What Head Lice Can Tell Us About Human Migration

upstart writes:

'Lice are like living fossils we carry around on our own heads':

Reviled the world over for making our scalps itch and rapidly spreading in schools, lice have hitched their destiny to our hair follicles. They are the oldest known parasites that feed on the blood of humans, so learning more about lice can tell us quite a bit about our own species and migratory patterns.

A study published November 8 in the open-access journal PLOS ONE found that lice likely came into North America in two waves of migration. First when some humans potentially crossed a land bridge that connected Asia with present day Alaska roughly 16,000 years ago during the end of the last ice age and then again during European colonization.

[...] Lice are wingless parasites that live their entire lives on their host and there are three known species that infest humans. Humans and lice have coevolved for thousands of years. The oldest louse specimen known to scientists is 10,000 years old and was found in Brazil in 2000. Since lice and humans have a very intertwined relationship, studying lice can offer clues into human migratory patterns.

[...] Researchers found genetic evidence that head lice mirrored both the movement of people into the Americas from Asia and European colonization after Christopher Columbus's arrival in the late 1400's.

"Central American head lice harbored the Asian background associated with the foundation of the Americas, while South American lice had marks of the European arrival," Ariel Toloza, a study co-author and insect toxicologist at Consejo Nacional de Investigaciones Cientificas y Tecnica (CONICET) in Argentina, tells PopSci. "We also detected a recent human migration from Europe to the Americas after WWII."

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