Defeminization and masculinization are the processes that a fetus goes through to become a male. It has often been said by biologists that in sexual differentiation in mammals, the female is the "default" developmental pathway, in the sense that elimination of any of several gene actions necessary for formation of male genitalia leads to the development of external female genitalia (though development of functional ovaries requires effective action of several less understood sex-specific genes). Two processes: defeminization, and masculinization, are involved in producing male typical morphology and behavior. Disruption of either of these processes in males produces female-typical development. The opposite is not true, disruption of normal sexual development in females does not lead to mal