8.2a Biology Is Not Destiny

Scientific research across various disciplines, including sociology, biology, and psychology, does not support the widespread belief that gender differences are a result of biological factors. Contemporary research, for instance, shows that environmental factors significantly influence biology, shaping its function in specific environmental contexts.

Reviews of studies on the relationship between biology and sex category reveal tremendous biological variation related to sex among humans (Wade, 2013; Fuentes, 2025). Research has looked for links between genes, hormones, and brain components and sex and gender category and do not find these factors map onto a consistent sex binary. Instead, they find variation. This variation means that characteristics associated with male bodies are found in female bodies and vice versa.

Of course, researchers have discovered that some genes, such as those related to baldness, are linked to sex category, but genes are not destiny. While men more frequently become bald, women also experience baldness and hair thinning. Moreover, genes are unpredictable, and gene expression depends on their environment.

Hormones such as estrogens and testosterone are present in all human bodies and also depend on environment. Their levels and influence differ between bodies categorized as male and female. For instance, hormone levels fluctuate with age, reproductive state, and nutritional state (Fuentese, 2025). Moreover, hormone levels vary in response to environmental cues such as spending time with children (Wade, 2013). The brain also responds to and is shaped by the social environment, which helps explain why researchers have not been successful at “establishing simple correlations between brain differences and differences in behavior, skills, or interests” (Wade, 2013, p. 285).

Photo 8.5

Hormones In Children Are Very Similar

Children playing dress up… [Photograph]. FatCamera from Getty Images Signature via Canva Pro.

Overall, there are minor biological differences in genes, hormones, and brains. Still, the social and physical environment interacts with biological factors, suggesting that sweeping claims that biology is destiny are indefensible (Davis & Blake, 2018). Davis and Blake (2018, p. 115) conclude that it is the “social responses to biology,” rather than biology itself, that result in unequal social outcomes for men and women.