The evolution of spite entails actors imposing costs on ‘negative’ relatives: those who are less likely than chance to share the actor’s alleles and therefore more likely to bear rival alleles. Yet, despite a considerable body of research confirming that organisms can recognise positive relatives, little research has attempted to show that organisms can recognise negative relatives. Here, we extend previous work on human phenotype matching by introducing a cue to negative relatedness: antiself-resembling faces, which appear dissimilar to an individual’s own face. Participants made trustworthiness and attractiveness judgements of pairs of opposite-sex, antiself-resembling faces and similarly manipulated control faces, as well as judgements of pairs of opposite-sex, self-resembling and control faces. Analyses revealed positive preferences for self-resembling faces but negative preferences for antiself-resembling faces. Moreover, participants significantly preferred control to antiself-resembling faces in trusting but not in attractiveness contexts, an effect that mirrors previous findings of context-specific effects of self-resemblance. This is the first clear evidence that humans are sensitive to negative relatedness cues, and suggests potential for the adaptive allocation of spiteful behaviour.
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