Here’s a twin study on heritability of “the Dark Triad of personality — Machiavellianism, narcissism, and subclinical psychopathy — and moral development.” The study reports high heritability of evil traits and low heritability of virtuousness.
My takeaway from this (to the extent you can say anything) is that virtue is the absence of evil and that people are inherently good (or evil-free) unless they have genes that take a wrong turn.
(I hate posting this kind of overly simplistic view because all the real scientists dismiss this out of hand. But I think it does show at least a trend or perhaps way of thinking about evil).
Campbell J, Schermer JA, Villani VC, Nguyen B, Vickers L, Vernon PA.,”A behavioral genetic study of the dark triad of personality and moral development,” Twin Res Hum Genet. 12 :132-6 (April 2009)doi: 10.1375/twin.12.2.132
The present study is the first behavioral genetic investigation of relationships between the Dark Triad of personality — Machiavellianism, narcissism, and subclinical psychopathy — and moral development. Participants were 154 monozygotic twin pairs and 82 same-sex dizygotic twin pairs. Higher scores on Machiavellianism and psychopathy were positively correlated with low levels of moral development; high psychopathy scores also correlated negatively with high levels of moral development. Individual differences in lower levels of moral development were attributable to genetic and nonshared environmental factors but, very interestingly, individual differences in the highest levels of moral development showed no genetic basis but were entirely attributable to shared and nonshared environmental factors. Finally, correlations between the Dark Triad and moral development variables showed no genetic basis while correlations among the moral development variables were variously attributable to correlated genetic and correlated environmental factors.