The delicate distinction of Neanderthal hybrids – Sciences et Avenir

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Humaine Homo sapiens et Humain néandertalien

It was the sequencing of the Neanderthal man’s genome, in the 2000s, that made it possible to confirm that his species had indeed hybridized with ours, Homo sapiens, revealing a complex history of interbreeding between the two human lineages over the last hundred thousand. years. The width of the orbits is among the traits hybridized between Neanderthals and Sapiens Previously, skeletons from Romania and Portugal (see map below) suggested admixture, but they were not unanimous: criticism focused on characters that would have been too uncertain or that they were young adults still growing. It even took until 2015 for the first Neanderthal hybrid fossil to be officially recognized! Today, an American and South African team believe they are able to confidently identify the faces of mestizos after comparing a small number of skulls and developing benchmarks and measurements to characterize hybrid traits, such as the orbits of width Steven E. Churchill, Department of Evolutionary Anthropology, Duke University, Duham (USA) and Clés de Kamryn, Center for Exploring the Human Journey, University of the Witwatersrand, Johannesburg, South Africa) were interested in “Neanderthal midfacial morphology -modern human interbreeding,” an article published in the journal MDPI Biology. “The nature of demographic interactions between Ice Age Neanderthals in Europe and western Asia and the modern humans who eventually replaced them is of particular interest,” the authors explain. It was the sequencing of the Neanderthal man’s genome, in the 2000s, that made it possible to confirm that his species had indeed hybridized with ours, Homo sapiens, revealing a complex history of interbreeding between the two human lineages over the last hundred thousand. years. The width of the orbits is among the traits hybridized between Neanderthals and Sapiens Previously, skeletons from Romania and Portugal (see map below) suggested admixture, but they were not unanimous: criticism focused on characters that would have been too uncertain or that they were young adults still growing. It even took until 2015 for the first Neanderthal hybrid fossil to be officially recognized! Today, an American and South African team believe they are able to confidently identify the faces of mestizos after comparing a small number of skulls and developing benchmarks and measurements to characterize hybrid traits, such as the orbits of width Steven E. Churchill, Department of Evolutionary Anthropology, Duke University, Duham (USA) and Clés de Kamryn, Center for Exploring the Human Journey, University of the Witwatersrand, Johannesburg, South Africa) were interested in “Neanderthal midfacial morphology -modern human interbreeding,” an article published in the journal MDPI Biology. “The nature of demographic interactions between Ice Age Neanderthals in Europe and western Asia and the modern humans who eventually replaced them is of particular interest,” the authors explain. Credit and future sciences. “We used six measurements of the facial skeleton, for example the width and height of the orbits (see our infographic above, editor’s note) and applied them to samples of Neanderthal and early human fossils modern times, Steven E. Churchill explains to Sciences et Future This exploratory study aims to try to identify geographic regions (from the Near East to Western Europe) where interbreeding could have been widespread enough to have left a signal in the facial morphology of humans early moderns of these regions”. The authors acknowledge, however, that the size of the fossil samples studied was very small. Map of western Eurasia showing areas and estimated dates of possible hybridization between Neanderthal humans and the modern species (in red) based on fossil samples from the sites indicated. Ancient DNA from a Neanderthal fossil from Denisova Cave (black dot) has been interpreted to reflect modern Neanderthal-human mixing in the Near East 100,000 or earlier. Here Ka equals 1000 years. Example: The 36 Ka date for Saint-Césaire is equal to 36,000 years. A stream more than a crossing tree For their part, researchers from the University of Tübingen (Germany) and the University of Cape Town (South Africa) also analyzed how hybridization had affected the skeletons in the review Nature Ecology and Evolution. But their results differ from those of the previous team. “Many people living today have a small component of Neanderthal DNA in their genes, suggesting an important role for admixture with archaic human lineages in the evolution of our species,” says Professor Katerina Harvati of the Senckenberg Center for Human Evolution and the Paleoenvironment of the University. from Tübingen, Germany. Paleogenetic evidence indicates that hybridization with Neanderthals and other ancient groups occurred repeatedly, and the history of our species looked more like a web or a braided stream than a tree.” Obviously, the origin of humanity was more complex than previously thought. Measuring the impact of hybridization using fossil skulls and individual potential hybrids identified in the past (see map above) is essential “because ancient DNA is rarely well preserved in specimens fossils, so scientists must recognize possible hybrids from their skeletons. This is vital to understanding our complex past and what makes us human,” adds Professor Rebecca R. Ackermann of the Institute for Research in Human Evolution at the University of Cape Town, South Africa. evidence from the jaw and cranial vault. of fossil remains of humans from the Upper Paleolithic of Eurasia, dating from about 40,000 to 20,000 years ago. Several of these individuals have produced ancient DNA that shows a small component of Neanderthal ancestry in their genes, reflecting their recent admixture with this group. The bones were compared to (unmixed) samples from Neanderthals and ancient and modern humans from Africa. The researchers examined three regions of the skull: the jaw, the cranial vault, and the face, looking for telltale signs of hybridization.” for example, an intermediate morphology compared to Neanderthals or to modern humans, dental abnormalities or unusual sizes. These are features that we see in hybrids of various mammals, including primates,” Harvati and Ackermann explain. Their study showed that signs of hybridization were evident in the cranial vault and jaws, but … not in the faces . , unlike their North American and South African counterparts. In individuals with known genetic backgrounds, the researchers also examined whether signs of hybridization in the skeleton matched the percentage of Neanderthal ancestry. The case suggests that “the presence of particular genetic variants is likely to exceed the overall proportion of Neanderthal ancestry,” the researchers. Harvati and Ackermann also identified some of the individuals studied as potential hybrids, including individuals from the Middle East – well known as contact region for groups-, but also beyond, in Western and Eastern Europe. However, “wherever possible, individual hybrid status should be confirmed through nt genetic data and as such we feel that these identification hypotheses should be tested,” says Katherine Harvati. The two teams look forward to fruitful exchanges to better identify evidence of hybridization in the fossil record tomorrow. “This was the first study of its kind,” he says, adding that “we hope it will encourage researchers to look more closely at these fossils and combine multiple lines of evidence to identify hybridization in the record.” Hydration, innovative of evolution? In other organisms, from plants to large mammals, hybridization is known to produce evolutionary innovation or new abilities. “It is estimated that around 10% of animal species produce hybrids, including, for example, bovids, bears, cats and canines,” explains Rebecca Ackermann. Hybrids are also known in primates, our close relatives, such as baboons. “Because hybridization introduces new variations and creates new combinations of variations, it can facilitate particularly rapid evolution, especially in the face of new or changing environmental conditions.” Thus, hybridization may have provided ancient humans with genetic and anatomical features that gave them significant advantages as Africa spread across the globe, giving rise to our physically diverse and evolutionary resilient species, according to the authors hypotheses that remain to be proven.
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