Reciprocal Altruism
A pattern in which an organism incurs a cost to help another now, in a way that only makes evolutionary sense if the favor is likely to be returned later. Vampire bats that share blood meals with roost-mates who have previously reciprocated are the classic field-documented case — the same shadow-of-the-future logic that sustains TIT FOR TAT in Axelrod's tournament, implemented through memory and social recognition instead of a computer program.