A theoretical approach that aims to explain all social or cultural phenomena in biological terms, denying them any causal autonomy. Twentieth-century incarnations of biological reductionism have relied to varying degrees on Darwin's theory of evolution and principles of natural selection. Within the human sciences, there have been attempts to explain observed differences in group behaviour—such as performance on intelligence tests, rates of mental illness, intergenerational poverty, male dominance or patriarchy, and propensity for crime—as being biologically determined, by claiming that groups have different biological capacities or evolutionary trajectories. The theories of Social Darwinism, eugenics, and sociobiology often involve biological reductionism. A recognition of the importance of biological conditions and human nature need not involve biological reductionism. See also ardrey.