Humans clearly attend closely to status, an important part of status is dominance, and a key way we show dominance is to tell others what to do. Whoever gets to tell someone else what to do is dominating, and affirming their own status. But we are also clearly built to not notice most of our status moves, and so we attribute them to other motives. And as long as we are making up motives, we might as well make up the most admired of motives, altruism.

Of course, that is Robin Hanson. Of course, you should read the whole thing.