You seem to be dancing around the obvious and missing it. Genetic differences influence behaviour.
Sure. So do socioeconomic differences. So does cultural indoctrination. These are three corners of a triangle of motivation, and you can’t be sure how much each of these is influencing the numbers without careful study. Could be one, could be all three, could be different ratios of each. To be sure we’d need a very detailed multivariate analysis.
The thing I find interesting about the mapping exercise in the article is we can see clear geographical boundaries between regions that are socioeconomically similar, which lends me to think that the socioeconomics might not be the most important factor. It’s hard to say, but I don’t recall too many people looking into this.