“The evolution of indiscriminate altruism in a cooperatively breeding mammal”
Chris Duncan, David Gaynor, Tim Clutton-Brock, and Mark Dyble (June 2019)
Why do animals cooperate? One of the most powerful explanations for the evolution of cooperation is kin selection theory, which suggests that altruism may evolve when cooperative behaviors are directed towards genetic relatives. Meerkats, a species of cooperatively breeding mongoose, exhibit a wide range of cooperative behaviors; they babysit and feed the newly born pups of other individuals, look out for predators, and work to maintain hiding holes and sleeping burrows for the group. In this paper, researchers from the University of Cambridge analyzed data from a long-term study of meerkats in the Southern Kalahari Desert, South Africa. They find that although meerkat helpers cooperate extensively, individual helpers do not appear to provide more assistance to more closely related kin – they are indiscriminate altruists. Why is this the case? The researchers hypothesize that in groups of high genetic relatedness (as seen in meerkats), natural selection could favor indiscriminate altruism over kin-discriminate altruism if individuals frequently make mistakes in estimating their relatedness to group mates. However, in groups of lower genetic relatedness (such as humans), indiscriminate altruism is unlikely to evolve, even when kin-recognition is prone to substantial error. This provides an explanation for both the evolution of indiscriminate altruism in meerkats and the association between group relatedness and kin-discriminate altruism reported across vertebrates more generally.
Kin selection theory suggests that altruistic behaviors can increase the fitness of altruists when recipients are genetic relatives. Although selection can favor the ability of organisms to preferentially cooperate with close kin, indiscriminately helping all group mates may yield comparable fitness returns if relatedness within groups is very high. Here, we show that meerkats (Suricata suricatta) are largely indiscriminate altruists who do not alter the amount of help provided to pups or group mates in response to their relatedness to them. We present a model showing that indiscriminate altruism may yield greater fitness payoffs than kin discrimination where most group members are close relatives and errors occur in the estimation of relatedness. The presence of errors in the estimation of relatedness provides a feasible explanation for associations between kin discriminative helping and group relatedness in eusocial and cooperatively breeding animals.