A tiny 20-million-year-old skull sheds light on the evolution of the human brain

Scientists from the Chinese Academy of Sciences have completed the study of the skull of an ancient monkey of the species Chilecebus carrascoensis, which lived about 20 million years ago. It is believed that they may be one of the oldest human ancestors, since 36 million years ago this species separated from the common tree, from which most of the monkeys on the planet then came. Alas, in order to prove or disprove any theory, fossil specimens are needed, but they are practically not found. This skull is the only one found in the world since 1990.

The monkey Chilecebus carrascoensis was tiny, weighing less than half a kilogram, and could fit in the palm of a modern adult. But this is not of fundamental importance, on the contrary - scientists hoped with the help of the remains to prove that the size of the brain and the level of its development are not related. This could help to establish how the brain of animals developed before reaching the complexity of the human.

In fact, studying the monkey's brain left more questions than answers. With the help of computed tomography, scientists have obtained a three-dimensional model, on which the forms characteristic of a thinking creature are quite clearly traced. And he has a sufficiently developed optic nerve, which indicates the creature's daily lifestyle - it was guided by sight. But here's the problem - in Chilecebus, the optic and olfactory nerves are not balanced with each other.

Usually in animals there is a direct sensory dependence, when the lack of vision is compensated for by an excellent sense of smell and vice versa, but in the monkey Chilecebus carrascoensis everything is different. Scientists have hypothesized that vision, scent, hearing and other aspects of information processing developed independently of each other, in a mosaic manner. And the brain itself served as a compensating organ that processed the uneven flow of data and helped the animal make informed decisions, rather than relying on simple instincts.