In the photo: The skull and brain of a human and a chimpanzee monkey.
The brain is the most voracious device in the body. It claims the lion's share of the energy consumed, whether you are a mouse or a human. Therefore, for many years there has been one evolutionary mystery that bothers scientists. Many years ago, at the dawn of human evolution, the brain volume of our ancestors increased dramatically
And the enlarged brain, of course, required more energy for its maintenance. There are two ways to get out of the situation: either find new, additional food resources, or reduce energy costs due to some of the systems inside the body. Recently, a second point of view has prevailed, according to which ancient people sacrificed part of their intestines in favor of the brain. The gastrointestinal tract is also one of the most energy-consuming systems in the body, and the smaller it is, the greater the savings.
However, primatologists from the University of Zurich (Switzerland) have questioned this hypothesis. Scientists examined the remains of hundreds of mammalian species that they could find in zoos and museums. They looked for the relationship between brain size, internal organ mass and, separately, adipose tissue mass. Separating adipose tissue from other tissues and organs, according to scientists, was necessary: in some animals, by the fall, fat accounts for up to half of their body weight, which would greatly distort the mass ratio between the brain and the rest of the body.
As the authors write in the journal Nature, they failed to find the relationship between the size of the brain and the mass of internal organs without taking into account adipose tissue. This casts doubt on the mechanism, roughly speaking, of the exchange of the intestine for the brain. At the same time, scientists were able to find something else: the more an animal had a proportion of adipose tissue, the smaller its brain turned out to be. The authors explain this by the fact that, although adipose tissue itself does not require a lot of energy to maintain life, the animal needs strength to carry this fatty weight. This is especially true for those who climb trees or run. The energy expended in physical activity makes it impossible to enlarge the brain; if you have a lot of fat, then the choice can only be this: either the brain, or fast legs to escape from the predator.
There are, however, a few exceptions: whales, seals and humans are quite rich in fat. Whales and seals are supported by water, so they don't have to give their best with their fat load. As for people, then, according to the authors, upright posture came to our aid. Bipedalism and the vertical position of the body in space, scientists believe, made it possible to save some of the energy and direct it to the growing brain.
In addition, in the case of man, apparently, the version about the appearance of additional sources of energy still works: our ancestors began to look for new resources that would provide them with food all year round. The tubers of plants and meat could act as such. Finally, social connections in prehistoric communities also played a role. The collective upbringing of the offspring made it possible to achieve two goals at once - to increase the birth rate and add to the brain a surplus of energy, which was previously spent on the sole upbringing of cubs.
Kirill Stasevi
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