Sex differences in humans
Sex 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 in females), and the external genitalia.A distinction is sometimes made between sex and gender. Sex differences generally refer to traits that are sexually dimorphic. Such differences are hypothesized to be products of the evolutionary process of sexual selection. By contrast, the term gender differences refers to average group differences between males and females that are presumably based on sexually monomorphic (the same between the sexes) biological adaptations.