[Mossly]

Culture echoing biology.

Sexual reproduction evolves convergently from the fusion of similar gametes (isogamy) to those of dissimilar gametes (anisogamy).

Sexual differentiation produces dimorphic sexual asymmetry, a binary mating system of two types. Males produce many small gametes, females produce few large gametes.

Factored by the expensive cost of selection, copulation, gestation, and rearing, and females are naturally inclined to be more selective.

In a sellers market where everyone wants to buy, humans mate assortatively.

I highly recommend ‘The Evolution of Insect Mating Systems’ (1983) by Randy Thornhill and John Alcock. The diversity of insects provide excellent insight into the evolution of sexual reproduction.