The strange skull of ancient apes reveals the secret of how the primates' brains grow

In a study published in late August in the journal Science Advances, researchers in China and the United States used high-resolution images to examine the only known fossil skull. of the extinct Chilecebus - a new world monkey that roams the ancient mountain forest, eating its leaves and fruits.

Scientists have long thought that the primates 'brain size is always translating, growing over time, but this fact shows that the size of the primates' brains grows through winding steps. and independence in evolution.

Primate species are divided into two groups: Former world monkeys living in Africa and Asia; New world monkeys live in South America and Oceania.

A special fossil skull of Chilecebus carrascoenis, a 20 million year old primate from the Andes mountains of Chile.

Research co-author John Flynn of the American Museum of Natural History told AFP: "We found that in the main evolutionary branch, the majority of them tended to expand the skull and increase the size of the brain. but while there are certain groups going in the opposite direction, their brains tend to decrease in size. "

The study, led by Ni Xijun at the Chinese Academy of Sciences, used computerized tomography (CT) and X-ray scans on the inner part of the extinct Chilecebus skull fossils to determine the structure. inside the skull.

Scientists have long thought that the primates 'brain size is always translating, growing over time, but this fact shows that the size of the primates' brains grows through winding steps. and independence in evolution.

Although the Chilecebus species is nearly the size of a modern Marmoset or Squirrel lion, the opposite of the monkeys, the Chilecebus brain has some grooves called folds, which show the complexity. more cognitive complexity, in other words, brain size is not always related to brain progress and development.

Moreover, in modern primates, the size of the visual and olfactory centers of the brain is inversely proportional, meaning that stronger visual development species often have inferior sense of smell and vice versa. again

But the researchers found that a small olfactory region in Chilecebus did not provide a stronger visual ability, meaning that in the evolution of primates, the visual and olfactory systems were not involved. as tight as the previous assumptions.

Reconstructed images of Chilecebus carrascoenis, they are about the size of a Marmoset or modern Tamarin lion monkey (they are only the size of an adult's hand).

According to JohnFlynn, scientists can use well preserved fossils to test hypotheses that scientists have always mistakenly believe are true.

"Thanks to the well preserved ancient fossil specimen at an altitude of 10,000 feet (3,000 m) on the Andes, we can better understand our evolutionary history, and we can test out fake ones. previous theories as well as being able to understand the complex evolution of the brain in primates. "