The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila), some snakes, and some plants (Ginkgo). In this system, the sex of an individual is determined by a pair of sex chromosomes (gonosomes). Females typically have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males typically have two distinct sex chromosomes (XY), and are called the heterogametic sex. Exceptions to these generalisations happen in the cases of XX males or XY females, or other syndromes.
Moral laws are just as real as scientific laws, and when we willingly ignore them we do so at our own peril.