DNA stored in lice glue reveals the secrets of South American mummies | Chemistry

Anyone who has had a hard time picking nits by looking through a magnifying glass knows how female head lice can effectively bond their eggs to human hair. Once these pests have solidified their foothold, they are notorious for being difficult to remove. But even school nurses may be shocked by their true sustainability.Scientists have previously discovered that lice eggs are still stubborn Sticking to ancient hair 10,000 years later..

And now, researchers have found even more remarkable about the use of lice to attach eggs to hair.Invertebrate biologist Alejandr Perotti And her team found that lice cement was excellent at trapping and storing everything it wraps, including high-quality ancient human DNA from lice hosts.Their study was published this week Molecular Biology and Evolution, It was an example of life that imitated art.Played a little like the scene in Jurassic ParkThe dinosaur DNA was sealed in amber after being preserved by mosquitoes that sucked dinosaur blood.

In this case, female lice secreted cement from the glands of the reproductive organs to attach an egg called nito to ancient human hair. Ancient humans later became mummies aged 1,500-2,000 in the Andes, Argentina. In doing so, lice trapped skin cells from the human scalp in cement. Perotti et al. Sequenced the genome from skin cells and discovered that these ancient inhabitants originally came from the rainforests of southern Venezuela and Colombia. In addition, they found that the DNA in the adhesive was kept at the same quality as that normally recovered from teeth, and was superior to other common sources such as the dense pyramidal bone of the skull. Did. This means that in ancient hair, clothing, and other textile examples around the world, lice are ubiquitous, and even if the bodies are gone, valuable DNA that identifies the human host can be produced.

“If you have hair, or if you have clothes, you can find nits on it,” says Perotti of the University of Reading. “By simply examining the DNA trapped in cement, we can study the natural and evolutionary history of thousands of years of hosts and lice.”

Importantly, the methods of Perotti and colleagues allow scientists to study DNA without invasive or destructive techniques such as breaking the skull. This often raises cultural concerns when studying DNA in ancient human bodies.

Team members from five different universities will study South American mummies to learn more about when and how the continent grew. The two lice-bearing lice for this study were buried about 2000 years ago in the high Karingasta cave and rock shelter in the Andes Mountains of today’s San Juan Province in the Midwestern part of Argentina. In this cold, dry area, where even valleys rise to nearly 10,000 feet, mummies were exceptionally preserved along with ectoparasites that share their lives.

Perotti et al. Suspected that DNA might be present in the cement pods used to bond each knit to the mummy’s hair. Using dyes that bind to DNA and special imaging techniques, they revealed that the nuclei of human cells are actually confined and preserved in lice cement. Then a tube was inserted and the DNA was extracted for sampling.

DNA has shown a genetic link between these mummies and individuals who lived in Amazonia 2,000 years ago. Evidence shows that the mountainous Ansirta culture of the region previously came from the rainforest regions of southern Venezuela and Colombia. Such information helps to recreate the prehistoric times of South America. This is especially complicated in Argentina, where many indigenous groups were eradicated, assimilated, or deported centuries ago.

To confirm their findings, the team also analyzed DNA from Nito itself and compared it to other known lice populations. They found that the parasite migration history reflected the migration history of the human host from the Amazon to the Andes.

“All the knits we analyzed gave the same origin,” says Perotti. “It was very interesting. It was completely independent of the host’s DNA and gave us the same evolutionary history.”

The team has also found a source of environmental DNA that is neither human nor lice, as lice cement preserves everything it wraps. Together with various strains, they found the earliest evidence of Merkel cell polymer virus. Discovered in 2008, the virus can cause skin cancer, and researchers now speculate that head lice may play a role in its spread.

The team also looked at knit morphology and attachment to get information about the host’s life. For example, lice lay eggs close to the warmth of the scalp in cold environments, and the location of these knits near the mummy’s scalp exposes them to the extremely low temperatures that ancient humans may have affected their death. Suggested that it was done.

“This work is noteworthy on several levels,” he says. David reid He was a biologist at the Florida Museum of Natural History and was not involved in the study. “First, the author was able to sequence the genome from such a small, seemingly insignificant starting material, and second, these head lice contributed to the understanding of human migration. did.”

Lots of evidence show that our ancestors lived with lice for millions of years.But scientists are only now Dig into the louse genome To clarify how parasites migrated, spread, and evolved with primates and later human hosts around the world.

“Human lice have taught us a lot about our history, from contact with old-fashioned apes to when humans began to wear clothes,” says Reed. “Lice still seem to have more to say about our history.”

Mummies and archaeological surveys confirmed that many ancient groups supported a significant number of populations, both head and garment lice.Scientists Discover a special comb Its prehistoric South Americans were hired to try to get rid of pests. Fortunately for today’s scientists, these efforts have often failed.

Museums and personal collections are full of lice, scattered around hair, textiles and clothing. Many of these archaeological materials are now completely out of context, collected from unknown locations many generations ago, and not linked to any particular location or time. However, Nito, who endures these artifacts even after the human host has fallen into oblivion, is now a newly discovered resource to learn more about their ancient owners.

“The advantage of collecting information from knits is that they have been preserved for thousands of years and adhered to hair and clothing,” says Perotti. “And now we can link them directly to a specific person.”