![]() ![]() ![]() “I think many people might be aware of a co-evolutionary relationship between us and the microbiome we carry,” she says. Department of Agriculture and a co-author of the new study, is interested in tracking the relationship of the infamous parasite and its human hosts to learn much about both. Marina Ascunce, an evolutionary geneticist with the U.S. Studies show that human and chimpanzee lice diverged sometime around 5.5 million years ago, roughly the same era as the lineages of their hosts. Lice and their predecessors have been intimately living with primates and co-evolving together for at least 25 million years. Some nits are attached with cement so strong they have been found still stuck to ancient hair after 10,000 years. Their eggs, or nits, won’t hatch unless they stay in a special “Goldilocks zone” near the human scalp. The parasites can’t live more than a day or two away from their human host. Lice are an itchy annoyance, and we are stuck with them. It reminds us that even the less-than-charismatic creatures can be very important to our understanding of the world around us.” “Written in their DNA is a script of our story. “It is amazing to think that the lowly louse can shed a bit of light on our human journey around the world,” says David Reed, a biologist at the Florida Museum of Natural History and a co-author of the study. That revelation shows the insects’ migration patterns mirror the New World mixing of their human hosts from East Asia and Europe. ![]() The only place that the authors of the new research, published Wednesday in PLOS One, found the two lice clades commonly hybridize is in the Americas. While the former louse cluster has populated much of the world, the latter is concentrated in Europe and the New World. Then, thousands of years later, a second louse lineage came over nestled on the heads of European colonists. One group arrived tucked into the hair of the East Asians who first populated the Americas. Now, a study of louse genetics suggests that two distinct clusters of the pests migrated to the Americas with different human hosts. And since lice have their own distinct genetic lineages, evolved while living on humans, we can study them to yield clues about the history of our species. The descendants of those critters cling to us today. The blood-sucking parasites persistently bedded down in human hair and moved with hunter-gatherers from Asia into and throughout the Americas. But another clue to when the first humans arrived in the Americas lives on our bodies-lice. And among descendants on either side of the Bering Strait, genetic studies have helped to map out the whens and wheres of these migrations. The first humans to arrive in America left scattered evidence behind, from ancient stone tools to fossilized footprints. ![]()
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