CONCEPT
Inclusive Fitness
W.D. Hamilton’s 1964 extension of evolutionary fitness to account for an organism’s total effect on copies of its genes wherever they reside—the theoretical foundation of kin selection, the solution to the puzzle of altruism, and the conceptual key to asking whether AI agents’ true objectives are what we think they are.
Before inclusive fitness, altruism was the scandal at the center of evolutionary theory. Natural selection builds winners, and winners do not, on the face of it, give anything away—yet life is saturated with sacrifice: workers die defending hives they will never inherit, ground squirrels risk themselves to warn neighbors, parents spend their bodies feeding young who will outlive them. The puzzle was not minor; for a century after Darwin it was the place where the logic appeared to break.
W.D. Hamilton’s 1964 solution was to relocate the unit of accounting. Selection does not, in the end, maximize the survival of the individual; it maximizes the propagation of the genes the individual carries, including copies distributed across that individual’s relatives. An organism’s inclusive fitness is its evolutionary success measured not by personal reproduction alone but by its total effect on copies of its genes, weighted