I can’t help but to read this as “guess the omitted variable”. There’s just no way of controlling for everything that might explain this, and it’s obviously not the grandparents’ time in educational institutions in itself that does the trick.
Thankfully, one of the authors summarized it well:
This opens up a myriad of possible explanations and will need to be replicated.
It’s easy to imagine ways this effect makes perfect sense, especially if it’s small. So the question kind of becomes what they have managed to successfully control for.
As far as I’ve understood, a lot of nature religions do go a long way in recognising our common origins. Not as evolution as such, but more because we’re all parts of a common body somehow. In that sense they might have been closer to getting it right than messianic religions. Not that it takes all that much.
Learning about the belief systems of indigenous people in Latin America is incredibly interesting. There’s a lot of underexplored ancient philosophy in there, and it is still being kept alive through oral traditions often in increasingly small communities.