Closing the gender gap

Sex differences in humans, or gender differences in humans, have been studied in a variety of fields. In humans, biological sex is determined by five factors present at birth: the presence or absence of a Y chromosome, the type of gonads, the sex hormones, the internal reproductive anatomy (such as the uterus), and the external genitalia. Genetic sex is determined solely by the presence or absence of a Y chromosome. A child's presumed sex is determined at birth by observation of the external genitalia.