There is a joke: the amount of intelligence on the planet is a constant value, and the population is growing all the time. But is this really a 100% joke? Or are we getting dumber? The fact is that over the past 25 thousand years, our brains have become smaller. Anthropologist Stanislav Drobyshevsky tells about this and the vicissitudes of human evolution in the next issue of our friends - Sci-One TV channel. Read the text version under the cut.
If we trace the evolution of the brain from Australopithecus, the first two-legged, to the present, it turns out:
- The growth of the brain was non-linear, bursts, faster, sometimes slower, sometimes decreasing.
- The size and shape did not change synchronously. As a rule, at first the size was slightly increased, then the shape changed. And even different parts of the brain did not change simultaneously.
We do not know all the details of this evolution, but its task was never to create large brains. Each subsequent change in structure, size, shape, function was a response to some external conditions. The environment changed, life set new tasks, the body gave new answers. And most often it turned out that the answer was in the form of even more wisdom. Apparently, to a large extent because not only people became smarter. If you look at the evolution of any animal, then cephalization - an increase in the brain - is characteristic of all. Therefore, since our ancestors did not live in a vacuum, they communicated with other beings. They hunted them, ran away from those who hunted them. And they had to do it better and better, because the other creatures ran away and hunted better and better. A person will never be able to run as fast as an antelope,and outwitting an antelope is possible. But here we need to grow wiser at a faster pace, which our ancestors did.
Sometimes the conditions turn out to be such that you can not only not get smart, but even get a little stupid. And there are at least two such examples in evolution. The first is the so-called Flores hobbits, ancient people who lived between 190 and 50 thousand years ago on the small island of Flores in Indonesia. Their ancestors got there about a million years ago, most likely from Java. They were the classic exemplary Javanese Pithecanthropus.
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Over the next several hundred thousand years, they drastically decreased in size. As the latest research shows, their brains began to weigh 420 grams or less. Moreover, the Pithecanthropus ancestors had a brain of about a kilogram. Of course, not like ours, but even a kilogram is not so little. This was quite enough to make stone tools, hunt animals, and so on in the same spirit, that is, they were quite human beings. And in Homo floresiensis, brains have reached the level of Australopithecus and modern chimpanzees.
At the same time, surprisingly, they did not stop making tools, which also decreased in size. The first tools on Flores were healthy cobblestones, stone choppers. In the hobbits, they turned into little flakes, because their paws were smaller. Hobbits hunted animals, the fauna there was very peculiar: giant half-meter rats, monitor lizards, stegodon dwarf elephants under two meters in height. But the hunters themselves were twice as low. And there were also giant storks, about 1.8 m high. With the growth of hobbits in a meter, this, in general, was impressive.
The life of these hobbits was not to say that it was very fabulous, because the same storks or monitor lizards were chasing them. But you don't need too much intelligence to run away from a monitor lizard or catch a rat. The elephant is probably more difficult, but, as architectural practice shows, the hobbits hunted young stegodons. Probably because they were still inexperienced. Or maybe they just found carcasses of dead elephants.
The second example of a brain shrinkage in the course of evolution is, oddly enough, ourselves. In the Upper Paleolithic era - from 40 to 25 thousand years ago - the average brain size of men was 1500 grams. And modern men already have 1400 grams. It is clear that this is the average value for the planet, and there is a fairly large variation from group to group, depending on the territory. In some groups, the brain size became even larger. For example, the Kazakhs, Buryats and Mongols have the largest brains today, even more than during the Paleolithic period. But on the whole, the dynamics of the planet is negative. 100 grams - the difference is not specific, but pretty decent. And a big acute question arises: why did this happen? Is the decrease in brain size a consequence of the fact that we have become more stupid, or has it gone with impunity?
There are two main points of view. The first is optimistic. According to this point of view, the brain has become smaller, but at the same time more complex at the level of the structure of neurons, synapses, neurotransmitter chemistry, etc., so we have become smarter. Indeed, practice shows that the intelligence of a modern person does not really depend on the size of the brain. A decrease in intelligence is observed with a brain mass of less than 700 grams. And everything that is more, no longer correlates with the degree of development of the mind. It is not the amount of nerve tissue that is more important, but the number of connections between neurons, the ability to transmit impulses, the speed of transmission, branching of dendrites, and much more. We are almost unaware of such details of the brain structure of Cro-Magnons, the first Sapiens. Therefore, the version that the brain has become more complex is currently unprovable. But, in principle, it is verifiable,because we know all the genetic information of ancient people. And if we knew how the formation of the brain is encoded in genes, we could assess its structure in the ancient Cro-Magnons. Unfortunately, no modern geneticist knows this.
The second point of view is that the biochemistry and neural structure of the Cro-Magnon brain was fundamentally the same as it is now. I share this opinion because not much time has passed from the point of view of evolution. If we compare Cro-Magnons with modern people in the structure of the face, hand, foot and spine, the differences will be barely noticeable, on the verge of statistical error. Most likely, the brain also changed slightly, except for its size.
Perhaps the 100-gram reduction made us individually a little dumber. We don't have to be as smart as Cro-Magnons. 25 thousand years ago, a Cro-Magnon had to learn how to make tools, light a fire, build a dwelling, hunt mammoths, saigas, zebras, kangaroos, anyone, in the first 10 years of his life, know poisonous and edible plants and mushrooms, how to escape from predators … And he had no right to make a mistake, because the groups did not have a large number of experienced people, there were no old people, there was no written language. The Cro-Magnon had to remember the first time and forever, and think very quickly in order to survive. The selection was tough. It was necessary not only to learn everything as soon as possible, but also to teach your children at the pace of a waltz.
Over time, life expectancy began to increase, grandmothers, grandfathers and writing appeared; crèches, kindergartens, schools and universities appeared; there was an opportunity to learn everything at any time. It is no longer necessary - and indeed impossible - to know everything in the world, each of us is familiar with only a small fragment of the universe. For example, I know how to talk about our ancestors, about our past and a little about the future, but I don’t know how to survive in the forest in winter. Like the vast majority of modern people. There are mega-survivalists, but they hardly know, for example, how their boots are made. Each person knows only a tiny piece of the mosaic, and no one can grasp the overall picture with the mind. But we, for our piece of the puzzle, do not need too many brains. And so it is quite possible to live. Even when a person is born with a small brain, and maybewith reduced abilities, then this is enough for him to do some specific business. And therefore, the gene pool of modern people over the past thousand years has been constantly diluted with the genes of the owners of not the most prominent brains.
If this trend continues - and the population grows, specialization intensifies - then the brain may shrink further. Even the hobbits with their 400 grams in their heads made tools. So the further evolution of our brain depends only on the conditions in which our descendants will live, what conditions they will create for themselves. So far, we are more successful in breaking our habitat, but I want to believe that we are not called Homo sapiens for nothing.
Successful evolution to all, and may science be with you!