is promiscuity genetic or a result of environmental stimuli?

Does a woman's promiscuity and desire to do so generate from emotional well-being, "daddy issues", psychological or sexual trama, etc. Or is it a genetically predisposed attribute? SSRI's can decrease libido, so does that mean all women have the same sex drive genetically (such as all men seem to be on the sexual prowl constantly-evolutionarily to add as many copies of their genes as possible to the population) or does it change from brain chemistry? (obviously hormonal levels and sex drive have a flux during cyclic rhythms). Is promiscuity an evolutionary defense mechanism?