Again, emphasis on small. The causal effects identified in the papers were in the range of about 0.1 standard deviations of the outcome per standard deviation of the exposure. That is, if you worked hard to move culture in a particular direction, I would expect at most 10% of the change you bring in to persist in future generations.
It is plausible that smaller effects exist—which we would not have enough statistical power to detect. It is unlikely that stronger effects exist, since those would be easier to detect. And I would correspondingly have expected to be flooded by papers studying how your ancestors’ religion explains your Netflix watching habits.
Perhaps the similarity between areas is caused less by the effects being small, and more by cultural dispersal and diffusion? I know that my ancestors, the early Christians on the Mediterranean, had a huge effect on my culture today. But since they had a similarly huge effect on the descendants of Brits and Swedes, that might not be very visible if you compare their geographic place of origin with other parts of Europe. In fact, I’m myself also descended from the British Isles; the descendants of the Classical inhabitants of Iberia are also the descendants of Classical “barbarians”. I’ve read that it only takes ~1,500 years for someone to become the common ancestor of all Eurasians. (Link goes to where I read it, not the original source which I haven’t followed up on.) Weak observed effects of medieval culture on Italian cities may be less that cultural effects decay, and more that modern Italians have ancestors from every city on the peninsula.
I think this is a good point and worth emphasizing.
The studies are focused on studying variation across populations—if everyone in the studied population is equally affected by the cultural forces in question, then this will not show up in the results.
This still means that in practice deliberate cultural interventions are less appealing. In this interpretation, you cannot work towards improving the values of a subpopulation and hope that they will persist through the time—the forces of dispersal and diffussion, as you say, will slowly wilt away the differences.
In order to effect deliberate change, you will need either a very convincing reason to believe that the change you are introducing will survive cultural diffussion, or a mechanism for affecting a very large population.
Epistemic status: just spitballing. But:
Perhaps the similarity between areas is caused less by the effects being small, and more by cultural dispersal and diffusion? I know that my ancestors, the early Christians on the Mediterranean, had a huge effect on my culture today. But since they had a similarly huge effect on the descendants of Brits and Swedes, that might not be very visible if you compare their geographic place of origin with other parts of Europe. In fact, I’m myself also descended from the British Isles; the descendants of the Classical inhabitants of Iberia are also the descendants of Classical “barbarians”. I’ve read that it only takes ~1,500 years for someone to become the common ancestor of all Eurasians. (Link goes to where I read it, not the original source which I haven’t followed up on.) Weak observed effects of medieval culture on Italian cities may be less that cultural effects decay, and more that modern Italians have ancestors from every city on the peninsula.
I think this is a good point and worth emphasizing.
The studies are focused on studying variation across populations—if everyone in the studied population is equally affected by the cultural forces in question, then this will not show up in the results.
This still means that in practice deliberate cultural interventions are less appealing. In this interpretation, you cannot work towards improving the values of a subpopulation and hope that they will persist through the time—the forces of dispersal and diffussion, as you say, will slowly wilt away the differences.
In order to effect deliberate change, you will need either a very convincing reason to believe that the change you are introducing will survive cultural diffussion, or a mechanism for affecting a very large population.