When you hear the word "evolution" does "neotony" come to mind?

How many ways can we make a home?  I remember as a child walking through the corridors of the American Museum of Natural History and gawking at the many dioramas which combined realistic painting with artifacts or copies of natural and prehistoric settings.  I saw homes of our ancestors built from mammoth tusks in Siberia.  I saw tepees with animal skin wrapped around a cone of trimmed saplings.  I saw igloos built from blocks of ice or compact snow.  Outside the museum I saw the swank apartments of those who lived on Central Park West and imagined the view of Central Park they enjoyed.  I contrasted that with our own Brooklyn cold water flat with a coal stove in the kitchen.  In books I saw castles and mansions that housed the privileged and log cabins that Presidential candidates promoted as their identification with the underprivileged voter or common man.

 

In a similar way there are many mechanisms by which evolution occurs.  There is natural selection in which adaptive traits survive, thus providing the genetic basis for them that enters a new generation and this in turn changes the gene frequency of the population.  There is the “founder effect” in which a small number of individuals enter a new niche and reproduces rapidly in large numbers to create a population that differs in appearance from its original source.  There are hybrids that undergo a doubling of chromosome number and thus establish a new self-reproducing species. There are developmental mutations that can multiply body parts or organs like wings, limbs, or eyes.  There are other developmental mutations that place organs in different parts of the body producing new variations in a species.  One of my favorites is a process called neotony in which juvenile or embryonic features are carried into adult stages.  In the 1920s such neotonous species were found in salamanders in caves, the fertile adults sporting gills which are normally absorbed in the related species living outside the caves. 

We humans have a neotonous origin from out primate ancestors because we have prolonged child-raising period compared to other primates which are sexually mature and functionally adult in fewer years.  The most recently studied neotonous organisms are the birds that had a dinosaur-like ancestry.  They miniaturized as they shifted from living on land to living in trees and then to the skies as they developed wings for flight.  Their eyes are larger (like an embryo’s) in proportion to their bodies.  We do not reflect as much as we should on these neotonous traits in the evolutionary process, and most of the debates about Creationism and Intelligent design are waged over natural selection which is only one of many ways evolution works. 

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MITOCHONDRIAL EVE

Our cells, we have several trillion of them, each contain a nucleus with chromosomes and a surrounding blob of cytoplasm that contains organelles. Organelles do the work of the cell and each type is specialized. One of these is your mitochondria. They are unusual in many ways. They look like bacteria (prokaryotes) and some biologists believe they evolved from bacteria inside other bacteria some three billion years ago. They are usually taught to high school students as being “the powerhouse of the cell.” The phrase means mitochondria take the oxygen we breathe, burn up the food we eat, and give our cells the energy they need to tear apart or synthesize molecules.

Their origin from bacteria makes sense because mitochondria have their own DNA (genes) but the proteins that make up mitochondria come from both our nuclear genes and our mitochondria genes. We get our mitochondria only from our mothers. Our father’s sperm does not contribute any mitochondria to us. Geneticists call such a pattern “maternal inheritance.” The closest thing to it in our culture is Jewishness, which is passed from mother to child; which is why Jews consider the children of an interfaith marriage of a Jewish woman with a non-Jewish male Jewish but the children of a Jewish male with a non-Jewish female are not Jewish (unless they convert to Judaism).

Several years ago when the techniques for sequencing genes into their DNA nucleotides became possible, scientists sampled mitochondria from people in different continents. They compared the sequences and looked for mutant variations. About one such new variant shows up every 250,000 years. If an entire population has that variant it was brought in by a settler, a woman who is ancestral to all those alive today in that ethnic group. If the variant is present in only some of the people of an ethnic group, it arose much later. By comparing the variants around the world, the scientists believed they could identify the mother of us all, dubbed “mitochondrial Eve.” She came from Africa and she lived about 250,000 years ago. Other scientists are not as convinced that the story is this clear. All agree however, that mitochondrial Eve was not the first woman, just a woman who is our Ur-grandmother. All of her kin in Africa (perhaps in the hundreds of thousands or millions) did not end up contributing to our mitochondria.

What this implies is an African origin of our species (Homo sapiens) and the departure from there of our species some quarter of a million years ago to the Middle East, Europe, and Asia and onwards across the Pacific and over Alaska into the New World. Those of you reading this, unless you are of native American descent, are of more recent immigrant settlers to the New World.

No doubt molecular anthropologists will have better and larger samples to check out this hypothesis. Other supporting evidence makes it likely. When I visited Kenya a few years ago, after teaching my students on board the SS Universe about mitochondrial Eve, I mentally paid homage to that remarkable mother of five billion descendants.

