Selfish or Selfless On March 13, ..
Prosocial Behavior | Learning to Give
The question we are interested in is: which type will be favoured byselection? To make the analysis tractable, we make two simplifyingassumptions: that reproduction is asexual, and that type is perfectlyinherited, i.e., selfish (altruistic) organisms give rise to selfish(altruistic) offspring. Modulo these assumptions, the evolutionarydynamics can be determined very easily, simply by seeing whetherthe S or the A type has higher fitness, in theoverall population. The fitness of the Stype, W(S), is the weighted average of the payoff toan S when partnered with an S and the payoff toan S when partnered with an A, where the weights aredetermined by the probability of having the partner inquestion. Therefore,
Prosocial behavior is a type of voluntary ..
This simple model also highlights the point made previously, thatdonor-recipient correlation, rather than genetic relatedness, is thekey to the evolution of altruism. What is needed for altruism toevolve, in the model above, is for the probability of having a partnerof the same type as oneself to be sufficiently larger than theprobability of having a partner of opposite type; this ensures thatthe recipients of altruism have a greater than random chance of beingfellow altruists, i.e., donor-recipient correlation. Whether thiscorrelation arises because partners tend to be relatives, or becausealtruists are able to seek out other altruists and choose them aspartners, or for some other reason, makes no difference to theevolutionary dynamics, at least in this simple example.