As noted above, genetic similarity between gang members with similar phenotypes may indeed be higher than that among the non-associated individuals from the general population. The plausibility of extension of the notion of kin to non-relatives is illustrated by the well-publicized effective sexual taboo not only among close relatives (incest taboo), but, independent of sibship, among children raised together, as in kibbutzim (Shepner, 1971; Wilson, 2000). The genetic correlations due to homophily may thus be the ultimate evolutionarily significant goal of such group associations, because it increases the probability of survival and reproduction of identical genes—without the negative consequences of inbreeding where genetic correlations are primary, rather than secondary as under assortative mating or homophily. The genotype-driven search for permissive environment, active genotype–environment correlations, could be a means to achieving this goal. Therefore, regardless of whether there are blood relatives in the group, altruistic behavior toward the gang members may be consistent with the induced genetic correlations between non-relatives and the extension of inclusive fitness to them. It is noteworthy that this group behavior has been shown to depend on
