Our brain is one of our most complex and important organs, as well as one of those that later on to finish developing (and that without taking into account that throughout our life we do not stop creating synaptic connections). It is a structure present in a large majority of animals and that has been developing in different ways and evolving in different ways according to the species over millions of years.
Focusing again on the human being, little by little have emerged in our ancestors different structures and capabilities as evolution continued its course, being currently the brain of our species the last of the genus Homo that remains alive. In this article we are going to try to get closer to what the evolution of the human brain has been up to today.
I recommend you to watch the following documentary abut this topic:
The evolution of the human brain
Analyzing what was the brain of our already extinct ancestors is an arduous 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.
The main problem relies on determining how the brain of the human being has evolved: the brain is soft tissue, which does not fossilize and ends up rotting and disappearing. This implies that, with the possible exception of subjects that died frozen and that had been preserved in the ice, the observation of a hominid brain is not possible directly.
This does not imply that evaluating 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 should have been based on the analysis of the endocranial structure.
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 certain 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 possessed.
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, it would take much more energy 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 intracranial orifices that allow the passage of blood vessels through it.
The development of the encephalon in the different hominin species
Mainly based on the cranial capacity and its morphology, we will try to approximate how the brain of the human being has evolved throughout evolution and in some of the most representative and known species of the group of hominins, formed by the bonobos, the chimpanzees, our bipedal ancestors and we, the sapiens. It should be noted that many of the following conclusions are merely hypothetical, debatable and subject to multiple inferences.
The ardipithecus is probably one of the oldest ancestors of the human being ever found, although the Aahelanthropus tchadensis (on which there is disagreement between them 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, of simian characteristics, possessed a small skull of approximately 350 cubic cm (the one of the present chimpanzees oscillates between the 275 and the 500).
This species was already bipedal, but its small encephalon makes the vast majority of superior cognitive abilities at best improbable. The fact that they lived collectively indicates a certain level of socialization, similar to the family groups of other great apes.
The knowledge of this species and its capabilities is limited.
Australopithecus are a genus of hominid 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 afarensis. This species was characterized by a cranium with a relatively small cranial capacity, around 400-480 cubic cm (not being larger in size than that of a large number of chimpanzees, although in size in proportion to the body it would be somewhat larger). The inside 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 capacities and its ability to reason and planning rather limited compared to a current human being. Neither did he possess an excessively large parietal lobe, the existence of developed brain areas that would allow complex oral language and not possessing a high level of creativity or memory was not likely. Apparently the dorsal part of the skull was larger, something that is linked to the processing capacity of visual perception.
Homo habilis was one of the first representatives of the homo genre. Homo habilis has a skull of larger size and something more rounded, with a cranial capacity of around 600-640 cubic cm.
It has been discovered that this species was capable of creating rough tools, which requires a certain planning skill and a frontal area development somewhat superior to the previous species. It also requires greater 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 bulge of the parts of the cranial vault corresponding to the areas of Broca and Wenicke is observed, not being unlikely the emergence of a very rudimentary form of language, strongly supported by gestures and visual communication in general. There is probably a higher level of blood supply to the brain.
The cranial volume of this species oscillates between 800 and 1000 cubic cm, this species being 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. The lengthening of the posterior part of the skull could indicate a greater development of the occipital, parietal and temporal lobes.
Neanderthal man is our closest extinct relative and in fact lived with our species for thousands of years.
The cranial capacity of the homo neanderthalensis could be even higher than ours, being able in its case to 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 his skull suggests a somewhat smaller frontal 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 took care of their patients, they probably had a language similar to ours and sometimes carried out burials, as well as dominating a type of relatively developed 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-consciousness.
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 most stand out in us and that allows us the realization and possession of superior cognitive functions such as reasoning or abstraction.
Also the artistic creation was considered long time exclusive of our species, although at present it is considered that the neandertales also could realize different cave paintings and ornamental elements. With regard to the consumption of energy and nutrients, 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 been increased sixfold compared to the first hominids.
However, our cranial capacity is lower compared to that of the Neandertals, with ours being between 1300 and 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 just on its size), we can not help thinking that perhaps previous or different species were much more capable of what was originally thought, being something to value in the future.