The demonstration that genetic polymorphisms for the OXTR are associated with human prosocial decision making converges with a large body of animal research showing that oxytocin is an important social hormone across vertebrates including Homo sapiens. Individual differences in prosocial behavior have been shown by twin studies to have a substantial genetic basis and the current investigation demonstrates that common variants in the oxytocin receptor gene, an important element of mammalian social circuitry, underlie such individual differences.
And the SNPs from the HGDP (G = C & A = T for the first SNP, or at least the paper and PubMed agree on this):
Related: It’s hard out here for a vole. Heritability of the Ultimatum Game. Altruism and Risk-Taking: Kinda Heritable. Can someone put the psychic unity of makind out of its misery? DRD4, politics & friendship.