Head Lice DNA Reveals The First Interaction of Americas And Europeans, Study Says

For scientists interested in how humans originated and spread over the world, the blood-sucking parasite, Pediculus humanus, has a treasure trove of genetic material that, as new research indicated, is shedding light on some of humanity's most pressing problems.

A new study suggested the genetics of head lice can give information on when and where human tribes split and came together in the past.

European And American Lice Related

In a research article published in PLOS ONE, the authors give evidence that European and American lice are genetically related, dating back to European colonization of the Americas.

274 lice were collected from around the world, including a couple from schools in Mexico and Argentina.

The researchers sequenced the insects' DNA and identified microsatellites, which are short, repeated sequences.

Lice that share these segments inherited them from a common ancestor, providing researchers with a mechanism for classifying the parasites into closely related families.

According to the study's author and molecular biologist in the U.S. Department of Agriculture, Marina Ascunce, one cluster of microsatellites revealed a genetic relationship between lice in Asia and Central America, representing the early movement of people from East Asia into the Americas.

Another cluster of lice linked the Americas and Europe.

The researchers might determine when Indigenous American lice would have mixed with European lice based on how quickly the lice multiply and accumulate the genetic changes that lead to microsatellites.

They discovered that the most plausible response was around 500 years ago, during the time of European colonization.

"I see this as a proof of concept that human lice are good markers for human evolution and migration," Ascunce said. "We can see the louse DNA reflected in our own history."

Understand The Past Through Parasite

It's not the first time academics have used lice genetic variation to better understand the ancient history of the insects' hosts.

According to a report released in 2010, genetic analysis of clothes or body lice, one of three lice that dwell on humans, found that humans likely began wearing some type of clothing at least 83,000 years ago.

David Reed, a coauthor of the current study and a researcher and curator at the Florida Museum of Natural History, discovered 20 years ago that human head lice are made up of two ancient lineages that predate Homo sapiens.

A 2004 study revealed that our species had had direct contact-at least close enough to rub shoulders with ancient people like Neanderthals.

The groundbreaking hypothesis was later confirmed when the first Neanderthal DNA was sequenced in 2010, indicating that Homo sapiens had previously encountered and had children with Neanderthals.

Ascunce said she anticipated the findings would disclose whether Neanderthal head lice are still present today, but the 15 genetic markers, known as "microsatellites," found in the lice's nuclear DNA did not reveal that information.

"Because very little was known about the louse genome when we started the study, we used markers that have a high mutation rate, so we were not able to answer those questions," she said.