Sexual differentiation in humans Sexual differentiation in humans Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts, breasts, body hair, and plays a role in gender identification. The development of sexual differences begins with the XY sex-determination system that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between male and female humans from an undifferentiated zygote. Females have two X
Inclusive fitness in humans "biological theory and evidence" also more strongly support the "nurture" perspective than the "blood" perspective. Both Schneider and Holland argue that the earlier "blood" theory of kinship derived from an unwarranted extension of symbols and values from anthropologists' own cultures (see ethnocentrism). Inclusive fitness in humans Inclusive fitness in humans is the application of inclusive fitness theory to human social behaviour, relationships and cooperation. Inclusive fitness theory (and the related kin selection theory) are general theories in evolutionary biology that propose a method to understand the evolution of social behaviours in organisms. While various ideas related to these theories have