When and by what means did humans first arrive in North America ? The answers to these questions are still incomplete but a recent discovery brings new information.
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The arrival of Man in America constitutes the last phase of the “exit Africa ”of modern humans, during the late Pleistocene . The date of this arrival is however controversial and estimates range between -20,000 and -13,000 years. These uncertainties are mainly due to the fact that cultural objects or fossils have an uncertain provenance.
A study published in the Science journal allows on the other hand to date a human presence in America with certainty because they are footprints fossils which have been analyzed.
Footprints … and the division of labor?
Unlike conventional fossils, fossilized human footprints undoubtedly attest to the human presence in a given place. They make it possible to date this presence when they are discovered in a sedimentary sequence whose chronology is well known.
Human footprints have thus been dated from there to less 23,000 years, that is during the last glacial maximum , at White Sands National Park, New Mexico. Most of the prints are those of children and adolescents, which the authors explain by the division of labor. The activities which required experience were indeed probably carried out by adults while the youngest carried materials or food.
Colonization of America by humans told by bacteria
If modern man came from Africa, how to know, when the fossils are not enough, which are the routes which it took to colonize the emerged lands of the planet?
It is therefore possible to analyze the bacterial strains of human populations to understand what was the journey of our ancestors.
Article from Fiji Berio , published 06/19/21
The bacteria are often perceived negatively by humans, but our survival depends largely on some of them which constitute in particular our intestinal microbiota and can represent up to 2 kg of the total mass of an adult.
The composition of bacterial flora varies from individual to another depending, for example, on the diet, but also on the human population in which it is present.
A team of researchers from the University from Venda, South Africa, led by Professor Yoshan Moodley was interested in the sequences genetic of the bacteria Helicobacter pylori,
because it is present in the stomach of half of the current human population; the objective being to find the origin of the colonization of North America by Man. The authors of the study published in PNAS
on June 14 revealed a new subpopulation of this bacterium in Siberia . They relied on a existing database containing the genetic sequences of H.
and on a comparative statistical method to solve the riddle of the first arrival of modern humans in the Americas.
Researchers now show that one of the populations of bacteria present in a people native in America was common on a large scale among the humans of Siberia.
This discovery therefore suggests that the American population in question has a Siberian origin. Genetic models also provide a colonization scenario which would probably have consisted of a single migratory event 12,000 years ago.
Ice Age conducive to human migration
The authors recall that modern man appeared in Africa and that a small group left this continent about 60,000 years ago to settle in Eurasia. Almost 50,000 years later, at the end of the Ice Age , modern man had already reached the American continent and traveled the longest possible route, if it was done on foot, from Africa. It is today, impossible to make this trip by walking, but 12,000 years ago the Earth entered a period of glaciation , which implies that the quantity of water frozen at the poles was much greater than what we observe today and that the sea level was at least 100 meters lower than we know today.
The inconspicuous and small Siberian population that the authors identified thanks to H. pylori
was therefore able to take a passage formed by emerged lands between Eurasia and North America. This road now disappeared allowed them to reach a territory virgin of any human occupation and to gradually colonize it, thus giving birth to the Native Americans which inhabit it nowadays.
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