You come from a long line of successful procreators. Your ancestors were mainly great at one thing: becoming ancestors, i.e. living long enough to mate.
Sure, they had other skills. They may have been good at pottery, fishing, stargazing, geomancy, or bird identification. But one thing is clear: The main thing skill they possessed was reproducing.
How do I know? Because judging by the fact that you exist, that’s the one thing I’m sure they actually succeeded at. Out of (many of) their peers, they made it to that highest level of biological virtue–they had offspring. I don’t know whether they made great pots or not. I just know they made the people who made the people…who ended up making you.
Well, this straightforward fact, the fact that your inheritance consists primarily in the ability to produce heirs, is the basic insight behind evolutionary psychology. It predicts that a great deal of your behavior is explicable in terms of reproductive drives.
But what about stuff that bears no apparent relation to mating? What about musical tastes, greed, the persistent love in long-sexless aged marriages, homosexuality, patriotism, and the whole gamut of human values and behavior? How can these be traced back to your ancestor’s skill at attracting (and their tendency to be attracted to) mates?