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Teeth analysis suggests that Neanderthals and modern humans are shared even earlier than we thought

A sample of some hominine teeth is analyzed in the new study.
Picture: Aida Gomez-Robles

Evidence from dentists suggests that Neanderthals and modern humans were separated from a common ancestor 800,000 years ago – hundreds of thousands of years earlier than standard estimates. The discovery can finally reveal the origin of our common origin, but some experts say the new evidence is inconclusive.

Archaeological and genetic evidence suggests that Neanderthals were moving around Eurasia about 400,000 years ago and that modern humans, Homo sapiens, emerged in Africa about 300,000 years ago. These two groups of hominins – the two types of people – originate from an unknown common ancestor. The time and geographical location of their significant evolutionary part is not known, but research on skulls and DNA suggests that it happened about 500,000 to 600,000 years ago.

A new study, published this week in the science of progress, suggests that the divergence between Neanderthals and modern humans from our last common ancestor (LCA) occurred no earlier than 800,000 years ago. Lonely author of the new study, Anthropologist Aida Gomez-Robles of University College London, came to this conclusion after analyzing Neanderthal teeth of 430,000 years. The experts we talked with, however, say that more evidence is needed to strengthen this claim.

The Neanderthal teeth used in the study were previously found in Sima de los Huos, a Spanish cave that was hominine during the middle Pleistocene. The remains of nearly 30 people have been found in Sima, and they show anatomical features that are very neanderthal in sight. In fact, they are so neanderthal as scientists think these bones and teeth probably come from an early Neanderthal version.

The layer in which the remains were found was previously dated to 430,000 years. That means the Neanderthals, with their special features, must have separated from our LCA long before. Evolution moves very slowly. But, according to the new research, the characteristics seen in the teeth required to appear more than a few hundred thousand years ago.

"The time of divergence between Neanderthals and modern humans younger than 800,000 years would mean an unexpectedly rapid teeth elimination in the early Neanderthals from Sima de Los Hues," Gomez-Robles said in a statement by UCC. "There are various factors that could potentially explain these results, including the strong selection of changing teeth of these hominins or their isolation from other neanderthals found in continental Europe. However, the simplest explanation is that the divergence between Neanderthals and modern humans was older than 800,000 years. This will make the evolutionary rates of early Neanderthals from Sima de los Huos roughly comparable to those found in other species. "

The hominids at the Sima site had very small atriums and molars, which is in accordance with the Neanderthals. These small dental features have probably developed from the larger teeth of the identified LCA. For the study, Gomez-Robles analyzed the teeth of various types of hominine and used the obtained quantitative data to determine the basic rate of teeth evolution in hominins.

"Sima's teeth are very different from those you would expect them to find in their last common ancestors with modern humans, suggesting that they developed separately over a long period of time to develop such big differences," Gomez-Robles said.

Our common LCA with Neanderthals is not yet known, but this finding suggests that mysterious species can not be too younger than 800,000 years. Hominine type Homo heidelbergensis, which lived from about 800,000 to 300,000 years ago, is now a low probability candidate, according to a new study.

Katerina Duka, an archaeologist at the University of Oxford, who is not related to the new study, said the statistical and modeled analyzes carried out in the study were "very interesting," but the conclusions rely on one basic assumption: the absolute date is fixed for individuals the Sima de Los Hues are actually correct.

"However, we know that Sima's age is not resistant to shooting and if the real age is younger, for example, at the age of 250,000 years, the divergence rates calculated in this study would be compatible with the average evolution rates, and not at all controversial, "Douka explained to Gizmodo in an email.

Sharon Browning, a biostatist at the University of Washington, felt that the new paper rely too heavily on extrapolation made from a single data point, which is the observed distance of the teeth. The newspaper, she told Gizmodo in an email, did not consider enough all other data, especially the divergence of DNA.

"The author claims that the uncertainty in the mutation rates, for example, can affect the results of DNA divergence. This is certainly true, to the point," said Browning. "However, even using the lower end of the reliable mutation rates," previous surveys of 2012 "uncovered a period of Neanderthal division of humans from 600,000 years ago," she said.

Also, the DNA data available for Sima's people are not very complete, and even if their DNA can have similarities with Neanderthals, it is possible that this group is hampered by some other unknown hominins, resulting in observed differences in teeth , according to Browning. This "is only one possibility of aligning dental data with fixed ranges for Neanderthal-human split times," she added.

Indeed, while the new study provides intriguing food for thought, it is clear that more evidence will be needed to strengthen the Gomez-Robles conclusion. Until then, the last common ancestor of Neanderthals and modern humans will have to remain a permanent mystery.

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