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Biological determinism, also known as genetic determinism^[1] or genetic reductionism,^[2] is the belief that human behaviour is 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.^[3] It has been associated with movements in science and society including eugenics, scientific racism, the debate around the heritability of IQ,^[4] the supposed biological basis for gender roles,^[5] and the sociobiology debate.

In 1892 August Weismann proposed in his germ plasm theory that heritable information is transmitted only via germ cells, which he thought contained determinants (genes). Francis Galton, supposing that undesirable traits such as club foot and criminality were inherited, advocated eugenics, aiming to prevent supposedly defective people from breeding. Samuel George Morton and 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 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.

Galton popularized the phrase nature and nurture, later often used to characterize the heated debate over whether genes or the environment determined human behavior. Scientists such as ecologists^[6] and behavioural geneticists^[7] now see it as obvious that both factors are essential, and that they are intertwined.^[8]

Late in the 20th century, the determinism of gender roles was debated by geneticists and others. Biologists such as John Money and Anke Ehrhardt attempted to describe femininity and homosexuality according to then-current social standards; against this, the evolutionary biologist Richard Lewontin and others argued that clothing and other preferences vary in different societies. The biologist E. O. Wilson founded the discipline of sociobiology, founded on observations of animals such as social insects, controversially suggesting that its explanations of social behaviour might apply to humans.

History

Roots

Biological determinism dates back to the 1800s, but Stephen Jay Gould has spent his career tracing the roots of this “western” thought. Gould suggests that the main theories of biological determinism is based on bad biology and bad use of the scientific method. He presents three key ideas that have influenced biological determinism. The first is that measurement and quantification has changed science over the past century and without context, these measurements are useless. The second is that reinfication is valid because we put a name on it. The third problem is that the main thought behind biological determinism is that traits are inherited. Gould points out that various theories of biological determinism have no evidence or science to back them up, and even though these ideas are very flawed, people still widely accept them.^[9]

Germ plasm

In 1892, the Austrian biologist August Weismann proposed that multicellular organisms consist of two separate types of cell: somatic cells, which carry out the body's ordinary functions, and germ cells, which transmit heritable information. He called the material that carried the information, now identified as DNA, the germ plasm, and individual components of it, now called genes, determinants.^[10] Weismann argued that there is a one-way transfer of information from the germ cells to somatic cells, so that nothing acquired by the body during an organism's life can affect the germ plasm and the next generation. This effectively denied that Lamarckism (inheritance of acquired characteristics) was a possible mechanism of evolution.^[11] The modern equivalent of the theory, expressed at molecular rather than cellular level, is the central dogma of molecular biology.^[12]

Eugenics

The early eugenicist Francis Galton invented the term eugenics and popularized the phrase nature and nurture.^[13]

Early ideas of biological determinism centred on the inheritance of undesirable traits, whether physical such as club foot or cleft palate, or psychological such as alcoholism, bipolar disorder and criminality. The belief that such traits were inherited led to the desire to solve the problem with the eugenics movement, led by a follower of Darwin, Francis Galton (1822–1911), by forcibly reducing breeding by supposedly defective people. By the 1920s, many U.S. states brought in laws permitting the compulsory sterilization of people considered genetically unfit, including inmates of prisons and psychiatric hospitals. This was followed by similar laws in Germany, and throughout the Western world, in the 1930s.^[14][4][15]

Scientific racism

Under the influence of determinist beliefs, the American craniologist Samuel George Morton (1799–1851), and later the French anthropologist Paul Broca (1824–1880), attempted to measure the cranial capacities (internal skull volumes) of people of different skin colours, intending to show that whites were superior to the rest, with larger brains. All the supposed proofs from such studies were invalidated by methodological flaws. The results were used to justify slavery, and to oppose women's suffrage.^[4]

Heritability of IQ

Alfred Binet (1857–1911) designed tests specifically to measure performance, not innate ability. From the late 19th century, the American school, led by researchers such as H. H. Goddard (1866–1957), Lewis Terman (1877–1956), and Robert Yerkes (1876–1956), transformed these tests into tools for measuring inherited mental ability. They attempted to measure people's intelligence with IQ tests, to demonstrate that the resulting scores were heritable, and so to conclude that people with white skin were superior to the rest. It proved impossible to design culture-independent tests and to carry out testing in a fair way given that people came from different backgrounds, or were newly arrived immigrants, or were illiterate. The results were used to oppose immigration of people from southern and eastern Europe to America.^[4]

Human gender roles

Lynda Birke argues in her 1992 book In Pursuit of Difference that biology explains sexual differences by the mechanisms of chromosomes, genetics, and inheritance.^[16] However, hormonal differences are not absolute,^[17] and people can be born with intersex characteristics, for example as a genetic mosaic.^[18]Homosexuality can be attributed to both biological and social causes.^[19][20]Dean Hamer has studied the so-called "gay gene". The neuroscientist Simon LeVay in 1991 studied the difference in hypothalamic structures between homosexual and heterosexual men, finding that the INAH-3 suggested a partial cause for homosexuality.^[21][22]Richard Lewontin, Steven Rose, and Leon Kamin's book Not in Our Genes discussed a study of girls who were relatively "masculinized". The biologists John Money and Anke Ehrhardt looked for ways to describe femininity that fitted their own social standards, such as clothing preference or using makeup. The experiment, in Lewontin's words, "ignores the existence of societies in which women wear pants, or in which men wear skirts, or in which men enjoy and appropriate jewelry to themselves." Gender differences in work are becoming less pronounced, suggesting that these are imposed by society.^[5] In contrast, the standard model of sex and gender indicates a clear-cut dichotomy between males and females, with no overlap, a cultural model followed by professionals such as doctors when they deal with gender assignment.^[23]

Sociobiology

E. O. Wilson reignited debate on biological determinism with his 1975 book Sociobiology: The New Synthesis.