Scientists have found out why the human brain is larger than that of monkeys

The human brain hides in itself secrets notsmaller than the universe. But the universe is infinite and expanding with acceleration, and the size of the brain can hardly be compared with the smallest asteroid that orbits between Mars and Jupiter. On average, the brain of a healthy person weighs between 1300 and 1400 grams, which is approximately 2% of the weight of the human body. Of course, in history there have been people whose brains weighed more or less, as in the case of Ivan Turgenev and Anatole France - the brain of the first weighed a little more than two kilograms, and the brain of the second barely reached 1000 grams. At the same time, both writers were smart and talented. Interestingly, the structure of the human brain is similar to the brain of other mammals, only it is much larger in relation to body size than the brain of any other animal. And recently British scientists have finally figured out why.

Scientists from the University of Cambridge managed to grow human and gorilla brain organelles and compare their early development.

Does size matter?

In relation to body size, the human brainis huge - it is about six times larger than that of other mammals and absorbs 20 percent of the body's energy needs. According to evolutionary theory, there must be a very good reason to create and maintain something so expensive. But what is she like? Did our ancestors need great mental abilities to find and store food, for example? Or, perhaps, the reason lies in the difficulties with communication with peers or, at all, in the work of genes?

In animals, the relationship between brain size and body size may be a more accurate indicator of intelligence. But with Homo Sapiens, everything is different.

In the past, scientists have tried to find an answer to these andother questions, mainly analyzing correlations, such as how brain size relates to the size of social groups in apes and our fossil ancestors. For example, in a 2018 study published in the journal Nature, Scottish scientists using computer simulations concluded that the greater the mental needs, the larger the brain.

The human brain is larger than that of a dolphin, chimpanzee, African lion, and other mammals.

But not all experts agree with this point of view.Some experts believe that the reason why we have such a large brain lies in the emergence of language. Others believe that genes and complex molecular processes play a role in the development of the human brain. The truth, as is often the case, is probably somewhere in between.

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Why do we need a big brain?

Dramatic difference between brain sizehuman and our closest living relative of chimpanzees can be traced back to the moment when sapiens separated from a common ancestor with chimpanzees and other apes. The results of a study recently published in the journal Cell show how exactly in the course of its development, the human brain became so large.

Scientists from the Laboratory of Molecular BiologyThe University of Cambridge collected neurons from gorillas, chimpanzees and humans and reprogrammed them to resemble embryonic cells, that is, induced pluripotent stem cells (IPSCs). These stem cells were later grown in brain organelleswhich are essentially tiny developing brains.

“We tricked these cells into thinking they were embryonic again,” lead author Madeline Lancaster told The Guardian.

At five weeks of age, the organelles of the human brain (left) are much larger than those of the gorilla (top right) and chimpanzee (bottom right).

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As the authors of the scientific work write, in two days it became clear to them that the organelles of the human brain have grown much larger than those of other monkeys - by five weeks, the brain organelles of Homo Sapiens were about twice as large, and their size reached about four millimeters in diameter.

The most striking thing, however, is that scientists managed to find a molecular switch previously unknown to science - the main element of which is a gene called ZEB2... It is he who controls the growth of the brain by activatingat a later stage than during similar processes in the brain of primates. This allows neurons in the human brain to divide more actively into adulthood and probably makes us who we are.

The biggest difference between us and other monkeys is how incredibly large our brains are.

This is interesting: Is the universe like a brain?

To make sure that really ZEB2responsible for brain growth, the researchers tried to artificially delay the activation of the ZEB2 gene in the cells of the gorilla's brain tissue and accelerate it in human neurons. As a result, the gorilla's brain tissue grew more than usual, while human tissue, on the contrary, grew more slowly. Scientists note that a relatively simple evolutionary change in the shape of cells can have serious consequences in the evolution of the brain.