Head lice found on ancient mummies contain more DNA than a tooth, scientists say, who say it could help shed light on ancient people and migration.
A team was able to extract DNA from the “cement” head lice used to stick their eggs to the hair of mummified bodies in South America thousands of years ago.
The DNA extracted from the cement was of higher quality than that recovered by other methods, according to the team led by the University of Reading.
He revealed clues to pre-Columbian human migration patterns across South America, including the fact that the original population of San Juan Province migrated from Amazonian rainforests and lands to the north of the continent.
“There is a search for alternative sources of ancient human DNA and slow cement could be one of those alternatives,” said the study’s first author, Dr Mikkel Winther Pederson, of the University of Copenhagen. in Denmark.
Head lice found on ancient mummies contain more DNA than a tooth, scientists say, who say it could help shed light on ancient people and migration
MAIN FINDINGS FROM THE SLOW CEMENT ANALYSIS
GENETIC LINK: A genetic link between three of the mummies and humans in the Amazon 2,000 years ago.
This shows for the first time that the original population of the province of San Juan migrated from the lands and rainforests of the Amazon to the north of the continent (south of present-day Venezuela and Colombia).
FOUNDING DNA: All the ancient human remains studied belong to the founding mitochondrial lineages of South America.
MERKEL CELLULAR VIRUS: The first direct evidence of the Merkel cell polymavirus was found in DNA trapped in the nit cement of one of the mummies.
The virus, discovered in 2008, is excreted through healthy human skin and can on rare occasions enter the body and cause skin cancer.
The discovery opens the possibility that head lice could spread the virus.
MIGRATION: DNA analysis of nits confirmed the same migration pattern for human lice, from the northern Amazonian plains to west-central Argentina (San Juan Andes)
They recovered DNA from head lice eggs, or nits, found in the hair of mummified bodies dating back 1,500 to 2,000 years, and were found in Argentina.
“This was possible because the skin cells of the scalp got locked in the cement produced by the female lice when they attach their eggs to the hair,” the researchers explained.
The results include clues on the migration of pre-Columbian peoples from South America that were not available by other methods.
They believe this method could make it possible to study more unique samples from human remains – even when no bone or tooth samples are available.
Dr Alejandra Perotti, associate professor of invertebrate biology at the University of Reading, led the research.
He said: “Like the fictional story of mosquitoes locked in amber in the Jurassic Park movie, carrying the DNA of the dinosaur host, we have shown that our genetic information can be preserved by the sticky substance produced by lice. of head.”
“In addition to genetics, the biology of lice can provide valuable clues as to how people lived and died thousands of years ago,” added Dr Perotti.
“The demand for DNA samples from ancient human remains has increased in recent years as we seek to understand the migration and diversity of ancient human populations.
“Lice have been with humans throughout their existence, so this new method could open the door to a wealth of information about our ancestors, while preserving unique specimens.”
Until now, ancient DNA has been extracted from dense bones in the skull or inside the teeth, as these provide the best quality samples.
However, skull and tooth remains are not always available, as it may be unethical or cultural belief to take samples from the earliest native remains.
The severe damage to specimens caused by destructive sampling also makes such extractions taboo and jeopardizes future scientific analyzes.
Recovering the DNA from the cement released by the lice is therefore a solution to the problem, especially since nits are commonly found on the hair and clothing of well-preserved and mummified humans.
DNA taken from the mummies in Argentina has revealed that they reached the Andes mountains of the province of San Juan, in west-central Argentina.
A team was able to extract DNA from “cement” head lice used to glue their eggs to the hair on mummified bodies in South America thousands of years ago.
NITS MORPHOLOGICAL ANALYSIS RESULTS
VERY COLD: The mummies were likely all exposed to extremely cold temperatures when they died, which could have been a factor in their deaths.
This was indicated by the very small space between the nits and the scalp on the hair shaft.
Lice depend on the heat of the host’s head to keep their eggs warm and therefore deposit them closer to the scalp in cold environments.
OLDER AGE: Shorter tubes of cement on the hair correlated with older and / or less preserved specimens, due to the degradation of the cement over time.
The team also studied ancient nits on human hair used in a textile from Chile and nits from a shrunken head from the ancient Jivaroan people of Amazonian Ecuador.
Samples used for DNA studies on nit cement were found to contain the same concentration of DNA as a tooth, twice that of bone remains and four times that recovered from blood inside samples. of much more recent lice.
Dr Winther Pedersen said: “The large amount of DNA produced by these nitro cements really surprised us and it was striking to me that such small amounts can still give us all this information about who these people were and how. lice linked to other species of lice but also giving us clues about possible viral diseases.
“There is a search for alternative sources of ancient human DNA and Slow Cement could be one of those alternatives. I believe that further studies are needed before really discovering this potential.
In addition to DNA analysis, scientists were also able to draw conclusions about a person and the conditions they lived in from the position of the nits on their hair and the length of the cement tubes.
They were able to determine the sex of human hosts, how populations migrated across South America, and evidence of viruses.
DNA extracted from cement was of higher quality than that recovered by other methods, according to team led by University of Reading
The team has revealed a genetic link between three of the mummies and other humans known to live in the Amazon 2,000 years ago.
“This shows for the first time that the original population of the province of San Juan migrated from the lands and rainforests of the Amazon to the north of the continent, to the region south of present-day Venezuela and Colombia,” said noted the authors.
They also found that all of the ancient human remains studied belonged to the founding mitochondrial lineages of South America.
The mummies were likely all exposed to extremely cold temperatures when they died, which could have been a factor in their deaths.
This was indicated by the very small space between the nits and the scalp on the hair shaft. Lice depend on the heat of the host’s head to keep their eggs warm and therefore deposit them closer to the scalp in cold environments.
Shorter tubes of cement on the hair correlated with older and less preserved specimens, due to the degradation of the cement over time.
In addition to the University of Reading, researchers from the National University of San Juan, Argentina; Bangor University, Wales; the Oxford University Museum of Natural History; and the University of Copenhagen, Denmark were involved.
The results were published in the journal Molecular biology and evolution.
DNA: A COMPLEX CHEMICAL THAT CARRIES GENETIC INFORMATION IN ALMOST ALL ORGANISMS
DNA, or deoxyribonucleic acid, is a complex chemical in almost all organisms that carries genetic information.
It is located in the chromosomes of the cell nucleus and almost all cells in a person’s body have the same DNA.
It is made up of four chemical bases: adenine (A), guanine (G), cytosine (C) and thymine (T).
The double helix structure of DNA arises from the binding of adenine with thymine and the binding of cytosine with guanine.
Human DNA is made up of three billion bases and over 99% of these are the same in all human beings.
The order of the bases determines what information is available to maintain an organism (similar to how letters of the alphabet form sentences).
The bases of DNA pair up with and attach to a sugar molecule and a phosphate molecule as well, combining to form a nucleotide.
These nucleotides are arranged in two long strands that form a spiral called a double helix.
The double helix looks like a ladder with the base pairs forming the rungs and the sugar and phosphate molecules forming vertical side pieces.
A new form of DNA was recently discovered inside living human cells for the first time.
Named i-motif, the shape resembles a twisted “knot” of DNA rather than the famous double helix.
The function of the i-motif is unclear, but experts believe it could be used to “read” DNA sequences and convert them into useful substances.