In a creative use of insect genetics to solve an enduring mystery of human evolution, scientists studying the DNA of lice have concluded that early humans may have started wearing clothes just a few tens of thousands of years ago, more recently than many had presumed.
The new work -- based on subtle genetic differences between human body lice, which depend on clothing for their survival, and human head lice, which do not -- suggests early humans may have lived in Europe for tens of thousands of years after leaving Africa before availing themselves of clothes.
Among the work's controversial implications: Early humans such as Neanderthals -- which lived from about 150,000 years ago until 30,000 years ago and which are typically depicted as hairless and clad in furs -- may in fact have been quite furry until surprisingly late in their evolution.
"If you look at how Neanderthals are routinely depicted in books and museums, people have just thought they must have had clothing to protect against cold weather," said study leader Mark Stoneking of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "But if you ask, 'What's the evidence?' it's just not compelling that they had clothes."
The transition from hairy to hairless, and the related advance from naked to clothed, were seminal events in human biological and cultural evolution. But scientists know little about the timing of either.
Fur and fabrics typically rot before they fossilize, so there are no lasting remnants of these coverings more than a few thousand years old. Ancient needles and other artifacts indicate people were weaving and sewing at least 25,000 years ago -- and perhaps as much as 15,000 years before that. But some researchers believe the human trek from naked wilderness to the runways of Paris and Milan began well more than 100,000 years ago.
Anthropologists are especially interested in knowing when people graduated from crude, animal-skin togas to sewn, tailored and decorated clothing -- a major cultural advance that offered new ways to broadcast information.
While several scientists agreed that the new louse study was clever -- calling it "neat," "wonderful," and in the words of one prominent geneticist "way cool" -- all cautioned against reading too much into the findings.
The new work, published in today's issue of the journal Current Biology, focused on parasitic lice.
Individual species of lice are intensely specialized, largely to avoid grooming and preening behaviors by creatures trying to get rid of them. Stoneking took advantage of a specialization that separates head lice and body lice.
By figuring out when body lice first appeared, the team reckoned, they'd get a good idea of when clothing arose.
The researchers first compared the genetic codes of human and chimpanzee lice, to get a measure of how rapidly louse genes mutate.
Then they compared the DNA from 40 different human head and body lice that scientists had mailed them from around the world. Using the molecular metronome of one mutation every 30,000 years, they determined that human body lice branched off from a line of head lice about 72,000 years ago -- suggesting an origin of clothes around that time.