Functionally equivalent OPRM1 variants have evolved independently in two primate lineages, the rhesus macaque 13 and man 11. In both species, minor allele carriers are more sensitive to disruption of social attachment bonds 58,59. In rhesus, this is accompanied by bold - exploratory traits, while lower conscientiousness has been observed in human 118G carriers 13,58,60. These traits may have been advantageous in the evolutionary history of the respective species, and recent studies suggest that the 118G allele has been under positive selection 61. In contrast, the ability of these variants to modulate DA responses to alcohol is likely a coincidental evolutionary byproduct.
