How nit glue could help answer headscratchers about our ancestors
An unusual source of ancient human DNA could help scientists unpick details of our ancestors’ lives and answer longstanding questions. The source? Nit glue.
Scientists studying mummified remains from South America that date back 1,500-2,000 years say they have recovered ancient human DNA from the sticky cement produced by head lice to anchor their eggs to hair.
While a number of groups have looked at the potential of parasites to help explore our past, the researchers say the new discovery is the first time nit glue has been found to be a source of ancient human DNA. The revelation is a boon given the difficulties typically involved in extracting DNA, and the damaged state it is often found in.
“By genetically characterising a human host using just a handful of nits, we prevent the destructive sampling of bones and teeth that deteriorate or destroy unique ancient specimens. This also prevents conflicts with indigenous related people as the mummies or skeleton are left intact, only a few hairs containing nits are sufficient,” said Dr Alejandra Perotti of the University of Reading, who led the research.
What is more, the team found the nit glue yielded the same proportion of human DNA as found in a tooth, and twice that found in the petrous bone of the skull.
“The other thing that we also find is that within the cements, within that glue of the nits, DNA seems to be preserved or protected better from chemical damages, [compared to DNA found in the tooth or bone],” said Dr Mikkel Pedersen, of the University of Copenhagen, another author of the research.
The study, published in the journal Molecular Biology and Evolution, reveals how a team of researchers from the UK, Denmark and Argentina analysed the remains of eight South American mummies as a proof of concept for the approach.
The team were able to extract not only ancient human nuclear DNA but also mitochondrial DNA of the lice themselves from the nit cement of two of the mummies, with analysis of both revealing the same story: the mummified individuals were part of a population that migrated from north-west Amazonia to the Andes of central-west Argentina 2,000 years ago or earlier. This confirmed previous theories based on evidence from archeological sites.
“Here we have the direct evidence right from the humans themselves. So that’s the last nail in the coffin,” said Pedersen. The genetic analysis also shed light on the sex of the mummified individuals, while the position of the nits on the hair revealed that at least some of them experienced very low temperatures at the time that they died.
While the approach has limitations – the parasites are unlikely to be found in skeletal remains, for example – the authors said museum collections around the world held rich historical archives of parasites.
Pedersen said the work could help shed light on longstanding mysteries. “We know quite a lot about Europe and east Asia currently from ancient genetics, but America still seems to be quite a blank spot on the genomic landscape,” he said. “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.”