Our brain shrinks 50 times faster than we thought.

The shrinkage of the brain of modern humans is not new, the phenomenon was discovered as soon as we found enough hominid skulls and developed dating techniques (that is, to know in what time they lived), to realize that from 6 million years ago (the last time we and chimpanzees shared a common ancestor), cranial capacity (that is, the space that our brains occupy inside our skulls) has been increasing until it plateaued 70,000 years ago and then began a gradual decline that leaves us with us current humans with a deficit of 261 cubic centimeters compared to this skull from 40,000 years ago.

261 cubic centimeters is more than the volume of a cup, it is not little, if they take away a piece of brain of that size I suspect that you would not have a good time, but that is what happened, we have one less cup of Brain compared to humans 40,000 years ago, amazing!!

For 6 million years the size of the hominid brain quadrupled and seems to be directly related to an increase in intelligence, by the time they were already manufacturing specialized tools the brain of the Neanderthals exceeded 1,700 cubic centimeters and that of our primitive Homo Sapiens ancestor exceeded 1,500 cubic centimeters.

That's right, Neanderthals still hold the record for the largest brain among all hominids, including us, the relationship that seemed to exist for millions of years that the bigger the brain the more intelligent and sophisticated the hominid seemed to be stops around 70,000 years and reverses to leave us more intellectually developed humans with smaller brains (1300cc) than our ancestors.

The theories that have been devised to explain this phenomenon of shrinking brains are many, but the following two are the most popular:

The first is self domestication, as the name implies the reason our brains shrink is the same phenomenon seen in domesticated animals; The dog has a brain 29% smaller than that of a wolf, a pig has a brain 34% smaller than that of its wild counterpart, and a cow has a brain 25% smaller than that of its wild ancestor, extinct since 1627. huro, which like the wolf and wild pig was a larger version stronger and more aggressive than its domesticated variants.

This happens because being domesticated, being big, strong and aggressive, does not represent an advantage to survive, you do not have to be strong and aggressive to defend yourself from predators or compete with males of the same species to reproduce; the farmer gives you food, protects you from predators and decides whether or not to reproduce and with whom; to later be consumed.

Eliminating these evolutionary pressures, cunning and aggressive characteristics disappear generation after generation, so this theory says that our brain shrank because we domesticated ourselves, that our communities over the millennia found a way to eliminate those characteristics that they allowed us to survive in a more primitive environment, as we did by encouraging reactive violence within groups.

A person who is constantly violating the people around him is not good for the survival of the community and we have devised ways to get rid of them, some more macabre than others, this makes sense, but there is a very important against, we know that primitive humans and previous species already lived in similar groups with similar social structures and yet their brains continued to grow and that is why there is another theory.

The theory of size reduction: in this theory, the change in diet due to the invention of agriculture would have produced a nutritional deficit (it has been proven that today food has ~ 30% fewer nutrients) and consequently the reduction in size of individuals due to a caloric deficit would mainly affect the brain, which is an especially energy-demanding organ.

The brain consumes 20% of the calories we use, this makes a bit of sense because there is evidence, although not very conclusive, that the modern Human is smaller than the primitive Human, in the last 10,000 years we have lost about 5 kilograms of body mass on average, the problem with this theory is that in proportion that would explain a reduction in brain size of 22 cubic centimeters and not the 250 that we know we lost, so neither of these theories convincingly explains why we need a cup of brain.

What do you think, which theory is closer to the explanation of this phenomenon of reduction of the human brain, or will there be another one that is closer to the reality that we are going through. Leave it to me in the comments.

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