For ordinary mortals, altruism is a behavior that involves some type of personal surrender or sacrifice for the benefit of others, without expecting anything in return; something that seems to contradict Darwinian ideas of selfishness and the selection of the strongest as engines of survival and evolution. Biologists, therefore, try to explain altruism considering that it takes place above all within families, where the sacrifice of a relative (giving, for example, a kidney) helps the survival of another member of the same family.
