Human mating is complicated, and studying it has neither made me more optimistic nor pessimistic. It is what it is. But if there’s one thing I’ve learned, it’s that the best lessons on mating don’t come from the evo psych of mating, but from the evo psych of cooperation. Romantic relationships are a kind of cooperative relationship, and the same lessons—not defecting in prisoners dilemmas, reciprocating, coordinating on focal points, dividing resources fairly, bargaining for better treatment, costly signaling—apply. So it might be better to ask the evo psych people who study cooperation. I think they’d have the most useful things to say on the topic.