Hitchhiker's Guide to the New World

Courtesy of CDC

US researchers are looking to otherwise unwanted guests to piece together humans' evolutionary past: lice. They suggest that modern Homo sapiens may have had direct physical contact with Homo erectus in Asia before crossing over to the New World.

Florida Museum of Natural History's David Reed and colleagues present evidence that the New World lineage of head and body lice coevolved with H. erectus, but switched hosts to H. sapiens around 25,000 years ago.¹ The effective isolation of New World human populations until only a few hundred years ago allowed this louse lineage to persist.

"I think that the conclusion that there was contact between remnant Homo erectus populations and modern Homo sapiens is correct, but the exact nature of that contact will be a continuing controversy," says Todd Disotell, of New York University's Department of Anthropology.

Others are less convinced. Mark Stoneking, at...