|Image Credit: Gilles San Martin/ Wikimedia Commons
Scientists have recovered human DNA from the ‘cement’ that head lice use to bind their eggs to hairs potentially opening up a new window into the past. In a recently published study, DNA was extracted for the first time from cement on hairs obtained from mummified corpses dating back 1,500-2,000 years. As female lice attach eggs, known as nits, to the hair, skin cells from the scalp also get enclosed in the cement made by female lice, saving them from decay for a considerable period.
The University of Reading led the study, which also included other researchers from Argentina, Wales and Denmark. The findings of the study were published in Molecular Biology and Evolution.
A mummified adult man of the Ansilta culture, from the Andes of San Juan, Argentina, dating back approx 2,000 years. Credit: Universidad Nacional de San Juan
Ancient DNA has been retrieved mostly from thick bone from the skull or from within teeth, as these materials are of the highest quality and last the test of time. However, skull and tooth remains are not always available. Collecting indigenous early remains might be immoral or against cultural values, and such sampling also causes serious damage to the specimens, jeopardising future scientific research. As nits are regularly discovered on the hair and garments of well preserved and mummified humans, recovering DNA from the cement provided by lice is a handy solution that can preserve the integrity of the specimen for much longer.
Associate Professor in Invertebrate Biology at the University of Reading, Dr Alejandra Perotti, who led the research, said: “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 head lice on our hair. In addition to genetics, lice biology can provide valuable clues about how people lived and died thousands of years ago. Demand for DNA samples from ancient human remains has grown in recent years as we seek to understand migration and diversity in ancient human populations. Head Lice 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.”
|A human hair with a nit attached to it with ‘cement’. Credit: University of Reading
The DNA quantity in the samples utilizing nit cement was found to be the same as a tooth, double that of bone remains, and four times that of blood retrieved from considerably more recent lice specimens. Over the years, there has been a serious hunt for alternate sources of ancient human DNA and this study has shown that nit cement could be one of those promising options. This discovery has allowed scientists to infer information about a person and their living situations based on the position of nits on their hair and the length of cement tubes. The interpretation of the biology of the nits might reveal their health and possibly even their cause of death.
Dr Mikkel Winther Pedersen from the GLOBE Institute at the University of Copenhagen, and first author of the published paper said: “The high amount of DNA yield from these nit cement 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.”
Hopefully, these new findings will help to shed more light on ancestral heritage and everyone can look forward to a future where there is a much brighter vision of the past.