The Evolution Of The Human Brain: How It Developed In Our Ancestors

This is how it is estimated that the brain of our bipedal ancestors changed.

Evolution of the human brain

Our brain is one of our most complex and important organs, as well as one of the later to finish developing (and this without taking into account that throughout our lives we do not stop creating synaptic connections).

It is a structure present in a great majority of animals and that has been developing in different ways and evolving in different ways depending on the species over millions of years.

Focusing again on the human being, little by little different structures and capacities have emerged in our ancestors as evolution followed its course, currently the brain of our species is the last of the genus Homo that remains alive. In this article we are going to try to get closer to how the human brain has evolved up to the present day.

The evolution of the human brain

Analyzing what the brain of our extinct ancestors was like is a difficult and complex task. In fact, a direct observation of an encephalon of species previous to ours (and even of ancestors within our same species) is not possible.

And the main problem in determining how the human brain has evolved is quite simple and at the same time extremely complex: the brain is soft tissue, so it does not fossilize and ends up rotting and disappearing. This implies that, with the possible exception of subjects who died frozen and were preserved in ice, the observation of a hominid brain is not possible directly.

This does not imply that assessing brain evolution is impossible, even if there is a science dedicated to it. We are talking about paleoneurology, which studies how the brain structure of our ancestors must have been based on the analysis of the endocranial structure.

Thus, in the same way that paleontology is a scientific discipline despite studying aspects of reality of which there are hardly any remains, in this case it is also possible to obtain scientific knowledge about organs that we can only know from what that surrounded them.

Paleoneurology

The main element that allows us to try to observe how the human brain has evolved is the cranial capacity, that is, the amount of brain volume that would fit inside a skull of a given species. Not only the size, but also the morphology can give us clues about more or less developed regions.

Another aspect to take into account, and which in fact is also linked to the emergence and progressive increase of intellectual capacity, is the level of blood supply that these brains possess.

A functional brain requires a constant energy supply, working better the more efficient the supply of oxygen and nutrients. And this means that at a higher level of cranial capacity and greater functionality of the brain, much more energy is required and therefore more blood to carry the basic nutrients to the brain. When we talk about fossils or bones, the simplest way to try to calculate the blood flow level of our ancestors is through the observation of the intracranial orifices that allow the passage of blood vessels through it.

The development of the brain in the different hominin species

Mainly based on the cranial capacity and its morphology, we are going to try to approximate how the human brain has evolved throughout evolution and in some of the most representative and known species of the hominin group, formed by the bonobos, chimpanzees, our bipedal ancestors, and us sapiens.

It should be noted that many of the following conclusions are purely hypothetical, debatable, and subject to multiple inferences.

On the other hand, it must be borne in mind that we still do not know well the evolutionary tree of our ancestors, since we only know it approximately from estimates (debatable and debated) about the position that each species occupies in the taxa of the evolution.

Ardipithecus ramidus

Ardipithecus is probably one of the oldest human ancestors ever found, although Aahelanthropus tchadensis (on which there is disagreement between whether it would be the first species of human or chimpanzee, and may even be the ancestor that distinguished both species) or the orrorin tugenensis are even older. This being, with simian characteristics, had a small skull of approximately 350 cubic cm (that of current chimpanzees ranges between 275 and 500).

This species was already bipedal, but its small brain makes the vast majority of higher cognitive abilities unlikely at best. The fact that they lived collectively indicates a certain level of socialization, similar to that of the family groups of other great apes today. Knowledge of this species and its capabilities is limited.

Australopithecus afarensis

Australopithecus are a genus of hominids related to us, being one of the first types of hominin that existed after ardipithecus.

Among the different existing species, one of the best known is the afarensis. This species was characterized by a skull with a relatively small cranial capacity, of around 400-480 cubic cm (not being larger in size than a large number of chimpanzees despite the fact that it would be somewhat larger in size in proportion to the body). The interior of the skull had different air cavities that protected the brain. There is a strong prognathism.

The morphology could reflect the existence of a relatively small frontal lobe, having few superior cognitive abilities and being its reasoning and planning capacity quite limited compared to a current human being. Nor did he have an excessively large parietal lobe, the existence of developed brain areas that would allow complex oral language was not likely, and he did not have a high level of creativity or memory. Apparently the dorsal part of the skull was larger, something that is linked to the ability to process visual perception.

Homo habilis

The Homo habilis was one of the first representatives of the genus Homo. Homo habilis has a larger and somewhat more rounded skull, with a cranial capacity of around 600-640 cubic cm.

This species has been found to be capable of creating crude tools, requiring some planning skill and somewhat superior frontal area development than previous species. It also requires more hand-eye coordination, with the motor area probably being somewhat larger. The fact that remains have been detected that indicate that they hunted also suggests the ability to generate strategies and an improvement in the level of communication.

The bulging of the parts of the cranial vault that correspond to the Broca and Wenicke areas is observed, the emergence of a very rudimentary form of language, strongly supported by gestures and visual communication in general, is not improbable. There is probably a higher level of blood supply to the brain.

Homo erectus

The cranial volume of this species ranges between 800 and 1000 cubic cm, being this species the one that began to dominate and use fire as a tool. They created tools and hunted cooperatively. Although to a lesser extent than later species, they probably had a somewhat more developed frontal lobe. Elongation of the posterior part of the skull could indicate further development of the occipital, parietal and temporal lobes.

Homo neanderthalensis

Neanderthal man is our closest extinct relative and in fact lived with our species for thousands of years.

The cranial capacity of homo neanderthalensis could be even higher than ours, and in his case it could reach between 1400 and 1900 cubic cm. This means that it is not known what level of abstraction they could reach. However, the morphology of its skull suggests a frontal somewhat smaller than that of sapiens, but in turn a larger size of the regions of the occipital lobe, dedicated to body self-control and perception.

It is known that they cared for their sick, probably had a language similar to ours and sometimes carried out burials, in addition to dominating a relatively developed type of lithic industry called the Mousterian lithic industry. All this implies that they had an area of ​​language and that they had the capacity for abstraction, empathy and a high degree of self-awareness.

Homo sapiens

Our species, which has traditionally been considered the most evolved and intelligent, is characterized at the brain level by an extensive development of the neocortex and especially by the enormous size of our frontal lobe. This is one of the elements that stand out the most in us and that allows us to carry out and possess higher cognitive functions such as reasoning or abstraction.

Artistic creation was also considered for a long time exclusive to our species, although at present it is considered that Neanderthals could also make different cave paintings and ornamental elements. When it comes to energy and nutrient consumption, it is estimated that our brain uses up to 20% of what we consume. It is also considered that the level of blood flow in our brain has increased six times compared to the first hominids.

However, our cranial capacity is smaller compared to that of Neanderthals, with ours being around 1300 to 1800 cubic cm. Although their greater cranial capacity does not mean that they had more or less intelligence (depending largely on the organization of the brain and not only on its size), we cannot help but reflect that perhaps earlier or different species were much more capable of what was originally thought, being something to value in the future.

Bibliographic references:

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  • Carotenuto, F .; Tsikaridze, N .; Rook, L .; Lordkipanidze, D .; Longo, L .; Condemi, S. & Raia, P. (2016). Venturing out safely: The biogeography of Homo erectus dispersal out of Africa. Journal of Human Evolution. 95. pp. 1 – 12.
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  • Seymour, RS; Bosioc, V. and Snelling, EP (2017). Fossil skulls reveal that blood flow rate to the brain increased faster than brain volume during human evolution. Royal Society Open Science.
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