism, and for coalition- and alliance-building. These latter possibilities may help explain Wilson’s abiding optimism—about the environment and many other matters. If these traits are indeed deeply written into our genetic codes, we might hope that we can find ways to emphasize and reinforce them, to build problem-solving coalitions that can endure, and to identify with progressively larger and more-inclusive groups over time.

Once the book comes out, Wilson said, he expects parts of the biological mainstream to howl on cue. He is just as certain, though, that there will be many converts. “I am going to get fuselaged—you know, bombarded,” he said, laughing. “I don’t care, though, because I feel so secure about the theory and interpretation.”

I n Gorongosa, Wilson’s study of complex social behavior was centered on the termite, an insect that seemed to obsess him at times during his stay. Termites are unrelated to ants rather, they are distant cousins of cockroaches. As such, their reproductive strategy is entirely dissimilar to that of ants. But like ants, they are on the shortlist of eusocial animals. For Wilson, how such different creatures ended up creating highly structured societies, replete with castes and the complex division of labor, remains a source of fascination and ongoing study.

Nonetheless, during much of his stay, termite research was crowded out by the broader conservation effort that had brought him here, and by the Life on Earth project—and indeed, the two often ran together, as film crews shadowed him, recording material for the textbook.

One morning, I traveled with him to Mount Gorongosa for an event billed as a “bio blitz,” which combined a classic natural-history specimen-gathering exercise, textbook-filming, and an educational opportunity for the scores of village children who were enlisted in the effort. Normally events like these bring together a diverse team of biologists, but Wilson, who was seated at a table in a makeshift shelter beside a clear stream and just above a waterfall, was on his own this time, and clearly relished being the center of the action.

“You will be seen by other students in many places,” he explained through a translator, as video crews filmed. “Because we wish to help science, we wish to know what is all around here, what species exist here. It is good for your education to see how studies in science can be done, how you can do studies in science.”

Ziploc-style bags were passed out, and Wilson told the children, who sat on the ground before him, to collect all the “creatures, little animals, insects, spiders” they could find, and bring them to him for identification. With that, the children, let loose on the mountainside, threw themselves into the task with abandon, tromping through the stream, seizing bugs in the tall grass, and pursuing other creatures up the hillsides.

As the bagged bugs, lizards, scorpions, and other creatures they brought forth began to pile high, Wilson became almost giddy, seemingly reliving the thrills of his Alabama childhood, when his avid specimen-hunting fostered a growing fascination with nature, and eventually a love of science. For minutes at a time, the white-haired scientist resembled nothing so much as a grandmaster smiting a score of enthusiastic challengers at a speed-chess exhibition, as he quickly named each animal brought to him:

“And here we have—very good—a lycaenid butterfly. Probably that’s a new species, but I’m not going to keep it. Who got that butterfly? … What is this? Wait a minute, where is my magnifying glass, I’ll tell you. Oh yeah, that one I know. I know the genus. That one is a Tetragnatha. … Now the ants … This is an important one. Can you be sure to get that one? All right, wait a minute. I want that one. It’s different. That’s a reduviid, an assassin bug … That’s a—wait a minute, it’ll come to me. This is a coccinellid.”

This medley, one of many, concluded with Wilson saying: “Wow, this is the way to make a real collection, if you are an entomologist. Get a bunch of kids around. No, seriously.”

Later, in a quieter moment, I asked Wilson how he managed to name so many of the creatures, particularly ones far outside his specialty, and on a continent he’s never visited before. He told me that he’d prepped intensively for the experience for two months, consulting both reference books and experts, committing the descriptions of thousands of species to memory. Silently, I recalled a critic’s recent characterization of him as senescent.

A few days earlier, Wilson, remarkably, had taken his very first helicopter ride, a shuttle run that brought him from the nearby port city of Beira to the park’s immense floodplain, dotted by riverine pools thick with caucusing hippos and crocodiles, and finally to a close view of the mountain itself. “Mount Gorongosa!” he exclaimed to me later. “It has always loomed in my imagination as this dark, brooding mountain, but boy, is it magnificent so bright, so full of life!”

With that, I asked Wilson what made this place so special for him. “Every place is special,” he answered. “But this is—even among all the varieties of natural history that you can get in parks around the world—this one stands out because of its tragic history. The destruction that is being healed, largely through the efforts of one man, this Greg Carr, showing what can be done.”

After a few days here, Wilson amended his vow not to write more books, saying he would like to return next year to work on a book about Gorongosa and its mountain, tentatively titled Gorongosa: The Park as a Window on Eternity. In lieu of producing any more big, theoretical works, though, Wilson tells me, he longs to spend more of his time traveling. Soon, he said, he plans to go to Yosemite National Park to study a rare ant, and late this year he is planning a seven-week expedition in New Caledonia and Vanuatu. He wants to relive his exploits as a 25-year-old naturalist, when he explored the region as part of a 10-year stint of fieldwork during which he worked out the classification of hundreds of species of ants throughout the Pacific region and elsewhere. “These are the things I want to do—travel, visit the places I’ve wanted to go,” he says.

In such a full life, I asked him how he made sense of his own achievements. “How successful you are depends on a small number of qualities and activities, and one of them is luck,” he answered, laughing. Then the man who had told me, a few days earlier, that he was interested in more than ants confided that he was lucky to have settled on them at a young age.

“For every organism, there exists a problem, for the solution of which that organism is ideally suited,” Wilson said. We had been talking over lunch for about two hours, and Wilson had barely touched his food. He paused for a moment, taking a bite of chicken. “A lot of my work was done with pheromones then came island biogeography, because I could collect enough ants in a short enough period of time to get an idea of the nature of fauna on different islands.” Only then “came the question, ‘What are the driving forces of evolution?’” He put down his fork, and gave a slight smile. “Ants are always there, and this has given me an edge,” he said. “I’ve ridden ants the whole way.”