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THE NEANDERTAL GENOME AND OUR HUMAN ANCESTRY


At the 74th annual symposium held at Cold Spring Harbor Laboratory, Svante Pääbo presented a paper on the Neandertal genome. Pääbo is a pioneer in extracting ancient DNA and sequencing it. The Neandertals were a species that lived about 400,000 to 30,000 years ago when they went extinct. Pääbo used 75 bones from specimens found in Europe and the Middle East and found that only the more recent bones (30,000 to 40,000 years old) had enough DNA in them to amplify and give fragments large enough to sequence. The average size of the fragments he used was about 50 nucleotide pairs in length. By then matching these through computerized matching, he was able to show that they were similar to our own Homo sapiens sequences from our completed genome. That match-up also showed he had covered 60 percent of the Neandertal genome. He hopes to have a nearly complete genome as he analyzes additional Neandertal bones.

There are lots of problems doing this kind of analysis. Of the DNA he extracts only 3.5% is primate DNA. The rest is bacterial or fungal. The Neandertal genes differ from Homo sapiens genes by about 12.8% so there have been many mutations taking place over the time these two species split off from a common ancestor about 500,000 years ago. One major difference between humans and Neandertals is that Neandertals did not have a symbolic culture (paintings, engravings, sculptings) in their artifacts. Many anthropologists have surmised they lacked the capacity for a spoken language. There is a gene known as FOXP2 which is essential for human vocalization and mutations in that gene lead to mute or inarticulate speaking. The Neandertal DNA does have FOXP2 but it differs in two of its nucleotides and may have been mute.

Pääbo has synthesized the gene and put the human FOXP2 gene into mice. It changes their activities (more cautious movements), increases cell number in the corpus striatum, leads to more synaptic unions, and diminishes dopamine in the brains of the mice. As Pääbo looks for uniquely human genes he hopes to test these in mice to see how they affect mouse physiology or behavior. He believes this approach over the coming years will teach us how humans differ from other primates as well as from our nearest extinct ancestor, the Neandertals.

Stephen Pinker who also spoke at this symposium suggested that humans might differ from other primates by possessing a “cognitive niche” which allows them to use cause and effect reasoning. This process allows the permutation of several words and ideas into immense combinations and gives humans an edge when facing novel situations. For the rest of the animal kingdom there is a much slower response (often natural selection leading to the loss of many and the survival of a few). If Pinker is correct and this is why humans are so much smarter than other animals, the genes associated with cause-effect reasoning will be among the most likely candidates that define our uniqueness. Language is beneficial to our species because it is given at little cost. As Pinker described it “when you give someone a fish you have surrendered something you had, but when you tell someone how to fish, you do not lose a fish and you do not lose the idea of how to fish.” I would add, you might even get some fish in return out of gratitude.

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RICHARD LEAKY AND THE INSTITUTE FOR HUMAN EVOLUTION


Richard Leaky is an autodidact and high school dropout who is one of the world’s leading anthropologists. He is also a Visiting Professor at Stony Brook University and has been here these past seven years thanks to the efforts of President Kenny and Dean Lawrence Martin, a fellow anthropologist. Leaky was raised in Kenya and learned early from his father how to survive in the bush. He chose to drop out of school and set his own course in human paleontology, sometimes working with his father and sometimes on his own. He is one of the most renowned citizens of Kenya and established a national museum in Mombassa.

Leaky’s vision, when he joined the SBU faculty, was establishing an international center for the study of human origins. He raised several million dollars for this project so that graduate students and postdoctoral students (especially from Africa) could participate in field trips, and in the careful analysis of specimens. He also used the Institute for an annual meeting to bring anthropologists studying human origins from around the world to the Stony Brook campus. A unique feature of this conference is that after the public presentation of their papers, the 100 or so scholars get together for four days on the Stony Brook campus and discuss their work informally and “open old sores and generate new ideas.”

I enjoyed talking with Professor Leaky. He lost his legs in an airplane accident and manages to get around with his artificial ones. He considers himself a Kenyan and spends part of his time at Stony Brook, part in Kenya, and part traveling around the world. As he gets older, travel becomes more difficult but he keeps up his optimism and uses the enthusiasm of his gaining new knowledge as a way to keep going. He is planning a web site (very likely with National Geographic) for human origins that will enable millions of people around the world to see the specimens, follow the analysis, enjoy the debates among anthropologists, and find pleasure in reconstructing their ancestry over the past several millions of years since human-like form and behavior began to emerge. He also hopes his fellow anthropologists will play a leading role in countering the “disrespect for science” shown by those who would offer bad science, dilute the findings of evolution, or pretend to scientific knowledge with a hidden religious agenda substituting supernatural interpretations for scientific ones.

Leaky said this is one of the most exciting times to be an anthropologist. The work on finding new fossil humans and their ancestors is increasing around the world. He cited the findings in Indonesia of the small Homo erectus-like specimens called H. floresiensis. He also found the confirmation of fossil sequences and age through DNA analysis (especially comparative genomics) exhilarating. He felt the United States had more resources and opportunities to learn than any country on earth and he hopes his institute will help foster a greater interest among the public in our ancient ancestry.