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The remnants of lice infestations found on ancient mummies can unlock the DNA of those that lived thousands of years ago, said research published by Molecular Biology and Evolution on Tuesday.
It's inevitable that many will deal with a case of head lice at some point in their lives—and, apparently, it's an affliction that ancient humans dealt with, too. As the study's author, Alejandra Perotti, noted in 2018, "the reality is that humans have had head lice living on them for thousands of years."
"They were so common in the past that almost every family was in possession of a special comb to remove and keep them under control or in low numbers," she said, adding that these combs were often made of bone, wood or cactus spine.
According to the new study, per Smithsonian Magazine, researchers looked at mummies from Argentina's Andes Mountains dating back 1,500 to 2,000 years. On these bodies' scalps, scientists uncovered "lice cement": a substance secreted by female lice in order to attach nits (eggs) to hair.
As it turns out, this lice glue is remarkable in its ability to preserve the DNA of the hair and skin cells it encases—meaning that researchers were able to access otherwise-unknown information about the mummies.
"If you have hair, or if you have clothing, you can find nits attached," said Perotti, per Smithsonian. "We can study thousands of years of the hosts', and lice's, natural and evolutionary history just by examining the DNA trapped in the cement."
In particular, the research confirmed the migration patterns of these ancient humans, noted the Independent. By sequencing the skin cells' genomes, scientists learned that the South American mummies were part of a population that had migrated from the rainforests of Amazonia to the Andes mountains of present-day Argentina at least 2,000 years ago.
The method of sourcing ancient DNA via lice glue is a huge step, as other methods of accessing this information (via bones or teeth, for example) are often prohibited because they cause damage to the bodies.
According to researchers, the cells preserved in lice cement yielded the same amount of DNA as would be found in a human tooth—and twice as much as the petrous bone of a skull.
"We know quite a lot about Europe and east Asia from ancient genetics, but America still seems to be quite a blank spot," said study author Mikkel Pedersen, reported the Independent. "This is one of the places we really want to try to see if we can get some genetic information about what's going on in the past, who was there, and also filling in that blank spot."
