More broadly, kin selection can be seen as a special case of trait groups. The interaction of specific traits in a population can yield tangible fitness benefits to an organism bearing that particular trait, yet don't require a reproductive reinforcement at every reproductive generation in order to promote survival of that group.

Imagine two possible traits within a species, which are mutually exclusive (an organism can only express one or the other of them). The ultimate output of these traits can be expressed as a behavioral strategy for evolutionary game theory (competing for abstract "fitness units"):

Group 1's rule: "In any interaction with a member of my species, cooperate if the expected slice of the fitness pie is 40 percent or greater -- otherwise defect." They'll help even for less than an even take, despite this putting them behind the other party.

Group 2's rule: "In any interaction with a member of my species, defect unless the expected slice of the pie is more than half." They'll cooperate if it benefits them preferentially, otherwise compete.

Five organisms gather together for a round of evolutionary game theory. Four are Group 2, one is Group 1. They each interact with all of the others one for iteration, and each time they must split the take of 10 fitness units.

At the end all the organisms of Group 2 have 6 fitness units each, because they refuse to cooperate with each other (no net benefit), but each one gets 60 percent of the stakes in their interaction with the Group 1 organism. The group 1 organism interacted every time, and so it winds up with 16 fitness units in all (four per encounter). It loses every individual play, but wins the game on points. The trait propagates in the species' population despite the loss.

Real organisms can easily find themselves acting as members of hundreds or even thousands of trait groups during their lifespans; moreover, trait groups can aggregate or disperse quite quickly in a complex lifeform, faster than reproductive cycles occur.