sex differences in human physiology sex differences in human physiology sex differences in human physiology are distinctions of physiological characteristics associated with either male or female humans. these differences are caused by the effects of the different sex chromosome complement in males and females, and differential exposure to gonadal sex hormones during development. sexual dimorphism is a term for the phenotypic difference between males and females of the same species. for general sex differences in humans, see sex differences in humans. example of male and female anatomy from front and back. the process of meiosis and fertilization (with rare exceptions) results in a zygote with either two x chromosomes (an xx female) or one x and one y chromosome (an xy male) which then develops the typical female or male phenotype. physiological sex differences include discrete features such as the respective male and female reproductive systems, as well as average differences between males and females including size and strength, bodily proportions, hair distribution, breast differentiation, voice pitch, and brain size and structure. sex determination and differentiation the human y chromosome showing the sry gene. sry is a gene which regulates sexual differentiation.