The Raymond Pearl memorial lecture, 1997: The quest for medical normalcy-who needs it?

Darwinian natural selection is the only factor in evolution that maintains and improves adaptation. It does so by favoring genes that enhance the genetic success of their bearers under historically prevalent conditions, and need not favor health or happiness or conformity to some universally normal state. It may favor unpleasant departures from medical normalcy if they contribute to long-term genetic success, either directly or as unavoidable costs of features that make such contributions. It is also blind to future consequences of current evolution, so that every evolving lineage accumulates historical legacies that may seriously constrain future adaptation. Examples of adaptive but unpleasant abnormality are found in infectious diseases and other instances of conflict (between the sexes, between parent and offspring, between competitors for limited resources). Examples of unfortunate historical legacies are found in limitations on numbers of parts (limbs, sense organs) and in the tight human birth passage. Adaptation is a more useful medical concept than normalcy, but the purpose of medicine is not to facilitate natural selection or uncritically encourage biological adaptations. Medical intervention may legitimately promote human values by frustrating adaptations (e.g., by anesthesia) or by seeking the grossly abnormal (e.g., birth through the abdomen rather than the vagina). Am. J. Hum. Biol. 12:10-16, 2000. Copyright 2000 Wiley-Liss, Inc.