Another point not to be overlooked is the effect on groups like the Amish, and certain sects of Judaism, for that matter, of their formation and strict endogamy. The Amish have very high rates of recessive disease. The worst I've personally ever seen.
See:
http://www.biochemgenetics.ca/plainpeople/view.ph
Other genetic correlations are more difficult to quantify. Almost 90% of teens choose to be baptized and remain within the church. I've wondered how much of that stems from the fact that the original group attracted to this religion must have been rather conformist and authoritarian genetically, an inclination reinforced by constant intermarriage, versus the natural reluctance to cut off all ties with family and friends and community when one lives such an isolated and circumscribed life, as any deviation from the norms by an adult results in "shunning" or outright excommunication and banishment. (They also rather intelligently permit a certain amount of deviation in teens through a period they call the "
rumspringa.)
https://en.wikipedia.org/wiki/Amish
The same applies to their pacifism. They hold to it despite any provocation, as they do to a generous and forgiving stance in response to any violence inflicted on them. There is widespread admiration, which I share, for their behavior in these instances, as when they responded with forgiveness and prayer to a mass shooting by some deranged man who attacked the children in one of their schools. Again, I wonder how much this sort of response is due to genetic predisposition versus indoctrination. I would think that one reinforces the other.
https://en.wikipedia.org/wiki/West_Nickel_Mines_School_shooting#Amish_community_response
I do think one thing said on another thread about the fact that strict adherence to a traditional religion which promotes having large families means that the families will be poor and a burden to the state is disproved by the Amish, and by the Orthodox sects of Judaism for that matter. The Amish are remarkably prosperous. All of that free labor from their children, and an admirable work ethic, plus the pooling of community resources means that their farms, even without the use of modern machines, are very profitable. They are so profitable that they are able to accumulate enough money that they can buy farms for all these young men even though it means scattering communities far and wide in order to have access to cheaper land.
For what it's worth, I have a bit of experience with them, and not just through tourism in their area, although I did that too. I was and am rather fascinated by the simplicity of their way of life, and I admire, as I said, their adherence to the best of the Christian message, to the extent that I spent a week with my children in a type of agriturismo run by Mennonites (a less strict group) where you live their life, performing the chores etc. I thought it would be a salutary experience for my children. It wasn't one of my better ideas, in their opinion.
I personally had no difficulty at all with the physical aspects, and quite enjoyed that part of it. What was absolutely unattractive was the total conformism, and most of all, the complete and utter lack of an intellectual life. That also might have a genetic source, in my opinion. This wasn't a sect formed by schismatic intellectuals.
Nor is everything sweetness and light in their family lives, despite all this professed emphasis on mercy and love. A great-uncle of mine was a refugee in Switzerland during the war and worked on one of their farms. He said the authoritarian attitude of the father as the head of the household, and what he felt was the sometimes outright brutality toward his wife and children was terrible. They certainly don't spare the rod. He forged a bond with the eldest son who bore the brunt of the physical punishment, to the point that this boy decades later, then a man, came to visit my relative when he in turn emigrated to the New World to join one of the American Amish communities. Granted that this family may not have been representative, it's informative that even this wasn't enough to make him leave the sect.