Evolutionary epidemiology and manic depression.

The reformulation of epidemiological prevalence rates as evolutionary frequency rates puts medical genetics within an explicit framework of Darwinian theory. Yet an enduring and still current assumption of genomic medicine is that genes associated with disease are necessarily maladapted. Indeed, it seems it could hardly be otherwise. However, evolutionary epidemiology has begun to uncover important and surprising counter-exemplary case-studies. Thus, the present aim is to first outline this emerging sub-discipline of 'evolutionary epidemiology'. Then, a major psychopathological syndrome--manic-depression--is examined in some detail within the purview of evolutionary epidemiology. Its medical genetics are those of an adaptive polymorphism in the human genome. Hence, genes associated with what is now a major public health problem accrued as they conferred selective advantage in phylogeny. Why should manic-depressive etiogenes have been selected? A preliminary anatomic-functional model, assembled from facts of human paleoneuropsychiatry, more adequately contextualises manic-depressive genomics and phenotypy. In this model, manic-depression finds its heuristic origins in a hierarchy of behavioural strategies stabilised in phylogeny and embedded at serial levels in the brain (Hawk-Dove ESS). A proportion of the population has variant genotypy which appears to have been favoured in social competition phylogenetically but express more pathogenic phenotypy in the current environment. The paper closes with a brief consideration of clinical practices and ethical issues as alternative considerations emerge with the syndrome recast in a more positive Darwinian light.