Victims of evolution
Why do we get fat so easily and quickly
Irina Ziganshina, Novye Izvestia
There is such a funny scientific theory proving that love is an evolutionary invention. They say that our distant ancestors – monkeys – have a different pelvic structure compared to the human one, narrower. So, when the monkeys began to slowly descend from the trees and take sticks in their hands – that is, to perform the first "human" actions, their brains began to develop and grow, and therefore the size of the skull also increased. So in order to give birth to large-headed babies, nature needed to increase the width of the pelvis in females.
But! Thus, they became less mobile, and from full-fledged members of the pack turned into dependents. They could no longer run away from the leopard with the same ease or jump on a branch when they saw a cobra. That is, they became like outcasts. And in order for the males not to abandon them, nature invented love – a kind of biochemical mechanism that binds them to the changed females...
I remembered it for this reason: it is generally believed that we get fat because we do not exercise enough and eat too much fast food. However, scientists have doubted this. They suggest that not only laziness and bad habits are to blame for the modern obesity epidemic, but also evolution, which has made us "fat primates".
We are fat primates. This is in a nutshell the meaning of the work of biologists from Duke University (Durham, North Carolina), published in the journal Genome Biology and Evolution (Swain-Lenz et al., Comparative analyses of chromatin landscape in white adipose tissue suggest humans may have less beigeing potential than other primates). The closest relatives of humans are chimpanzees: our DNA matches 99%. At the same time, there are no fat monkeys in nature, but a person, even if his body is bulging with muscles, has quite significant reserves of fat.
Judge for yourself: a perfectly healthy person consists of 14-31% fat, while in other primates this indicator does not exceed 9%. To understand how this happened, the team of researchers compared fat samples from humans, chimpanzees and rhesus monkeys - a slightly more distant, but also related to us species of monkeys. Using a method called ATAC-seq, the scientists scanned the genome of each species for differences in how their fat cell DNA is arranged. Usually, most of the DNA inside the cell is compressed into spirals and loops tightly wound around proteins. Only in some areas of DNA is there enough "air" so that they are available for the action of the cellular mechanism that turns genes on and off.
The researchers identified approximately 780 DNA sites that were available for such a "switch" in chimpanzees and macaques, and in humans they became too dense for this. While studying these areas, the team also noticed a repeating DNA fragment that helps convert fat from one cell type to another.
And then we remember the message about the benefits of coffee in turning white fat into brown. The fact is that not all fats are the same. There is a white fat that everyone knows – the one that makes up the "marble" in the steak and grows around our waist. On the other hand, there are fat cells called brown fat – they are able to burn calories, rather than store them to generate heat and keep us warm (therefore, there is a lot of brown fat in the body of animals that hibernate, as well as in newborns who need to avoid hypothermia to survive).
That's the reason why we get fat so easily: the regions of the genome that help turn white fat into brown work in chimpanzees, and in humans, at a certain stage of evolution, they were mostly "locked up". We almost lost the ability to convert white fat and began to store it. From an evolutionary point of view, it was not in vain. Humans, like chimpanzees, need fat to protect themselves from hunger, cold and to keep their vital organs at rest. And the first people needed fat reserves for another important reason – they needed an additional source of energy to feed the growing brain.
In the six to eight million years since humans and chimpanzees evolved apart, the human brain has roughly tripled in size. The chimpanzee's brain remained the same. The human brain consumes more energy than any other tissue in the body. Apparently, it was the transition to storing calories of white fat, instead of burning calories of brown fat, that gave our ancestors an advantage in survival.
Probably, in the future, scientists will be able to discover a group of genes that can be "turned on" and "turned off" by converting one fat into another. But it's too early to talk about it now: such processes are a little more complicated than flicking a switch.
So we will assume that we have already figured out the two main categories that distinguish a person from an animal. It remains only to deal with the category of "happiness"…
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