In other words, we humans have large brains and are capable of moral thinking of the form, "It would feel good, but it is wrong", because millions of years ago, some of our ancestral groups innovated by thinking, "Masturbation feels good, but I'd better not".

Those groups which did not discover that masturbation is a bad idea remained "animals". The groups that did make this innovation generalized this new kind of thinking into what eventually became what we call "moral rules", which enabled the development of complex roles and social organizations, all of which both requiring and stimulating the enlargement of the brain and development of abstract cognition. The human species, and all of what we think distinguishes us from the other primates and animals, exists because millions of years ago we ate bananas, which caused our arms to lengthen, which caused our sexual reproduction system to "short circuit"!