Our Evolutionary Inheritance

Hominization, or The History of the Human Lineage

Why You Can Have No More Than About 150 Real Friends

All of us know our recent personal histories and can say what we did this morning or last year. But typically, we know very little about our ancient history, when the human brain was developing. Yet this ancient history of our brains has at least as important an effect on our behaviour. It is this history, of the brains that preceded our own — those of animals and of the first human beings — that evolutionary science in general and evolutionary psychology in particular explore, in an attempt to help us understand ourselves better.

An adaptation is a trait that developed in the course of evolution as a result of the mechanism of natural or sexual selection. Adaptations are thus transmitted genetically and can be not only anatomical but also psychological. In the case of psychological adaptations, the selected genes help to lay down specific circuits in the brain. Thus the behaviours that contribute the most to successful reproduction will be selected.

EVOLUTIONARY PSYCHOLOGY

Evolutionary psychology is an approach that attempts to answer complex questions such as why we fall in love, why we place so much stress on beauty, why we want to have children, why so many people are unfaithful to their spouses, and why there is so much conflict and injustice in the world.

Evolutionary psychology is not a sub-discipline of psychology. It is a way of approaching the questions of psychology from the special perspective of evolution. This approach is justified because the nervous system that generates our individual behaviours is the product not only of our personal history but also, and most of all, of the evolutionary history of our species.

The human species did not evolve in modern cities or even in villages. An estimated 99% of the evolutionary history of Homo sapiens took place in an environment resembling today's African savannah. Throughout this period of over 2 million years, our ancestors lived in small nomadic groups of hunter-gatherers. It was only 10 000 years ago that some of them started to become sedentary and to practice agriculture.

Naturally, evolutionary psychologists do recognize that all individuals develop their own personal preferences and abilities in the course of their lives. But according to evolutionary psychology, behind these personal attributes lie certain universal attitudes that are found in all cultures. This “human nature” is the result of the long process of hominization that has led to human beings as we now know them.

Throughout their evolution, the ancestors of today's human beings must have very often encountered venomous animals, such as snakes and spiders, in their natural environment. Those humans who were more afraid of such animals or had a spontaneous aversion for them probably received fewer fatal bites and therefore probably reproduced more than those who were braver . As a result, they passed their healthy fear of snakes and spiders down to their descendants. In contrast, many people have been killed by automobiles, but since automobiles have been around for only about a hundred years, not enough time has passed for any special evolutionary selection to take place. Thus, we continue to have a fear of snakes and spiders that no longer represent any real threat to us, while we feel no such fear of automobiles, even though they cause thousands of deaths each year. Thus we see a good example of how evolutionary psychology can shed light on a universal behaviour: by looking not at our current environment , but rather at the environment in which almost all of our ancestors lived. Thus, in a sense, inside our modern skulls we still have Stone Age brains.

THE CRITIQUE OF EVOLUTIONARY PSYCHOLOGY

Evolutionary psychology holds that we can immediately deduce a certain number of effects of evolution on the way our minds operate. Evolutionary psychologists see natural selection as having exerted a preponderant influence over our cognitive faculties in the process of hominization. But this view has been criticized by some neurobiologists. Their critique begins with the difficulty of determining exactly how our ancestors lived.

Was our ancestors’environment really the way we think it was?

Next, these neurobiologists ask whether focusing on the environment of the first human beings, as evolutionary psychology does, is sufficient to explain our current behaviours. These scientists suggest that it may be necessary to go further back in time and give equal attention to the evolutionary pressures that shaped the brain structures of all mammals, for example.

These critics also question the concept of specialized modules on which the logic of evolutionary psychology is based. Lastly, because it is hard to know anything for certain about our Paleolithic ancestors’ way of life, these critics suggest that the explanations that evolutionary psychology has developed about the selective pressures our ancestors faced may be only one of many possible sets of hypotheses.

Some serious criticisms have thus been levelled at the most active proponents of this evolutionary approach to psychology, primarily by people who study the actual circuits and chemistry of the brain. Without questioning the influence of evolution on the human mind, these critics warn against the classic excesses that can result from the hasty adoption of a new scientific paradigm.