Some ants give up reproduction and take care of the queen ant’s young. This altruism (“eusociality”) seems to contradict selfish natural selection. Why would these ants be so selfless?
A solution seems to arise via the theory of kin selection: an ant maximizes the sum of its own payoff and the payoff of a co-player weighted by how closely related they are. A rather precise formula was provided for this by the biologist W.D. Hamilton and it provides the underpinning of sociobiology. It might also provide an explanation for eusociality: the baby ant you are looking after is closely related to you. Also, via a quirk of fertilization, related ants share 3/4 of their genes increasing the “inclusive fitness” payoff behind the theory of kin selection..
But now along come some contrarians, Martin Nowak, Corina Tarnita and perhaps most surprisingly, the sociobiologist E.O. Wilson. In a recent paper in Nature, they argue
Eusociality, in which some individuals reduce their own lifetime reproductive potential to raise the offspring of others,
underlies the most advanced forms of social organization and the ecologically dominant role of social insects and humans.
For the past four decades kin selection theory, based on the concept of inclusive fitness, has been the major theoretical
attempt to explain the evolution of eusociality. Here we show the limitations of this approach. We argue that standard
natural selection theory in the context of precise models of population structure represents a simpler and superior approach,
allows the evaluation of multiple competing hypotheses, and provides an exact framework for interpreting empirical
This has set off a firestorm – witness the huge number of letters arguing their paper is flawed. The letters are gated so I have not read them but an economist can certainly read the ungated original paper and get some sense of the controversy.
First, Nowak et al. argue that the simple equation that Hamilton wrote down to capture inclusive fitness is too special. It does not account for complementarities in payoffs and assumes pairwise interaction. It often gives results which would come from maximizing fitness alone. The Hamilton inequality is that cooperation occurs if R>c/b where R is relatedness, c is the cost to the cooperative action action and b is the benefit. It already looks quite special as it seems to assume interaction payoffs are given by the Prisoner’s Dilemma. This part of the Nowak et al critique does not look controversial to an outsider.
The second part is weird, at least to an economist. Nowak et al offer their own theory of eusociality. They compare two scenarios. In one, the queen ant lives a solitary life in her nest as all her kids wander off and start their own nests (assume asexual reproduction for simplicity). So the queen has to defend her own nest against predators and this affects the birth and death of her kids. In the other scenario, the kids stay and look after the newborns, eusociality. This can increase the birth rate as the queen is less distracted by defense activities, and cut the death rate as the nest is well defended. But why would the ants stay and defend and not wander off? This seems to be the controversial part: Nowak at al assume the ants are robots pre-programmed to stay and hence they do not face a choice. They do not get a good wage or have a terrible outside option, as we would say in economics. Rather, they are like the Borg in Star Trek New Generation. This smacks of group selection not individual selection. And E. O. Wilson is a co-author on this theory. No wonder it is controversial.