In detail

The evolution of the human brain

The evolution of the human brain

The origin of our wonderful brain goes back millions of years ago and the growing need to meet the needs of humans.


  • 1 Origin of the human brain
  • 2 The mammalian brain: "A Revolutionary"
  • 3 The evolution of the brain

Origin of the human brain

The first fossils of an animal with a brain are about 500 million years ago. They are of a fish without jaws (the first vertebrates) with a pattern in its construction that will continue as a model throughout the evolution, from the lower vertebrates (fish, amphibians, and reptiles), following the upper vertebrates ( birds and mammals), until reaching man. He had a very difficult life during the Paleolithic. This model is constituted by the spinal cord followed by Brain stem, diencephalon and eventually the cerebral cortex.

This primitive brain has been followed as a model along the entire evolutionary scale, both in the anatomical diversity of brains found and in the brains of current fish. This diversity of brains seems to be due to the fact that based on that basic and fundamental pattern that we have indicated, “specializations” have been derived from it adapted to different ecological niches. Nevertheless, The bodily disadvantage of the human being compared to most animals is compensated by an invaluable organ: a large and complex brain.

Lateral cut of the brain

It has long distinguished the concepts of adaptation Y adaptability as inversely proportional. That is, the greater the adaptation of an animal to its environment, the lower the evolutionary talkative capacity it has in order to adapt to a new environment in the event that its original changes.

The evolutionary central line has always started with “non-specialized” brains, more undifferentiated and without particular developments of that basic pattern of that brain that we have already described.

The mammalian brain: "A Revolutionary"

Throughout the evolution of mammals, for more than 60 million years, brain development is considered a first and true revolution compared to the conservative process that had maintained this development until then. According to Jerison (1973):

“With this revolution, true intelligence is born, that is, the ability flexible to adopt for different response options before a given stimulus. This revolution is expressed in the first mammals with a  first and new organization of the brain, so that its larger size it is no longer done in a linear manner as in the primitive brains (lower vertebrates), but begins the contact or overlap of the posterior part of the cortex with the anterior cerebellum, and with it for the first time the exposure of the brain stem disappears, which is covered by these two structures ”

And the second great revolution of the brain is given by man, this is a fascinating process at the same time as surprising, as indicated by Tobias (1995):

“Man, in just a period of 2-3 million years, has increased the weight of the brain from 500 grams to 1,400 grams. An increase of almost a kilo of brain. Since the first data about the great hominoid primates were collected and cataloged as a single family under the name Australopithecus, the bridge between man and animals was established in a definitive way. The study of fossil remains allows us today to verify that from the ancestors of man, the Autralopithecines (Afarensis, average cerebral volume 400 cc; and Africanus 460 cc), the brain increased about 250-350 cc in Homo Habilis (700-750 cc of average cerebral volume). In Homo Erectus, the brain volume reached 900 cc, and hence its progression with Homo Sapiens until reaching 1,400 cc ”

After these tests just think and ask the big question:

What has happened so that in such a short space of time evolution has occurred so surprising phenomenon with the brain?

This is the most intriguing question about the evolution of the human brain. There is no doubt that the increase in brain size and organization in such a short time must have been the result of a series of processes in which a large number of factors have intervened.

Brain evolution

It would be wrong to believe that the evolution of the brain can be attributed to a single factor such as the acquisition of standing, the use and construction of tools, language acquisition or new ways of social life, such as agriculture and livestock. And even more importantly, there must have been “key” factors responsible for initially firing that accelerated race for the acquisition of a large brain.

The different human species had brains of different sizes that gave the human being the intelligence necessary to build substitutes for the lack of corporeal defenses, such as coats for the cold, weapons for defense and hunting or shelter rooms.

In hominids it is considered that the beginning of brain growth began about five or six million years ago in the specific context of a certain environment. This ecological niche was the encounter or limit between the humid jungle, and the dry and arid savanna. In this changing environment came the first adaptive changes of the brain in the ancestors of man. If so, it could be the ambient temperature in this savanna, along with primitive hunting methods, one of those “key” factors, not forgetting the great importance that must be given to the thumb of the hands that is opposable to all other fingers, thus developing the creativity of man and resulting in the creativity of man.

Luis Miguel Alcantara Velarde

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