Eusociality, particularly focusing on the presence of certain altruistic sterile

Question

Eusociality, particularly focusing on the presence of certain altruistic sterile organisms within the social set-up creates questions as to why would the process of natural selection have favoured the persistence of such genes especially in hymenopteric species. One explanation (provided probably by Hamilton) pertains to very similar genetic constitutions of females of such species (owing to haploid nature of males), which increases genetic similarity between the female members of the social group. Thus it would be more "beneficial" (i.e., favourable for the persistence of similar genetic builds) for a female worker to help the fellow siblings, to which it bears greater genetic similarity, than its own offspring to which it bears a lesser genetic similarity. This might in a deeper way explain altruism in case of hymenopterans where the male is a parthenogenetic haploid and the female is diploid.

But why would the sterile condition of the workers in case of almost all eusocial groups be favoured by natural selection on grounds that it improves the 'fitness' of the 'genetic build' of the workers and ultimately the sterile altruists benefit the persistence of its genetic traits? Moreover the altruistic nature of the haploid males also goes unexplained.

Explanation / Answer

I hope I've interpreted your question properly... It's an interesting question, but I think it's important to remember that evolution doesn't act on the two sexes separately. Sterile males might evolve and be maintained simply because they're good for their sisters or mothers. Sometimes genes that are advantageous for one sex are linked with genes that are disadvantageous for the other sex, leading to maladaptative traits in one sex. And of course, individuals don't necessarily forego opportunities willingly. If subordinates that attempt to mate are killed by the dominant individuals, then that trait is not advantageous. They'd be better advised to be altruistic and help their relatives, rather than be selfish and be killed (thereby depriving their colony of a worker). This would lead to selection for sterility.

It's also worth noting that while haploidy makes it easier for kin selection to evolve by increasing relatedness, it's not crucial. It all depends on the relative costs and benefits.

In these eusocial situations, nothing really makes sense until you summed the fitness of the whole lineage, not just one caste or one sex or one individual.

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