October 22, 2020

Mummies tell the story of the first Americans | Science

Mummies tell the story of the first Americans | Science

After 20 years of legal battle, the Shoshone and Paiutes Indians were able to honor and dismiss the mummy from the cave of the Spirit. Located in 1940 in the Indian reservation of Fallon (Nevada, USA), had been exposed in the state museum until, in the nineties, the dating of their hair showed that it was 10,600 years, making it the oldest natural mummy. The Indians claimed it as their ancestor, but the federal authorities, urged by some scientists, did not give it to them. Such ancient remains could shed a lot of light on the first Americans. The case was in court until a Danish geneticist found a solution: to sequence his genome. The DNA confirmed that the mummy was an ancestor of the current Native Americans, who could fire her in peace.

Now, that Danish researcher, Eske Willeslev, and 50 other scientists present the analysis of the genome of a fortnight of mummies and other remains of ancient Americans, several of them with an age of 10 millennia. His work, published in Science, has allowed us to draw how was the expansion of those first Americans who They crossed the Bering Strait maybe 20,000 years ago.

The map includes from the teeth of a child who lived in what is now Alaska 9,000 years ago to an adult dating back some 6,500 years recovered at the other end of the continent, in the Strait of Magellan. In between, they have also analyzed the DNA of samples throughout the Americas, such as the mummy of Aconcagua, a small sacrifice by the Incas barely 500 years ago, or the thirty humans found in the cave of Sumidouro, in Lagoa Santa (Brazil). The analysis of the latter has been key. Found almost 200 years ago by another Danish, the naturalist Peter Lund, they waited in the cabinets of the Museum of Copenhagen (Denmark) for someone to extract all the information. After a complex process, Willeslev's team was able to extract their DNA and determine that they had 10,400 years, 200 less than the mummy of the Spirit's cave.

Among the sequenced genomes is that of the oldest natural mummy

"Two divergence events [de un ancestro común] almost simultaneously it is extraordinary, the divergence usually needs thousands of years ", says in a telephone conversation the main author of the study, the researcher of Center of Geogenetics of the University of Copenhagen, Víctor Moreno Mayar, despite being separated by 10,000 kilometers from distance, there is hardly any genetic separation between the mummy of the north and the rest of the south. "There was a migration from the north to the south and everything suggests that the expansion was very wide and fast", continues the Mexican scientist. not even in a single moment.

About 8,000 years ago, some of those Native Americans moved again, but this time they left Central America and moved both north and south. Researchers have found the trace of this movement in the genome of all current indigenous populations for which there is genetic data.

However, another study published at the same time that this Science (The two groups of scientists agreed this way), complicates the story. With the genome of 50 individuals from diverse American populations, some with 11,000 years old, this research, published in Cell, argues that there was not a single great migration from north to south. In addition to the one that took humans to Patagonia, there were two others in the following millennia and two from north to south.

"A key finding has been that individuals related to the Clovis culture dated about 12,800 years ago they share a distinctive ancestry with the oldest in Chile, Brazil or Belize, "says co-author of this study and researcher at the Max Planck Institute of Human History Sciences, Cosimo Posth, in a note." This supports the hypothesis that the expansion of the people who spread the Clovis culture across North America also reached Central and South America, "he adds.

The mystery that neither of the two investigations manages to reveal is how, among Native Americans like those of Lagoa Santa, there is a weak but significant sign of the genome of australasian peoples and the south of the Indian Ocean, far removed geographically and genetically from the Amazonian inhabitants. . It does not seem logical that this signal already came with the first ones that crossed the Strait of Bering and, nevertheless, it is not detected neither in the mummy of the Aconcagua, nor in the one of the cave of the Spirit nor in the tooth of the boy of Alaska. Nor could it come in a later wave, since the remains of the Sumidouro cave are 10,400 years ago. Did they arrive by the sea, by the Pacific, as some have maintained?

"It had to be before 10,000 years ago [la datación de Lagoa Santa]. But the technology to navigate the Pacific developed by the Polynesians does not appear until 3,000 years ago, "recalls the Mexican Moreno Mayar, nor does it seem credible that a small population reached the American coasts, crossed the Andes, penetrated into the Amazon rainforest and It will leave its mark.


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