While humans were evolving in Africa, the climate cycled from wet to dry and back again, over and over. In evolutionary terms, it did so quickly, every 20,000 years.
This meant that we had to switch back and forth between living in well-watered forests where food was abundant, and living on dry savannah plains where food was scarce.
How did we adapt? Humans developed two mating strategies, one suited to the forest, the other to the savannah:
- Promiscuity for the forest: Promiscuous mating leads to more children, who can populate a rainy forest ecosystem where food is abundant.
- Exclusivity for the savannah: Exclusive mating produces fewer children, who won’t overpopulate a dry savannah ecosystem where food is scarce.
These two mating strategies can be seen among hunter gatherer peoples today. Forest-dwelling hunter-gatherer peoples favor mating with several people, while savannah dwellers emphasize pairing off with one.
Why, in resource-rich industrial societies, are all of us not inclined to mate promiscuously? It’s because our two mating strategies are genetically “hard-wired” within us, a legacy of our evolutionary past.
Because the human mating drive is too strong to be controlled by culture alone, our two mating strategies are directed by our genes. The genetic “wiring” for Muse/Centaur mating seems to be the default, while Nymph/Satyr genes evolved later.
Because our mating genes evolved in response to environmental changes, they probably have environmental triggers. That is, a pregnant woman’s body “tells” a fetus: The climate is wet and there’s plenty of food. If you have Nymph/Satyr genes, it’s okay to turn them on.
Because our mating genes had to persist through many generations, they probably work through dominant and recessive pairs, like the ones that make us left- or right-handed.
However our mating genes work, they involve Feminine and Masculine hormones. Higher levels of oxytocin increase men’s sexual desire, while higher levels of testosterone increase women’s promiscuity. That’s why moderate-testosterone Nymphs are naturally attracted to moderate-oxytocin Satyrs, and minimal-testosterone Muses are instinctively drawn to minimal-oxytocin Centaurs.