A few years ago there was a huge stir caused by the publication in Nature of a somewhat mathematically abstruse paper, The Evolution of Eusociality. It was huge enough that it got a treatment in The New Yorker, Kin in Kind. Many of the reactions were basically tribal. Most geneticists were rather upset with the publication of this paper for a variety of reasons, both substantive and stylistic. In contrast, I’ve engaged in conversations with ecologists who assume that the authors of this paper basically proved that old-fashioned inclusive fitness theory, as first outlined by W. D. Hamilton in the 1960s, had been shown to be superfluous and irrelevant.
A major point by one of the authors of the original paper, Corina Tarnita, is that their detractors didn’t really engage with the model that they laboriously outlined. Well, until now. A new paper in PLOS BIOLOGY takes the model from the 2010 paper, and argues that it isn’t really all that robust, and therefore does not really speak to whether inclusive fitness is useful at all in comparison. The paper is Relatedness, Conflict, and the Evolution of Eusociality. Nicely it provides a lot of code to go along with the assertions, so I invite readers to dig into it, and the original Nature paper from 2010. And while you’re at it, W. D. Hamilton’s first volume of collected papers which addresses his work on social evolution, Narrow Roads of Gene Land, is highly recommended (if you want some full-throated anti-Hamiltonian viewpoints, Unto Others: The Evolution and Psychology of Unselfish Behavior, might interest you, though only the first half is much focused on evolutionary genetic aspects).
If I had to bet I would say that inclusive fitness is very important across many branches of the tree of life. But, I’d also suggest that among organisms with particular complex and elaborated social structures (e.g., humans) there is probably a lot more going on. Also there is more than can be explained by reciprocal altruism. So I’ll go on the record that for humans something similar to multi-level selection theory does have something useful to add, especially when it comes to cultural evolution, where standard objections to low between group variance do not hold. It’s just that this is evolutionary, not revolutionary, science. I wish the enemies of inclusive fitness would calm down with the bromides, and just get on with good science. The truth will tell.