I'm sure it has genetic components, but the question for me is rather whether those components differ between peoples. I'd assume that evolutionary pressure selected quite heavily for people who can be trusted to cooperate.

But there are also obvious evolutionary pressures towards self-interest, even when it means breaking promises/trustworthiness. (Remember, selection happens at the level of individuals, not of whole groups and societies!) The balance between the two pressures could be different in different environments. In other words, it's quite possible that one environment could select more for trustworthiness, another more for untrustworthy self-interest.

Not being a dick and working together without everyone constantly on edge that everyone else is going to screw them the first chance they get is a totally valid strategy, even from a self-interest standpoint.

Mutual Aid: A Factor of Evolution

http://www.gutenberg.org/ebooks/4341

Crikey, anyone seriously think its a genetic trait?

Do you imagine the children taken into care at a young age turn into bad people just like their parents anyway?

Surely everyone thinks that trustworthiness is about poverty, inequality and values?

Actually, what I recall from reading studies of adoption and criminality (it was a few years ago, though, so I don't remember the authors or exact titles to find them) the "the children taken into care at a young age turn into bad people just like their parents anyway" has a truth in it - if you analyze the heritability of antisocial behavior and criminality (and the heritability clearly exists) to see how much of it is e.g. "nature vs nurture" or genetics vs environment and socioeconomic status, then about half of it still remains in case of adoption to a 'low risk' environment.

One plausible explanation for some of that, which wasn't analyzed there, but has some basis in other research is that things like risk-taking behavior or being prone to addiction are quite genetic.

But in any case, for many(most? all?) "moral" characteristics saying that they're only about "poverty, inequality and values" is wishful thinking. Yes, they are in part about that, but they are also in part about genetics; the answer to "nature or nurture" pretty much always is both.

Quite so. Most twin studies on the subject turn up similar findings: https://evolutionistx.wordpress.com/2015/10/02/time-preferen...

"The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity."

So impulsivity (which is obviously closely related to your propensity to betray the trust of your fellow-man for a short-term gain) appears to be a combination of genetics and random luck (non-shared environment).

I don't know about trustworthiness in particular, but lots and lots of personality traits turn out to have a heritability of about 50% (or more), so much so that it's a decent rule of thumb to guess that a trait is about 50% heritable.

Everyone thinks that way, but it turns out the science says otherwise.

I am more inclined to believe it is a CULTURAL trait.

You and the folks who down-voted the parent comment agree on that point. That doesn't make it true.