Genetic conflicts, mental minefields

Anthony Stevens and John Price begin their book with a candid admission of the limitations of conventional psychiatry. They convincingly argue that psychiatric symptoms will never be fully understood unless you consider their evolutionary dimension. Stevens is a Jungian analyst and Price an ethologically minded psychiatrist. In its psychiatric aspects, the book is targeted mainly at mental health professionals, and draws on the American DSM IV and European ICD classifications of mental illnesses. As a contribution to evolution, the book sees itself as part of the now-fashionable field of evolutionary psychology.

Here Stevens and Price rush in where more experienced Darwinists fear to speculate. Randolph Nesse and George Williams recently published a book on Darwinian medicine that included a chapter devoted to psychiatry. Given that we know very little about the evolutionary basis of mental illness, their restraint was justified, and Stevens and Price's book only underlines the point.

The authors make their avowed task more difficult than it need be by their assumption that whatever has evolved must be "adaptive" in the sense of conferring some benefit on the organism. But, as Williams observed over 30 years ago, the principle of adaptation "should be used only as a last resort". Then, as now, "adaptation is often recognised in purely fortuitous effects, and natural selection is invoked to resolve problems that do not exist".

A case in point is homosexuality - obviously a difficulty even if you take Williams's view that reproductive success rather than adaptation is the bottom line for natural selection. Because females have two X chromosomes but males only one, natural selection will act twice as often on X genes that favour female reproductive success as opposed to male. Consequently, if genes appeared on the X that promoted women's fertility more than it reduced that of their close male relatives, natural selection could do nothing about it. What was adaptive for most women could be maladaptive for some men.

Again, the fact that the Y chromosome finds itself only in male bodies means that selection will act on its genes as if males were the only sex. This probably explains the recent finding that a gene critical to male reproductive success has migrated to the Y from chromosome 3. It would also explain why so many Y genes appear to have been disabled. The implications for psychiatry are not male and female "archetypes" of the kind imagined by Jung, but constitutional bisexuality and its resultant psychological conflicts discovered by Freud - and now explained by genetics.

The modern Darwinian view of evolution enshrined in the work of Williams and others is that natural selection is ultimately a question of genetic conflict, with genes competing for a place in the future by building bodies and brains that will carry them there, irrespective of the costs or conflicts that this may create in their carriers. Indeed, the recent discovery that maternal and paternal genes construct completely different parts of the brain and are at war during pregnancy and childhood suggests that psychological conflict is built into the human brain long before birth and expressed throughout life. Yet Stevens and Price fail even to mention insights into parent-offspring conflict that were published over 20 years ago. Instead, they perpetuate John Bowlby's outdated and discredited view of "the infant-mother archetypal system" as one of harmony, attachment and bonding, with conflict regarded as pathological rather than the norm we now know it to be.

Stevens and Price claim that "mental health results from the fulfilment of archetypal goals", and that "psychiatric symptoms are persistent exaggerations of adaptive psychological responses". They assume such responses are adaptive for the individual or even the social group as a whole. They fail to consider the possibility that those goals may be contradictory or that symptoms could be responses to genetic conflict within the individual, rather than adaptations to the external environment. Indeed, if the latest findings prove correct, it is conceivable that an evolutionary arms race between parental and sex chromosome genes for control of development and behaviour could have driven the exponential growth of the human brain and so may have laid the foundations for mental health and illness alike.

Christopher Badcock is reader in sociology, London School of Economics.