I have a theory that trauma (on a broad scale) is linked to higher intelligence. Ashkenazi Jews have been historically persecuted and research finds descendents more prone to PTSD/Anxiety and mental health problems (Science now knows that trauma can be passed down epigenetically). However, they're also consistently the highest IQ ethnic group. We also know that traits like Narcissism often arise as trauma responses - a strong ego develops to protect against inner wounding, and is driven to external achievement as a means of soothing the 'hole-in-the-soul'.

I don't mean to spark a discussion about Eugenics here, and I certainly don't think that group level differences should drive policies or that one group is better than another intrinsically. However group level or cultural differences are evident to me, it's absolutely real. It's just interesting to theorize the mechanics of the development of intelligence.