Altruism
Handicap principle. Acts of altruism are often used to show others what skills one has and what resources one has access to. This may signal to others that the altruist could be valuable as a sexual partner. Women find altruistic men to be attractive partners. In animals, research has found that good hunters have better success finding partners to reproduce with. In humans, people who know that their acts will be seen sometimes even wastefully donate money they know are not needed by the recipient because it helps their reputation.