Beginning in the 1920s when the Franz Boas school of anthropology succeeded in decoupling the biological from the social sciences, Darwinism has been marginalized in the human sciences. Although early in the century William McDougall had proposed an "instinct" theory of personality, and G. Stanley Hall had advanced an evolutionary perspective for developmental psychology, Darwinism was swept away in the 1920s by various environmentalist doctrines. Freud's Oedipal theories and Watson's behavioral molding of individuals were compatible with Marx's assumptions of the malleability of entire social groups through government intervention.
In the 1950s, hostility to the record of Nazi racial atrocities tainted attempts to restore Darwinism to the social sciences. From that time on, it became increasingly difficult to suggest that individuals or groups might differ genetically in behavior without being accused of Nazi sympathies.
Those who believed in the biological identity of all people, on the other hand, remained free to write what they liked, without fear of vilification. In the intervening decades, the idea of a genetically based core of human nature on which individuals and groups might differ was consistently derogated. This intellectual movement has been politically fueled by successively coupling it to Third World decolonization, the U.S. civil rights movement, the struggle against apartheid in South Africa, and the renewed debates over immigration.
Let us be explicit about the problem faced by Darwinian psychology -- political correctness. Its central thesis is the environmental determinism of all important human traits. It stems from Marxism and a belief that social and economic oppression are the cause of all significant individual and group behavioral differences. The Marxist hold on liberal political sentiment is so extensive many of us think that way without realizing it. We censor ourselves lest we even dare to think the forbidden thoughts.
In a 1975 paper invited by the British Association for the Advancement of Science, Professor Hans Eysenck, himself a refugee from Hitler's Germany but a strong advocate of Darwinian bio-social psychology and the doyen of British psychology, wrote:
It used to be taken for granted that it was not only ethically right for scientists to make public their discoveries; it was regarded as their duty to do so. Secrecy, the withholding of information, and the refusal to communicate knowledge were rightly regarded as cardinal sins against the scientific ethos. This is true no more. In recent years it has been argued, more and more vociferously, that scientists should have regard for the social consequences of their discoveries, and of their pronouncements; if these consequences are undesirable, the research in the area involved should be terminated, and the results already achieved should not be publicized. The area which has seen most of this kind of argumentation is of course that concerned with inheritance of intelligence, and with racial differences in ability.
Richard Lynn, another British Darwinian psychologist, noted that many politically left-of-center scientists are currently in the same position as Christians were after the publication of The Origin of Species. He called on liberals to do what honest, intelligent Christians did then and what many still do today. Bite the bullet, and jettison those aspects of their world view (like egalitarianism) that are incompatible with the science of natural selection. Political correctness must be discarded if evolutionary theory is to achieve its full promise to become the unifying framework for the human sciences.