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March 14, 2007

Hairy Question Untangled By Lice

I cannot say I have ever pondered when we, as former apes, dispensed with the body hair. I guess I assumed it must be at some point after we had either solved the body warmth & protection problems ourselves (through living arrangements or the invention of fashion) thus making body hair obsolete, or if the problems didn't exist because we were living in such a warm habitat that it was a detriment (if so, why didn't other species change at a similar time?). Still, had I decided to ponder this question, it has some interesting problems associated with it. Hair, skin and cloth are not particularly durable or long-lasting materials like fossils. Over time, they deteriorate and our evidentiary support disappears.

Luckily some clever scientists out there came up with a very interesting way of dating when we shed our body hair for good without the need for evidence. They untangled this puzzle by looking not at humans, but at the evolution of another species that was intimately linked with them. You got it, those lovely little lice!

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.

More At: Newsweek: Beyond Stones & Bones

The article above is certainly about more than just this lousy discovery, but I thought that was the most eye-opening. This critical look at inter-species relationships, symbiotic or otherwise, and how scientists are using them to help determine events of evolutionary importance in a species is fascinating. Think of all the stuff living in us, on us, around us. The bacteria alone could answer much, if we can just figure out what questions to ask.

Posted by sorsha at March 14, 2007 11:27 AM