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
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.
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