The document summarizes some key biological factors involved in human sexuality. It discusses how sexual behavior in humans serves purposes beyond reproduction, shaped by both biological and cultural influences. While culture has powerful effects, biological factors related to sexual arousal and response remain fundamental to understanding human sexuality. It then describes the processes of sexual differentiation into male and female, including the roles of sex chromosomes and genes in developing either testes or ovaries which influence further physical and neurological sexual differentiation. Areas of overlap between male and female development are also noted.