I know that this is a contentious topic and I found conflicting explanations online which is what prompted me to put his question up. In some papers, Kin selection is mentioned based off the concept of inclusive fitness (sum of direct and indirect fitness). However, Kin selection is said to be an altruistic characteristic. That being said, altruistic genes only propagate through indirect selection (since an actor gives up its own fitness and do not generally reproduce). In that case, isn't Kin selection based off just indirect fitness and not inclusive fitness as a whole?

In a webpage, it is mentioned that "Kin selection is the evolutionary mechanism that selects for those behaviors that increase the inclusive fitness of the donor.". In that case, how can kin selection be altruistic? Can someone shed some light on what Kin selection is exactly? Also, a proper definition for indirect selection would be good as well. Thank you.


how can kin selection be altruistic?

Part of you confusion is purely semantic.

Kin selection cannot be altruistic. Kin selection is an evolutionary process. Altruism is a behaviour. Saying "kin selection is altruistic" is like saying "natural selection is flying" (when thinking of selection for flying abilities in, say, flying squirrels).


Altruism is a behaviour in which increases another individual fitness at the expense of its own fitness. However, this definition lead to confusion of whether one is talking to lifetime fitness or only to a contribution to one's fitness that will eventually be returned. For this reason people talk about True Altruism and False Altruism

True Altruism

True altruism is a behaviour in which the actors's (the one performing the altruistic behaviour) life time fitness is decreased while the recipient (the one benefitting from the altruistic behaviour) is increased.

True Altruism can only evolve via kin selection (or group selection for the few who still view these two processes as different).

It is the indirect component of the inclusive fitness that selects for altruism indeed.

False Altruism

False altruism refers to cases where the actor performs the behaviour because he is expecting (not necessarily consciously) a return later in life. False altruism can be seen as an investment.

Such false altruism can be selected by natural selection (no need to consider indirect fitness). "Return on investment" can be caused by direct reciprocity or indirect reciprocity. In case of indirect reciprocity, some populations can use a system of reputation, where individuals are more likely to help individuals that they have seen being helpful to others before.

Game theory

All types of interaction between individuals can be modelled in game theory. One can also investigate specific type of strategy in response to a a specific game. For example, Tit-for-Tat is one type of strategy in a multiple encounter between two individuals game.


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