What Hamilton was trying to deal with was essentially altruism or
"The concept of inclusive fitness argued that an organism could increase its genetic success not merely by reproducing itself, but also by aiding the reproduction and survival of relatives carrying some proportion of identical genes."
When you think of it altruism is actually contradicted by natural selection. Yet rather than being an aporia, it falls into a category that is becoming increasingly common amongst high level thinkers in both science and philosophy. For instance Thomas Nagel, who defines himself as an atheist, still maintains, in his current book, Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly False, that pure naturalism cannot effectively explain the emergence of consciousness. The "inclusiveness"of a thinker like Nagel bears comparison to Hamilton who also exhibits a kind of scientific thinking that takes nothing for granted. But Hamilton who believed in Segerstrale's words that warfare "could be seen...as adaptive rather than pathological" could also be quite provocative. Thinkers like Hamilton and Nagel, along with the utilitarian philosopher Peter Singer of Animal Liberation fame are part of the "more things in heaven and earth" club who ask uncomfortable and bothersome questions that are bound to upset the applecart for purists who are unable to tolerate a multivalent view of the world. Philosophic and scientific multitasking is the name of this game.
"why an animal should forego reproducing...or expose itself to danger to warn its fellows of a predator."