Human DNA from 2000-year-old headlice opens a new window into the past

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An international team of researchers has successfully extracted human DNA from the ‘cement’ that headlice use to stick their eggs to human hairs. The DNA was recovered from mummies from Argentina that date back about 1,500 to 2,000 years.

“Headlice have accompanied humans throughout their entire existence, so this new method could open the door to a goldmine of information about our ancestors,” Dr Alejandra Perotti, one of the authors of the study said in a press statement Perotti is affiliated with the Ecology and Evolutionary Biology Section at the School of Biological Sciences, University of Reading, UK.

“Like the fictional story of mosquitos encased in amber in the film Jurassic Park, carrying the DNA of the dinosaur host, we have shown that our genetic information can be preserved by the sticky substance produced by headlice on our hair. In addition to genetics, lice biology can provide valuable clues about how people lived and died thousands of years ago,” she explained.

The paper published last week in Molecular Biology and Evolution notes that such lice sheaths can be a new source of high-quality ancient DNA not just from humans but also from a variety of other animals where bones and teeth are not available. The team writes that DNA extracted from nit cement contained the same concentration of DNA as from a tooth and double that from bone remains.

Dr Mikkel Winther Pedersen from the GLOBE institute at the University of Copenhagen, and first author, said: “…it was striking to me that such small amounts could still give us all this information about who these people were, and how the lice related to other lice species but also giving us hints to possible viral diseases. There is a hunt out for alternative sources of ancient human DNA and nit cement might be one of those alternatives. I believe that future studies are needed before we really unravel this potential.”

The analysis of the DNA from nit-cement helped confirm the sex of the human hosts and the genetic link between the mummies and humans in Amazonia. The study also found the earliest direct evidence of Merkel cell Polyomavirus.

The team notes that the cause of death was extreme cold temperatures as there was a very small gap between the nits and the mummy’s scalp. Lice generally rely on the host body heat to keep the eggs warm and lay them close to the scalp in very cold environments.

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