why do nouns have gender in some languages
Grammatical gender The division into genders usually correlates to some degree, at least for a certain set of nouns (such as those denoting humans), with some property or properties of the things that particular nouns denote. Such properties include animacy or inanimacy, "humanness" or non-humanness, and biological sex.
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), and the external genitalia.[1] 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.