In a scene from the movie Jurassic Park, the director Steven Spielberg, Billionaire philanthropist John Hammond explains to his team of scientists how his team discovered the fossilized mosquito in amber. This discovery allowed the extraction of DNA from dinosaurs, which have been preserved for over 65 million years.
Of course since this is a science fiction movie. “You can’t really extract DNA preserved in amber,” says Maria Alejandra Perotti, professor of invertebrate biology at the University of Reading. England.
But that does not mean that this technique is not possible. It precisely achieved the bread. Like Hammond, she was able to extract DNA, not from dinosaurs and mosquitoes, but from ancient humans and lice.
Barotti is from Argentina England For nearly 20 years he has been exploring the scientific and historical significance of invertebrates (especially lice) to humans: one of the questions everyone asks: Where did we come from?
But he takes the question further to the regional level: What was the population of South America like?
A team of scientists from the five universities she co-found found that lice became the source of “very good quality” genetic information from the “cement” mummies they use to attach their hair (eggs). The 2,000-year-old was discovered and preserved in San Juan. Argentina, Near the Andes Mountains.
Mummy lice: ‘Cement’ used to attach lice to human hair has become a source of genetic information for 2,000-year-old mummies found in San Juan, Argentina – photo: g1
Unlike modern humans, our ancestors did not have effective methods of removing lice, which can cause real infection on the scalp and clothing.
The female lays eggs that stick to their host with extraordinary efficiency, and in some cases, they have been there for thousands of years.
Lice can be annoying to their former hosts, but for scientists like Perotti, the good news is that they stay that way for a long time.
Knowing that lice could study the evolutionary history of humans, he sought out specimens of human remains containing hair.
Because of its characteristics, Knight will remain intact for thousands of years surrounded by its own “glue”. Human cells can be found within that object.
“Yes, it’s like Jurassic Park,” Perotti told BBC Mundo. “Of course the movie is fictional, but we make analogies because the goal is the same: to classify an object produced by a parasite into a host by a parasite.”
The human DNA found in these samples proved to be of excellent quality, as can be extracted from the petrus bone behind the teeth and ear.
Thanks to this, scientists have discovered additional details such as the ancient population of South America and these mummies, migration routes to the continent, gender and possible causes of death.
“It’s very interesting,” Perotti told BBC Mundo. “The lice always catch my attention because they live so close to the host and act like a mirror. I started using them to explain what happened to the host.”
“Thanks to them, we can read thousands of years of history. They are the mirror of evolutionary history.”
A reflection of ancient humans
There are two subspecies of lice that infect humans Lice: The Body (Of the body) and Pillow (From head).
Thousands of years ago, the Body In addition to the epidermis, it also adapts to live in clothing. Ancient men began to cover themselves with fur and cloth.
This is a demonstration of how the human lice evolved along with its hosts.
Barotti was aware of this relationship and began to study ancient collections in natural history museums to study the history of our ancestors from parasites.
University in Reading Program (England), Oxford University Museum of Natural History (England), Bangalore University (Wales) And San Juan National University (Argentina) In 2016, they hired scientists from the University of Copenhagen (Denmark) To analyze human DNA.
The results were published in the journal Molecular Biology and Evolution.
“I’m been looking for specimens from the original indigenous peoples of South America. I did more research until I had access to collections of human remains containing hair.”
These specimens were taken from preserved mummies Argentina, Excluding other human remains, with different dates, dating back 1,300 to 2,000 years, were discovered in the Calingasta Caves in San Juan Province. For this analysis, the team did not take more than six nits per mummy.
Extracting DNA from these older specimens is not easy and is sometimes considered controversial, especially in well-preserved specimens.
Genetic material is usually extracted from teeth or petrus bone, which indicates their destruction.
The model must meet certain requirements and be in good condition. This is not always possible, and sometimes the material is destroyed or partially damaged.
Through the study of lice, the scientists realized that many inconveniences had been avoided and protected the specimens for further study.
The original idea was to extract human DNA from the same pens that were preserved.
But they were surprised to find that the “rap” that covered the tip was embedded in human DNA, not only because it was “of the highest quality” but also because it was so well preserved by the chemical properties of the glue, explains Michael Winter Pederson. University of Copenhagen ..
“Once the egg gets stuck in the hair, it immediately absorbs the skin cells, probably from the scalp,” he says.
“The interesting thing here is that (the material) is protected from decay. Everything, including me, will decay. Over time, we will disappear. And these models are still here,” he insists.
Migration pathways and diseases
What did the scientists find?
One of the 2,000-year-old mummies belongs to a person from northern Amazonia. They know this because the extracted DNA is matched with other indigenous peoples previously analyzed from the south. Colombia And yes Venezuela.
Others, the most recent (1,300 to 1,500 years old), do not have the same genetic characteristics, so they have different origins: from Patagonia, from the south.
All of this reveals that there was a large expatriate movement in the area thousands of years ago. Those coming from the north may have gone east, and may have been driven by drought-like climate change. “But we do not know how far they have come in the south,” Perotti admits.
These methods were suggested by anthropological studies unrelated to genetics many years ago. But DNA discoveries could provide additional clues as to how humans were distributed across the continent thousands of years ago.
They know this because in an environment with very low temperatures, the nits will be closer to the scalp, where there will be more heat.
Because nit’s glue contains not only human DNA but everything around it, scientists have also discovered non-lice or non-host genetic material. This is the oldest evidence of Merkel’s cell poliovirus.
The virus, discovered in the United States in 2008, is suspected to cause most of the cases of Merkel’s cell carcinoma, a rare but invasive form of skin cancer. Experts now suspect that the lice may have something to do with the spread of the virus.
To support the findings, the team also analyzed the DNA of the lice, and what they found was that they had a migration pattern similar to their hosts.
“There is a lot of interest in learning about the history of South America, even from Europe, the United States and Asia,” says Perotti. “South America has received the last anatomical displacement of modern humans. Humans have been studied all over the world, but there are no focused and accurate studies to find out what happened in South America.”
“For me, a Latin American, I’m proud to have done this research,” he concludes.
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