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Prehistory and the DNA of Lice

January 29, 2013

Anthropologists think they know when humans started wearing clothes. How could they possibly know that, you might ask, when clothes don’t fossilize? After all, we’re talking about a period before written records or even cave paintings. The answer comes from the genes of lice.

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The body louse, Pediculus humanus corporis

Body lice belong to the same species as head lice, but they have their own subspecies. They’re Pediculus humanus corporis, while head lice are Pediculus humanus capitis. Body lice have claws adapted to grasping fabric and other materials, rather than hair, and they secure their eggs to clothing. So they need clothes and can’t have evolved from head lice until our ancestors got dressed. Scientists think the bloodsuckers would’ve exploited the new environment pretty quickly after it appeared, so body lice must have split off from head lice around the time clothes came along. Genetic analysis can tell us when two species diverged: when their last common ancestor lived. The answer from studies of Pediculus humanus DNA? Lice split into two subspecies—and people started wearing cloths—sometime between 80,000 and 170,000 years ago.

Interestingly, the Homo sapiens who lived eighty-plus thousand years ago weren’t quite … us. They’re called “anatomically modern humans” because their bodies matched ours (roughly), but their brains apparently didn’t. Anthropologists think they lacked real language. In other words, our ancestors started getting dressed before they could talk.

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© 2013 by David Carthage.

2 Comments leave one →
  1. Neanderthal man with plenty of body hair permalink
    January 30, 2013 8:58 am

    I would have guessed that ancient humans had lots of body hair so that lice didn’t really gain an advantage by grabbing clothing because I’m assuming that lice need to contact human skin.

  2. January 30, 2013 12:35 pm

    Thanks, Neanderthal man! A hair habitat for lice would require thick hair, like the type we’ve got on our heads (most of us). Genetic research on skin color suggests our ancestors lost that kind of thick body covering about a million years ago–before the evolution of Homo sapiens. So even if early humans had a bit more hair than we do, they wouldn’t have offered a home for lice anywhere but on their heads (and their pubic regions, actually, where a completely different louse species lives–crabs!).

    BTW, I’ve never read whether prehistoric people had more hair than we do, or less. But I wouldn’t assume it’s more just because they’re closer in time to ape ancestors. The operative question is “What selective pressures favored more or less body hair?”–rather than “How close is this or that group to apes?”

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