Why Evolutionary Psychology is Wrong

One of the most pervasive and useful theories in the life sciences is the theory of evolution. According to this theory a species does not come into being out of nothing, rather it comes into being from another, similar species via a series of changes i.e. one species evolves from another. While the mechanism for change is contentious, an important aspect of the theory is the mechanism by which any one change succeeds over any other. This is dealt with by the principle of natural selection. According to natural selection (or survival of the fittest), changes persist where those changes yield an advantage to the survival of the species. And, according to evolution the mechanism for persistence is inheritance.

If we apply evolutionary principles to human behaviour we are invited to answer the questions (i) Did that person do what she did as a result of an underlying innate disposition? And (ii) Is there a survival advantage to be had from such behaviour?

It is tempting to think that if the answer to both questions is "yes", then we have made progress in explaining some aspect of human behaviour and we may even be able to predict future behaviour. Being able to explain and predict behaviour is useful to the psychologist.

While it would be useful if evolutionary principles could play a role in understanding human behaviour, in this essay I will show that in fact they cannot be so applied - for a variety of reasons.

Suppose we have an evolutionary hypothesis about some episode of behaviour, say crying. Our hypothesis may be (say) that crying entered the human repertoire because there was a survival advantage in a mothers being able to locate her child. There is no way to prove that this is the case. We can equally well come up with alternative hypothesis (crying keeps the mother awake and able to feed the child) or even counter hypothesis (crying advertises the presence of the child and could attract a predator). Certainly we can say it is true that crying allows a mother to locate her child, but that does not mean that crying entered the behavioural repertoire on the back of that benefit.

Since any such conjecture can have an equal claim on being an evolutionary truth, there is no advantage (no explanatory or predictive value) to be had from trying to frame the conjecture in evolutionary terms.

A key principle for evolutionary theory is that change in a species is selected for by the survival of those individuals in whom the change is manifest. But, clearly change may occur which has no net effect on survival and such a change would neither overwhelm nor disappear in a population. It would simply be present as part of natural variation. It may or may not be inherited by any evolving descendants of the population. So it is quite possible for a feature to be introduced into a species without having any impact on its survival chances. Since we can only conjecture when investigating evolutionary advantage, we cannot even say whether a feature originally gave evolutionary advantage.

A feature may have been introduced for an evolutionary reason which no longer holds sway, even one which we could have no inkling of. Similarly, a feature introduced without a selective advantage, may at some time later in the evolution of the species be seen to have an advantage - but it has never been selected for, and so evolution has nothing true to say about that feature.

An individuals conscious behaviour is a result of her beliefs and desires. A rational individual will tend to follow a logical pattern of behaviour based on those beliefs and desires. It is not obvious what kind of evolutionary hypothesis can break this kind of rational behaviour. Evolutionary conjecture might have something to say about, for example, the depth of short term memory involved in decision making - but then evolution would have it that the brain has evolved to be efficient to the point where rational thinking is efficient and free from evolutionary influence. So, although the depth of short term memory may be arrived at by evolutionary pressure, the rational behaviour of the individual using that memory in no way reflects any evolutionary selection.

In making evolutionary conjecture there is an assumption that any behaviour has been selected for, or at least that it has not been selected against. But this assumes that we are at a pinnacle of evolution. We have no reason to suppose this. We could equally well be on the verge of extinction, and who is to say which characteristic human behaviour will be the end of us?

In summary then, it would be useful to psychologists to be able to explain and predict human behaviour. On the face of it, the principle of natural selection provides an attractive way to explaining why humans behave the way they do. But on closer examination natural selection cannot in fact add anything to our conjecture about behaviour because we cannot prove "why", or even "that", a particular behaviour was selected for. Applying evolutionary principle is a red herring and only likely to give false comfort to hypotheses which lack substance and support.