Neurochemical origin of man
The appearance of a person was associated with the level of dopamine
Sergey Vasiliev, Naked Science
The differences between the brains of humans and other primates have been studied for centuries, and the unusually large size of our brain is only the most obvious example of such differences. It is believed that they accumulated for millions of years, as soon as people began to develop their unique features, including walking upright, creating and using tools, and speech. According to a widespread hypothesis, structural and neurochemical changes of the brain took place in parallel, and only in the last stages, about 1.8 million years ago, an increase in its size began.
Mary Ann Raghanti and her colleagues from Kent State University in the USA received brain tissue samples from various zoos, medical and biobanks. In total, the scientists had brain tissues of 38 individuals of six primate species, including humans, chimpanzees, gorillas, capuchins, macaques and baboons, who died of natural causes. The results of their research are presented in an article published by the journal PNAS (A neurochemical hypothesis for the origin of hominids).
The authors prepared sections of the striatum, a structure located deep at the brain stem that regulates movement and participates in learning. The samples were stained with dyes that bind to various neurotransmitters that play an important role in prosocial behavior. In addition, measurements of the number of neurotransmitters in living primates were carried out.
The work showed that humans and other hominids (in this case, gorillas and chimpanzees) are distinguished by an increased content of serotonin, neuropeptide Y and, above all, dopamine in the striatum. At the same time, acetylcholine, which is involved in the regulation of hierarchical and territorial behavior, is found less in us than in the same gorillas and chimpanzees.
According to Raghanti, this combination "sets the key difference that sets humans apart from all other species." Scientists point to a similar work published by the journal Science in November 2017. It was shown that humans stand out among primates with a significantly more active dopaminergic system.
All this allows Raghanti and her colleagues to voice the "neurochemical hypothesis of the origin of hominids", in which sexual selection on the part of females contributed to the appearance of more numerous offspring in males who demonstrated less aggressive behavior and greater propensities to empathy, altruism and other manifestations of high sociality. Also, males who were able to cooperate better with each other ensured greater success for themselves.
The process can be described as the action of a positive feedback system: an increase in the activity of the dopaminergic system led to an increase in cooperative behavior, which, in turn, required large amounts of dopamine. It's possible that it all started more than 4.4 million years ago, with the Australopithecines, the forerunners of our genus. They were already distinguished by reduced canines, which cannot be demonstrated with such a threat, which is often shown even by chimpanzees, the closest monkeys to us.
Portal "Eternal youth" http://vechnayamolodost.ru