The complex genetic prehistory of America

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The complex genetic prehistory of America







As part of a large international study, the DNA of a series of famous and controversial ancient remains from North and South America, including an ancient skeleton of 10,600 years of the so-called 'Cave of the Spirit Mummy', has been genetically analyzed. the oldest human mummy found in North America, the remains of Lagoa Santa (Brazil), an Inca mummy and the oldest remains of Chilean Patagonia. In addition, they also studied the second oldest human remains of the Trail Creek Cave in Alaska: a 9,000-year-old baby tooth from a girl.



Previous genomic research suggested that the first American populations separated from their Siberian and East Asian ancestors almost 25,000 years ago, then split into different populations in North and South America about 10,000 years later.



Now, the team of researchers has sequenced the genomes of these 15 ancient Americans - spanning the entire American continent, from Alaska to Patagonia - six of which were more than 10,000 years old. The results show the complex image of the expansion and diversification of the population.



The journal Science has just published the results, which have the participation of Antonio Salas Ellacuriaga, researcher at the Faculty of Medicine of the University of Santiago de Compostela (USC), as well as scientists from Denmark, Canada, England, United States, Brazil, Argentina, Armenia, Chile, Germany or Switzerland.







Skulls and other human remains of Lagoa Santa, Brazil, kept in the Museum of Natural History of Denmark. (Photo: Natural History Museum of Denmark)



Never before had such a result been achieved and never before had such a precise portrait of how the colonization of the American continent took place, the population movements through which the communities of this region of the planet were formed and how the Genome of current populations have been reflected in these early moments of human prehistory in the American continent.



"During the last decade, works of a dozen isolated genomes extracted from archaeological remains were published, each of which allowed" very interesting, but immature "work lines, explains Salas.



The magnitude of the discoveries have a singular scope. "There are so many conclusions that it is difficult to summarize the significance of the findings. It is striking the amount of information that can accommodate a single genome, "says Salas.



The study focuses on the model of expansion of American populations from their earliest beginnings more than 25,000 years ago, since these proto-American populations diverge from their neighbors and ancestors in Siberia and East Asia.



Most of the native-American variability derives from an ancestral group that lived in Alaska and in the Yukon territory, approximately 23,000 years ago.



This population, the scientist clarifies, is divided "into at least two groups: one will give rise to all the Native American populations that we know today and the other remains in the region of Alaska, what we now call ancient Beringians." The latter did not leave descendants and "their existence can only be deduced from the analysis of the genome of archaeological remains".



"Today we know that people inhabited Alaska at least 14,000 years ago," says the scientist, for whom the analyzes allow "to specify the time and place where this population division could have taken place between the ancient Beringians and the ancestors of all Native Americans today, key to the colonization of the entire continent. "



According to the team in charge of the work, "from approximately 17,500 to 14,600 years ago there is a greater division in North America among the people that would give rise to the North Americans and the South Americans."



In addition, the study shows the existence of a "mysterious genetic component of austral-Asian origin, closer to Australian populations, of New Guinea, with an age of at least 10,400 years." On this finding Salas states that "we detected the existence of a phantom DNA that we do not know how it could reach America: it is detected in Brazil, that is, on the east side of the Andes, a location that adds more mystery, although our hypothesis is that comes from the American North side. "



The first entry of proto-Americans occurred by the east of the Beringia and extended to non-glacial areas of North America. This entry of populations through the Beringio bridge has been happening for approximately 25,000 years until approximately 13,000 years ago.



Analyzed genomes suggest the existence of several population subdivisions: in Beringia itself and around Big Bar Lake in the region of British Columbia in Canada. In that period, a representation of this native population is dispersed throughout the rest of the North American continent, "it will be the population that will later give rise to the inhabitants of South America."



The second important period implies the colonization of almost the entire continent to the south, until reaching Patagonia. The data indicate that "this process was very rapid and took place, not gradually, but rather as small steps of colonization".



The work indicates that it would have begun 14,000 years ago and would continue for another eight thousand years. The first settlers of South America "probably took with them an austral-Asian component in their genomes," clarifies the researcher, adding that "we know that this genetic signal is present in Brazil 10,400 years ago," we still have not been able to find one single older genome or more to the north of Laguna Santa with this component ".



On the other hand, from the first colonizations of the south of the continent there were two great routes of emigration, one on each side of the Andes. At the same time, the populations that gave rise to the North Americans and those that gave rise to the native South Americans were also mixed 9,000 years ago in North America.



A third important movement in the continent began in Mesoamerica 8,700 years ago, with movements of populations to the north, in what is known as the Great Basin, located in northwestern North America. On the other hand, a second wave of population expansion towards the south of America begins that will give rise to most of the genetic variability observed today in the south.



Salas believes that we are living "what is probably the most exciting time in genomics. Technological advances are allowing us not to approach and understand complex diseases and their causes in a much more elaborate way, but also to sharpen enormously on issues that have to do with our origins, with what we are and how we have evolved with the passage of weather". (Source: SINC)

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