What is social life

Social life makes you smart

A brain is not essential for an organism to survive. Protozoa, plants and invertebrates have been able to manage without a brain for ages. It is different with "higher" animals. A brain is part of their basic equipment. "It forms the interface at which incoming stimuli from the outside world are converted into commands to activate the muscles, that is, into behavior," explains biology historian Thomas Junker. It took evolution around 650 million years to form the complex and powerful human brain from simple nervous systems such as those found in jellyfish or sea anemones.

It is true that the human brain, weighing around 1350 grams, is not the heaviest in the animal kingdom. The brain of elephants weighs around 5000 grams, and that of sperm whales as much as 8000 to 9000 grams. If, however, the body dimensions are included in the calculation, then humans have a considerably larger brain than one should expect based on their dimensions, writes the Bremen neurobiologist Gerhard Roth . "In humans, the brain is almost eight times, in dolphins five times and in chimpanzees two and a half times the size of the mammalian average." In all three species, the brain grew faster than the body in evolution. However, this happened fastest in humans, whose brain gained almost 1,000 grams in a few million years.

The question remains as to the causes of this enormous enlargement. It is undisputed that a powerful brain gave our ancestors advantages in the evolutionary struggle for survival. But what were these advantages? It is usually said that, thanks to their large brains, humans have developed an intelligence that is unique in the animal kingdom. This made it possible for him to survive even under adverse environmental conditions and in a world full of enemies. For a long time, the prevailing view among anthropologists was that the early development of the human brain came mainly under the pressure of the manufacture of new tools and weapons. Because their use allowed our ancestors to kill larger animals and use them as food. The additional energy gained in this way could be invested in a further enlargement of the brain, which in turn had a beneficial effect on the development of human intelligence.

Basically, this model can already be found in Friedrich Engels' unfinished work »The Part of Work in the Incarnation of the Ape«, in which work is primarily linked to the manufacture of tools: »Work first, after and then with it language - that are the two most essential impulses under the influence of which the brain of an ape has gradually changed into that of a human being, despite all the similarity, which is far larger and more perfect. "

There is no doubt that tool and weapon manufacture played an important role in the development of human technical intelligence. Nevertheless, many scientists today are of the opinion that the real driving force of human intelligence development is to be found in another field: the field of the social. The intelligence that developed here is also called Machiavellian intelligence - based on the Renaissance philosopher Niccolò Machiavelli, who in his 1513 work "Il Principe" ("The Prince") described the techniques of exercising power between states and people.

In short, Machiavellian intelligence describes the ability of a person to assert oneself in a social group against other group members. It is important for the individual to know who is pulling the strings in the group, who has become friends with whom or who are enemies, who can be trusted in an emergency. Those who are also able to empathize with the emotional state of others and assess their actions in advance gain additional advantages. In order to cope with all these tasks, a high level of brain power or intelligence is required. The forms of thinking that were first developed in solving social problems, claim the proponents of the theory of Machiavellian intelligence, later also proved to be suitable for understanding the laws of inanimate nature.

"If you take the size of a group as a rough indicator of social complexity and compare it with the proportion of the neocortex in the entire brain, there is actually a connection," says Junker. The neocortex is the genetically youngest part of the cerebral cortex, which is responsible for the more complex forms of information processing. The larger the social groups in which animals live, the higher the proportion of the neocortex in the total brain. "The intelligence of an animal obviously limits the maximum group size that can be achieved," says Junker. "If the group gets bigger, the individuals are no longer able to maintain social relationships and the group falls apart." According to this calculation, the maximum group size for chimpanzees would be 50 to 55 individuals, which agrees quite well with empirical observations. With humans, you get a maximum group size of 100 to 200 people. This corresponds to the average size of social groups among today's hunters and gatherers, for example in the Amazon region or Central Africa.

The question of which form of intelligence was of greater importance for the incarnation is controversial to this day, although more and more scientists are giving preference to social factors. An interesting discovery that also points in this direction has now been made by a team of anthropologists led by Mary Ann Raghanti from Kent State University in the US state of Ohio. After that, the "incarnation of the ape" was in all probability not accompanied by continuous growth of the brain. "Something changed before the brain got big, before we developed this enlarged cortex." The researchers suspect that changes in brain chemistry first took place, which in particular influenced the social behavior of our ancestors. Of course, such changes can no longer be proven today. Because of our ancestors who lived millions of years ago, fossil skull bones are at best left. Therefore, Raghanti and her colleagues examined the brains of recent primates, humans, chimpanzees, gorillas, baboons, macaques and capuchin monkeys. She paid particular attention to the so-called striatum, a region belonging to the basal ganglia of the cerebrum, which is significantly involved in the control of social behavior.

The researchers report on their results in the Proceedings of the National Academy of Sciences (DOI: 10.1073 / pnas.1719666115). Accordingly, the spectrum of different neurotransmitters in the brain shifted in such a way that in the development towards humans the aggressiveness was dampened and the willingness to cooperate was increased. In concrete terms, humans, chimpanzees and gorillas have higher serotonin and neuropeptide Y levels in the striatum compared to baboons and macaques. Both neurotransmitters are associated with an increased sensitivity to social signals. Humans, however, have significantly higher dopamine levels than great apes. In contrast, the values ​​for acetylcholine, a neurotransmitter associated with dominant and territorial behavior, are lower in humans.

The researchers emphasize that this combination of neurotransmitters is a striking difference between Homo sapiens and all other primates. "We assume that changes in the striatum triggered a reorganization of the brain, which at the same time facilitated the growth of the cerebral cortex." C. Owen Lovejoy, professor of evolutionary biology at Kent State University and co-author of the study, believes it is possible that the neurochemical changes began 4.4 million years ago. At that time a creature called Ardipithecus ramidus lived in Ethiopia, which anthropologists consider to be the earliest ancestors of man. Compared to chimpanzees, which have large canine teeth, which they often display aggressively, the canine teeth of the Ardipithecus ramidus males were reduced. "That is, when they smiled - like men do today - they probably signaled a collaboration," says Lovejoy.

The differences in brain chemistry may have triggered further evolutionary changes, including the development of mating behavior and language. According to the "neurochemical hypothesis about the origin of hominids" drafted by the US researchers, after the restructuring of the brain, more and more women mated with men who were reliable and less aggressive. This may have promoted social monogamy. At the same time, men who worked well with other men had more success in the hunt, in which they also shared the know-how for tool and weapon manufacture with each other. This in turn triggered another boost in the development of the brain and language.

Whether higher dopamine levels in the brain have actually changed human social behavior in the way described can currently only be speculated. It is also conceivable that the development of a dopamine-dominated striatum was merely the side effect of a different adaptation. The US researchers hope to gain new insights from an examination of the brains of chimpanzees and bonobos. While chimpanzees (pan troglodytes) often show aggressive and uncooperative behavior, bonobos (pan paniscus) are known for their peacefulness and their willingness to voluntarily share food with conspecifics. It seems likely that these differences are due to divergent dopamine and acetylcholine levels in the brains of both chimpanzee species. If such evidence were successful, it would undoubtedly support the new theory.

nd journalism from the left thrives on the commitment of its readers

In view of the experience of the corona pandemic, we have decided to make our journalism permanently freely accessible on our website and thus make it available to everyone who is interested.

As with our print and epaper editions, our work as an author, editor, technician or publishing employee is part of every published article. It is what makes this journalism possible.

Volunteer now with just a few clicks!