stones and bones

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Sponsored By NEWSWEEK's Sharon Begley, on why the story of our origins isn't as clear-cut as we had thought. By Sharon Begley NEWSWEEK Updated: 5:58 PM ET Aug 21, 2007 Unlike teeth and skulls and other bones, hair is no match for the pitiless ravages of weather, geologic upheaval and time. So although skulls from millions of years ago testify to the increase in brain size as one species of human ancestor evolved into the next, and although the architecture of spine and hips shows when our ancestors first stood erect, the fossil record is silent on when they fully lost their body hair and replaced it with clothing. Which makes it fortunate that Mark Stoneking thought of lice. Head lice live in the hair on the head. But body lice, a larger variety, are misnamed: they live in clothing. Head lice, as a species, go back millions of years, while body lice are a more recent arrival. Stoneking, an evolutionary anthropologist, had a hunch that he could calculate when body lice evolved from head lice by comparing the two varieties' DNA, which accumulates changes at a regular rate. (It's like calculating how long it took a typist to produce a document if you know he makes six typos per minute.) That fork in the louse's family tree, he and colleagues at Germany's Max Planck Institute for Evolutionary Anthropology concluded, occurred no more than 114,000 years ago. Since new kinds of creatures tend to appear when a new habitat does, that's when human ancestors must have lost their body hair for good—and made up for it with clothing that, besides keeping them warm, provided a home for the newly evolved louse. If you had asked paleoanthropologists a generation ago what lice DNA might reveal about how we became human, they would have laughed you out of the room. But research into our origins and evolution has come a long way. Starting with the first discovery of a fossil suggesting that a different sort of human once lived on this planet—it was a Neanderthal skull, unearthed in a mine in Germany's Neander Valley in 1856—our species' genealogy was inferred from stones and bones. Fossils and tools testified to our ancestors' origins in Africa, the emergence of their ability to walk upright, the development of toolmaking and more. But now two new storytellers have begun speaking: DNA and brains. The science of human evolution is undergoing its own revolution. Although we tend to see the march of species down through time as a single-file parade, with descendant succeeding ancestor in a neat line, the emerging science shows that the story of our species is far more complicated than Biblical literalists would have it—but also more complex than secular science suspected. By analyzing the DNA of today's humans as well as chimps and other species (even lice), scientists
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are zeroing in on turning points in evolution, such as when and how language and speech developed, and when our ancestors left Africa. DNA can even reveal how many pilgrims made
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This note was uploaded on 05/31/2009 for the course CHEM 21L taught by Professor Roy during the Fall '08 term at Duke.

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stones and bones - Sponsored By Beyond Stones & Bones...

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