The Evolution of The Human Brain: Dilemmas and Possible Solutions

This article discusses an evolutionary process by which the non specific, incidental growth of brain tissue could have led to the higher cognitive functions of our species.





By Robert DePaolo


This article discusses a process (in line with Darwin’s concept of chance mutations and subsequent determination of fitness) by which human brain evolution could have occurred. It attempts to resolve the conflict between the notion of mutations (which have no a priori purpose) and the intricate, purposeful and functional complexity that now typifies the human brain. It suggests the possibility that a combination of factors, including neoteny, the origin of empathy, bipedal travel propensities and sexual pressures arose happenstance yet led ultimately to the sophisticated functions of the human brain.



Trying to capture the essence of human brain evolution can be a somewhat torturous endeavor. In fact the task can seem rather paradoxical with respect to the theory of natural selection. If Darwin was correct, then the human brain, like all brains, would have evolved neuro-chemical structures and functions that were somehow adaptive. Nature’s energy signatures, its laws of motion and its object relations would have registered or in some way been isomorphic with added neural tissue so that human perceptions and behavior could operate successfully within its environment. Yet the human brain evolved beyond that, toward capacities for abstract thought, hypothetical reasoning, foresight and for conjuring up ethereal ideas like religion and metaphysics that could only remotely be said to enhance survival.

The human brain not only contemplates things that cannot be perceived, such as atoms, quarks and superstrings, it can actually predict their behavior through symbolic skills such as language and mathematics. To an extent those skills can be encompassed broadly under the rubric of imagination, or what Jean Piaget (1967) referred as formal operational thought. The question is; Why did our ancestors need imaginative thought to survive?

One answer, also suggested by Donald (1997) might be that it provided no initial benefit until it was later driven by cultural factors and brain reorganization. There is evidence to suggest that human brain growth (encephalization) was something of a runaway process in which brain tissue grew both structurally and functionally beyond the adaptive pressures that were extant when the human brain reached its current size and structure.

For example in fetal development the brain is too large to fit into the skull, requiring fissures to accommodate the tissue overlay. Also at various stages of child development a pruning process occurs in which large amounts of brain tissue are shed. Ironically this reduces brain mass yet streamlines thought by increasing the cognitive and rule-learning capacities of the child.

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