Reciprocal Altruism Even though relatives may get preferential treatment, most people help out non-kin as well. What’s the reproductive advantage of helping someone who isn’t related to you? The most common answer is reciprocity. Through reciprocal altruism, helping someone else can be in your best interests because it increases the likelihood that you will be helped in return. If A helps B and B helps A, both A and B may increase their chances of survival and reproductive success. Over the course of evolution, therefore, individuals who engage in reciprocal altruism should survive and reproduce more than individuals who do not, thus enabling this kind of altruism to flourish.
Reciprocal altruism is evident across many species. A wide variety of animals groom each other. Large fish (such as groupers) allow small fish (such as wrasses) to swim in their mouths without eating them; the small fish get food for themselves and at the same time remove parasites from the larger fish. Rats share food with other rats who have shared with them. Wolves protect each other in fights against wolves from other packs. Frans de Waal (2019) has observed thousands of interactions among chimpanzees and seen how chimps who share with other chimps at one feeding are repaid by the other chimps at another feeding; those who are selfish are rebuffed, sometimes violently, at a later feeding. In addition, de Waal has observed more complicated forms of reciprocation. If Chimp A groomed Chimp B, for example, B became much more likely to then share his or her food with A. Similar types of behaviors among capuchin monkeys have also been recorded.