Individualism is a modern luxury. It seems to me that for large swathes of our evolutionary history, being too selfish could you get killed directly, or indirectly through excommunication from the tribe. I'm not sure what the implication is to the present. Perhaps we have latent psychophysiological potential for decreased selfishness due to selective pressures. I don't think we understand the degree to which the apparent characteristics of human nature are actively modulated by environment.