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WASHINGTON, Aug. 22 – The remains of a prehistoric primate who lived high in the Andes 20 million years ago and who were so small that they could fit in the hand help scientists get into learn more about the evolution of the human brain.
In a study published yesterday in the journal Progress of scienceChinese and American researchers have used high-resolution imaging to examine the only known fossilized skull of Chilecebus, an extinct New World monkey, crawling around ancient mountain forests, feeding on leaves and mosses. fruits.
A key finding: primate brain size, long thought to have increased gradually over time, seems to have followed a more circuitous trajectory.
Primates are generally divided into two groups: the Old World, from which our own species originates, and the New World species from the Americas and Oceania.
"We are witnessing multiple episodes of brain expansion in each of these large groups, as well as to several episodes of actual reduction in brain size in certain groups," AFP said. John Flynn, co-author of the American Museum of Natural History.
The research, led by Xijun Ni, of the Chinese Academy of Sciences, used x-rays and CT scans of the interior of the Chilebus skull to determine its internal structure.
The fossilized skull was precisely dated because it was discovered among volcanic rocks. By placing the species in his larger family tree, the team was able to infer that brain enlargement was occurring repeatedly and independently in anthropoid evolution.
Although the chilecebus is about the size of a modern marmoset or tamarind, its brain had several grooves called "folds" that suggest a higher degree of cognitive complexity: In other words, the size of the brain is not always related to progression.
Moreover, in modern primates, the size of the visual and olfactory centers of the brain is inversely related, which means that species with an acute sense of sight usually have a weaker sense of smell, and vice versa.
But the researchers found that a small olfactory bulb at Chilecebus did not result in a stronger olfactory capacity, meaning that the two abilities are not coupled as previously thought.
Flynn said his research showed secrets that could be discovered from well-preserved ancient fossils.
"We can go to the mountains and make this remarkable discovery at 10,000 feet of altitude in the Andes and be able to enlighten us on the evolution of our history, to be able to test the previous hypotheses … (and) to be able to understand the evolution. of the complexity of the brain in primates.
"It's a really incredible opportunity to discover a truly well-preserved fossil." – AFP
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