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The ancient art of nit-picking

Jessa Netting discovers that nits may have been holing up on human heads for far longer than we thought.
24 July 2000

JESSA NETTING


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Feeling itchy yet? A head louse getting ready to hatch.

No one loves a 'nit-picker', but in times gone by such an obsessive eye for detail was invaluable. That's because 'nits' are the eggs of the human head louse (Pediculus humanus capitatus). The need to pluck them out of the hair of our fellow humans has tapered off recently, but lice have been with us for several thousand years. Now an archaeological find in South America pushes the association back even further in time.

Lice turn up in archaeological sites from Iceland to Israel. Egyptian mummies have been found preserved in their eternal rest along with the lice that shared their lives. More recent Peruvian mummies also boast healthy crops of these 'ectoparasites'.

The latest find, a louse egg cemented to a human hair from a site in northeastern Brazil, beats all of these. Radiocarbon dating of the hair and associated artifacts places them at around 10,000 years old.

Based on this dating, the egg is the oldest yet found and the first evidence of lice east of the Andes, Karl Reinhard of the University of Nebraska-Lincoln and his colleagues report in Parasitology Today1. This earliest example of a louse-human association in the New World, they say, may provide "new insight into the co-evolutionary history of humans and parasites."

The date of the find suggests that lice hitched a ride to the New World on the heads of its very first colonists, adapting to the changing conditions and perhaps evolving into new strains as people dispersed.

According to Reinhard, this contradicts a long-held belief that the first inhabitants of the Americas were pathogen and parasite free. "The lack of parasites is part of a broader perception that there was very little disease in the New World," he says. Reinhard specializes in 'archaeoparasitology' -- the convergence of archaeology and parasitology.

Michael Kliks, a University of Hawaii entomologist who also studies ancient parasite-human associations in the Americas, is cautious about the significance of the find, feeling that previous claims from the same team have been too far-reaching.

Nonetheless, this latest bit of archaeoparasitology could have wider implications. The louse that now inhabits modern New World Monkeys may have evolved from the one crawling through the hair of our ancestors, Reinhard's group suggests, through early contact between monkeys and humans. Learning about how this parasite may have switched hosts could help us understand how other disease-carrying parasites, and the pathogens they transmit, moved the other way: from animals to humans.

References

  1. Araujo, A. Ferreira, L. F., Guidon, Maues da Serra Freire, N., Reinhard, K. J. & Dittmar, K. Ten thousand years of head lice infection. Parasitology Today 16, 269 (2000).
  2. Kenward, H. Pubic lice (Pthirus pubis L.) were present in Roman and Medieval Britain. Antiquity 73, 911 - 915 (1999).

Nature News Service / Macmillan Magazines Ltd 2003

 

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