Human DNA discovered in ancient mummies”lice glue’ revealed South American heritage

31st December, 2021.      //   General Interest  // 

mummy

A recent study has discovered that human genetic material retrieved from the “cement” used by head lice to bind their eggs to hairs thousands of years ago can offer crucial information about ancient people and their travel patterns. Researchers from the University of Reading in the United Kingdom were the first to retrieve human DNA from this cement-like substance on hairs collected from mummified remains dating back 1,500 to 2,000 years.

Female lice make this cement as they attach eggs — known as nits — to the hair, and some skin cells from the scalp become enclosed in the glue-like substance in the process, according to the researchers. “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 the sticky substance produced by headlice on our hair can preserve our genetic information,” Alejandra Perotti of the University of Reading, who led the study, said in a statement.

“Lice biology, in addition to genetics, can reveal important insights about how people lived and died thousands of years ago,” said Dr. Perotti, an Associate Professor of Invertebrate Biology. Researchers extracted DNA from nit cement of specimens collected from a number of mummified remains of people who reached the Andes mountains of the San Juan province in central west Argentina between 1,500 and 2,000 years ago, according to a new study published in the journal Molecular Biology and Evolution on Tuesday.

Scientists also looked at ancient nits on human hair used in textiles from Chile, as well as nits on a shrunken head from the Amazonian Ecuadorian Jivaroan people. Using the new method, researchers could find a genetic link between three of the mummies and humans in Amazonia 2,000 years ago, showing for the first time that the original population of the San Juan province migrated from the land and rainforests of the Amazon in the north of the continent.

“The genetic affinities deciphered from genome-wide analyses of this DNA inform that this population migrated from north-west Amazonia to the Andes of central-west Argentina,” the researchers wrote in the study.

They found that this new technique for recovering ancient human DNA offered better quality genetic material than that extracted through several other methods, offering new clues about pre-Columbian human migration patterns within South America.

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Human hair with a nit attached to it with ‘cement’ (University of Reading)

Until now, archaeologists have extracted ancient DNA preferably from the dense bone from the skull or from inside teeth, as these provide the best quality samples. However, skull and teeth remains are not always available, and it can also be unethical or against cultural beliefs to take samples from indigenous early remains. In several cases, destructive sampling methods also cause severe damage to the specimens that can compromise scientific analysis.

Perotti and his team believe that recovering DNA from the cement delivered by lice could thus be a solution to the problem, especially since nits are commonly found on the hair and clothes of well-preserved and mummified humans.

Researchers say this new method can enable more samples to be studied from human remains in cases where bone and tooth samples are unavailable.

“Headlice have accompanied humans throughout their entire existence, so this new method could open the door to a goldmine of information about our ancestors, while preserving unique specimens,” Dr Perotti said. Some of the nit samples used in the study contained the same concentration of DNA as a tooth, double that of bone remains, and four times that recovered from blood inside far more recent lice specimens, the scientists said.

In the DNA recovered from nit cement in one of the mummies, researchers also found the earliest direct evidence of Merkel cell Polymavirus, which they say on rare occasions could get into the body and cause skin cancer. They believe the new method could reveal clues about the conditions in which a person lived and also provide hints to possible ancient viral diseases.

“The high amount of DNA yield from these nit cements really came as a surprise to us and 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,” the study’s first author Mikkel Winther Pedersen from the University of Copenhagen said in a statement.

“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.” Dr Pedersen added.

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