Biological determinism

Biological determinism, also known as genetic determinism,^[1] is the belief that human behaviour is directly controlled by an individual's genes or some component of their physiology, generally at the expense of the role of the environment, whether in embryonic development or in learning.^[2] Genetic reductionism is a similar concept, but it is distinct from genetic determinism in that the former refers to the level of understanding, while the latter refers to the supposedly causal role of genes.^[3] Biological determinism has been associated with movements in science and society including eugenics, scientific racism, and the debates around the heritability of IQ,^[4] the basis of sexual orientation,^[5] and sociobiology.^[6]

In 1892, the German evolutionary biologist August Weismann proposed in his germ plasm theory that heritable information is transmitted only via germ cells, which he thought contained determinants (genes). The English polymath Francis Galton, supposing that undesirable traits such as club foot and criminality were inherited, advocated eugenics, aiming to prevent supposedly defective people from breeding. The American physician Samuel George Morton and the French physician Paul Broca attempted to relate the cranial capacity (internal skull volume) to skin colour, intending to show that white people were superior. Other workers such as the American psychologists H. H. Goddard and Robert Yerkes attempted to measure people's intelligence and to show that the resulting scores were heritable, again to demonstrate the supposed superiority of people with white skin.^[4]

Galton popularized the phrase nature and nurture, later often used to characterize the heated debate over whether genes or the environment determined human behaviour. Scientists such as behavioural geneticists now see it as obvious that both factors are essential, and that they are intertwined, especially through the mechanisms of epigenetics.^[7][8] The American biologist E. O. Wilson, who founded the discipline of sociobiology based on observations of animals such as social insects, controversially suggested that its explanations of social behaviour might apply to humans.^[6]