The intelligence that characterizes our species has allowed us to perform incredible feats never before seen in the animal world: build civilizations, use language, create very broad social networks, have consciousness and even be able to (almost) read minds.
However, there are reasons to think that The fact of having a privileged brain has cost us dearly
From the point of view of biology, intelligence has a price. And it is also a price that in certain situations could be very expensive. The use of technology and the taking advantage of the knowledge handed down by past generations can make us forget about this and, however, since Darwin included us in the evolutionary tree and as science unravels the relationship between the brain and our behavior, the border that separates us from the rest of the animals has been collapsing. Through its rubble a new problem is glimpsed.
Homo sapiens, as life forms subject to natural selection, have characteristics that can be useful, useless or harmful depending on the context. Isn’t intelligence, our main trait as human beings, one more characteristic? Is it possible that language, memory, the ability to plan… are just strategies that have been developed in our organism as a result of natural selection?
The answer to both questions is “yes.” Greater intelligence is based on drastic anatomical changes ; Our cognitive ability is not a gift granted by spirits, but is explained, at least in part, by drastic changes at the neuroanatomical level compared to our ancestors.
This idea, which was so difficult to admit in Darwin’s time, implies that even the use of our brain, a set of organs that seems so clearly advantageous to us in every way, can sometimes be a liability.
Of course, one could argue at length about whether the cognitive advances we have have caused more fortune or more pain. But, going to the simple and immediate, the main drawback of having a brain like ours is, in biological terms, its very high energy consumption
Energy consumption in the brain
Over the last few million years, the evolutionary line that goes from the extinction of our last common ancestor with chimpanzees to the appearance of our species has been characterized, among other things, by seeing how the brains of our ancestors getting bigger and bigger. With the appearance of the genus Homo, just over 2 million years ago, this size of the brain in proportion to the body rose sharply, and since then this set of organs has been enlarging over the millennia.
The result was that inside our head the number of neurons, glia and brain structures that were “freed” from having to dedicate themselves to such routine tasks as muscle control or maintaining vital signs increased greatly. This meant that they could dedicate themselves to processing the information already processed by other groups of neurons, making the thought of a primate have for the first time the “layers” of sufficient complexity to allow the emergence of abstract ideas the use of language, the creation of long-term strategies, and, ultimately, everything that we associate with the intellectual virtues of our species.
However, biological evolution is not something that in itself covers the price of these physical modifications in our nervous system. The existence of intelligent behavior, depending on the material base offered by that tangle of neurons inside our heads , needs that part of our body to be healthy and well maintained.
In order to maintain a functional brain, resources are needed, that is, energy… and it turns out that the brain is a very energetically expensive organ: Although it represents about 2% of the total weight of the body, it consumes more or less 20% of the energy used in rest state. In other apes contemporary to us, the size of the brain compared to the rest of the body is smaller and, of course, so is its consumption: on average, around 8% of the energy during rest. The energy factor is one of the main drawbacks related to the brain expansion necessary to achieve an intelligence similar to ours.
Who paid for brain expansion?
The energy needed to develop and maintain these new brains had to come from somewhere. The difficult thing is to know what changes in our body served to pay for this expansion of the brain.
Until recently, one of the explanations about what this compensation process consisted of was that of Leslie Aiello and Peter Wheeler.
According to Aiello and Wheeler’s “expensive tissue” hypothesis The greater energy demand produced by a larger brain also had to be compensated by a shortening of the gastrointestinal tract, another part of our body that is also very energetically expensive. Both the brain and the gut competed during an evolutionary period for insufficient resources, so one had to grow to the detriment of the other.
To maintain more complex brain machinery, our bipedal ancestors could not rely on the few vegetarian morsels available on the savannah; Rather, they needed a diet that included a significant amount of meat, a food rich in protein. At once, Stopping relying on plants at mealtime allowed the digestive system to shorten, with the consequent energy savings. Furthermore, it is very possible that the habit of hunting regularly was both a cause and a consequence of an improvement in general intelligence and the management of its corresponding energy consumption.
In short, according to this hypothesis, the appearance in nature of a brain like ours would be a clear example of a trade-off: the gain of one quality entails the loss of at least another quality. Natural selection is not impressed by the appearance of a brain like ours. His reaction is more like: “So you’ve chosen to play the intelligence card… well, let’s see how it goes from now on.”
However, Aiello and Wheeler’s hypothesis has lost its popularity over time, because the data on which it was based were not reliable It is currently considered that there is little evidence that the increase in the brain resulted in a compensation as clear as the reduction in the size of certain organs and that much of the loss of available energy was cushioned by the development of bipedalism. However, this change alone did not have to fully compensate for the sacrifice involved in using resources to maintain an expensive brain.
For some researchers, a portion of the cuts that were made for this are reflected in the diminishing strength of our ancestors and ourselves
The weakest primate
Although an adult chimpanzee rarely exceeds 170 cm in height and 80 kg, it is well known that no member of our species would be able to win a hand-to-hand fight with these animals. The weakest of these apes would be able to grab the average Homo sapiens by the ankle and mop the floor with him.
This is a fact that is referred to, for example, in the documentary Project Nim, which explains the story of a group of people who tried to raise a chimpanzee as if it were a human baby; Added to the difficulties in raising the ape was the dangerousness of his outbursts of anger, which could end in serious injuries with alarming ease.
This fact is not accidental, and has nothing to do with that simplistic view of nature according to which wild beasts are characterized by their strength. It is quite possible that this humiliating difference in the strength of each species is due to the development that our brain has undergone throughout its biological evolution
Furthermore, it seems that our brain has had to develop new ways of managing energy. In research whose results were published a couple of years ago in PLoS ONE, it was found that the metabolites used in various areas of our brain (that is, the molecules used by our body to intervene in the extraction of energy from other substances ) have evolved at a much faster rate than those of other primate species have. On the other hand, in the same research it was observed that, eliminating the factor of the difference in size between species, ours has half the strength of the rest of the non-extinct apes that were studied.
Increased brain energy consumption
Since we do not have the same body robustness as other large organisms, this greater consumption at the head level has to be constantly compensated by intelligent ways of finding energy resources using the entire body.
We therefore find ourselves in a dead end of evolution: we cannot stop looking for new ways to face the changing challenges of our environment if we do not want to perish. Paradoxically, We depend on the ability to plan and imagine provided by the same organ that has stolen our strength
