On the back of robust experiments like these, I have changed my mind about relatedness being the primary dictator of social evolution. Insects are unable to discriminate relatedness on an individual level. Instead, relatedness may act at the colony/population level, or simply in distinguishing kin from non-kin. This make sense. An individual-level kin discrimination mechanism is vulnerable to invasion by an occasional nepotist, who would favor its closest relatives over others. As the gene for nepotism spreads, the variation on which the kin-discrimination is based (e.g. chemical or visual cues) will disappear and individuals will no longer be able to tell kin from non-kin, let alone full siblings from half siblings: sociality breaks down.
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