Every human embryo has a genital tubercle, which develops into a penis or a clitoris depending on the sex of the embryo. By 14 weeks, the genital tubercle has developed so that the male has an external phallus while the female phallus is internal. Differences in the male and female brain are not apparent until adolescence. The adult male responds to a much wider variety of erotic stimuli and experiences orgasm much more frequently than the female.