Thursday, March 15, 2007
Newsweek cover story: Human Evolution
The role of genetics in understanding our human past continues to
increase. Scientists now have a theory as to when humans began
wearing clothes, thanks to genetics and lice.
The New Science of Human Evolution
By Sharon Begley
March 19, 2007 issue - 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 article continues at :
"If we have the truth, it cannot be harmed by investigation." -J. Reuben Clark, D.