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Evolution and psychiatry

Hounslow & Spelthorne Community & Mental Health NHS Trust, Mental Health Services for Older People, Fordbridge, Holloway Unit, Ashford Hospital Site, London Road, Ashford, Middlesex TW15 3AA

Abed's (2000) enthusiastic advocacy of evolutionary psychology contains much that is sensible but its central hypothesis that psychiatry is weak because of its conceptual pluralism is unsatisfactory. Conceptual pluralism may be a sign of weakness but it is hardly unique to psychiatry. Abed's example of a physicist not violating the Newtonian law of gravity is particularly unfortunate. Einstein's general theory falsified the Newtonian theory of gravity nearly 100 years ago, but physicists still use the Newtonian theory when it is useful. Indeed modern physics abounds with mutually incompatible theories, and the mutually incompatible corpuscular and wave theories of light have been jostling side by side for a couple of centuries. If physics, the fundamental science, tolerates conceptual pluralism, then the other sciences, which are based on the laws of physics, cannot be criticised too severely for also being pluralistic.

This has led some philosophers of science to suggest that it is unrealistic for science to aim at the truth; rather, the purpose of scientific hypotheses is to provide a theoretical framework to help us overcome problems that we encounter in nature — the instrumentalist view (van Fraassen 1980; Churchland & Hooker, 1985). This instrumentalist view of science is less ambitious, but given the history of science seems more practical and persuasive. We should not, therefore, be too embarrassed by the conceptual pluralism of psychiatry — we are in good company.

EDITED BY MATTHEW HOTOPF

REFERENCES

Abed, R. T. (2000) Psychiatry and Darwinism. Time to reconsider? British Journal of Psychiatry, 77, 1-3.

Churchland, P. M. & Hooker, C. A. (eds) (1985) Images of Science. Essays on Realism and Empiricism with a Reply. Bas C. van Fraassen. Chicago, IL: University of Chicago Press.

van Fraassen, B. (1980) The Scientific Image. Oxford: Clarendon Press.

Author's reply

Rotherham District General Hospital, Rotherham S60 2UD

EDITED BY MATTHEW HOTOPF

I did not mean to suggest that a mother is always certain of the paternity of her offspring - merely that she is certain that her offspring perpetuate her genes, while a father can never be similarly sure that his genes are perpetuated in the off-spring of his sexual partners. Hence, it is suggested that each gender faced distinct reproductive problems that required different adaptive solutions.

I am indeed aware of the long-time opponents of evolutionary psychology that Lucas refers to. Most (e.g. Rose & Rose and Lewontin) are evolutionary biologists who are prepared to accept that physical organs (e.g. the eye or the hand) have been designed by selection but draw the line at the human psyche or mind. Their antipathy to any suggestion that the human mind may have any architecture whatsoever that could have been shaped by the evolutionary process places them effectively in the camp that views the mind as a tabula rasa.

Moreover, Lucas is quite mistaken in suggesting that evolutionary psychology is biologically deterministic. Biological determinism is simply wrong and you will find every book or chapter on the subject stressing this fact (see Buss, 1999; Thornhill & Palmer, 2000). Unlike the narrow (non-evolutionary) biological view, evolutionary psychology accepts that all traits are the result of the interaction of genes and the environment. However, the difference between this view and that of the ‘standard social science model’ (Tooby & Cosmides, 1992; Gaulin & McBurney, 2001) is that traits are not considered to be endlessly malleable. Some traits are fixed through a wide range of environmental conditions (obligate traits; e.g. having two eyes), while others are highly sensitive to environmental change (facultative traits; e.g. degree of tanning of the skin or the propensity to violence). Nevertheless, even obligate traits can be disrupted as a result of environmental factors at critical developmental stages.

Evolutionary psychology has no problem accepting complexity and contrary to Lucas does not consider the brain or any other human organ to be optimally designed. Evolution produces its effect quite often through compromise and through building on what already exists. The design of the human throat that creates the propensity to choke each time we swallow due to the passage of all the food precariously over the wind-pipe is a case in point. Nor is it denied that factors other than selection, such as drift and mutation, influence the frequency of traits in a given population. However, only selection is capable of producing adaptations - the domain-specific, highly specialised traits or organs that perform a survival or reproductive function for the organism and contribute directly to its inclusive fitness (see Williams, 1966). Hence, whereas the colour of blood may be the result of drift, the design of the lens in the human eye can only have been the result of selection.

Lucas alludes more than once to the excesses of ‘eugenics’ and ‘social Darwinism’. No doubt social Darwinism was bad science and an abuse of Darwinism. Evolutionary psychology, by contrast, is a hypothesis-driven empirical science and not a political ideology. This does not mean it cannot be abused or distorted but science cannot be blamed for its abuse by the unscrupulous. It is also worth remembering that the excesses of extreme ‘environmentalism’ (a trend still quite influential and prevalent in various quarters) were no less gruesome and led to the death of millions of people in Stalinist Russia and elsewhere all in the name of creating the new citizens (through re-education and indoctrination).

Finally, Prothero is right to point out that sciences other than psychiatry tolerate a degree of conceptual pluralism. However, I would contend that the pluralism in physics has stimulated considerable theoretical and experimental work to resolve the inconsistencies generated by mutually exclusive theories. Can we say the same about psychiatry?

REFERENCES

Buss, D. (1999) Evolutionary Psychology: The New Science of the Mind. Boston, MA: Allen and Bacon.

Gaulin, S. J. C. & McBurney, D. H. (2001) Psychology: An Evolutionary Approach. Upper Saddle River, NJ: Prentice Hall.

Thornhill, R. & Palmer, C. (2000) A Natural History of Rape: Biological Basis of Sexual Coercion. Cambridge, MA: MIT Press.

Tooby, J. & Cosmides, L. (1992) The psychological foundations of culture. In The Adapted Mind: Evolutionary Psychology and the Generation of Culture (eds J. H. Barkow, L. Cosmides & J. Tooby), pp 19-136. New York: Oxford University Press.

Williams, G. (1966) Adaptation and Natural Selection. Princeton, NJ: Princeton University Press.

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