I have a theory! I have mentioned the topic before but from a different angle.
Children of those who came from the North of the Wood Lands to migrate to the Southern Island have a higher level of intelligence and brilliance (note: not hard work — that one comes from Further Further North). Their parents have a degree of refusal to accept their systemic fate, have a drive that seek change, a sharp awareness of plausible alternatives and a keen opportunism. That is, assuming all other things (like environment and conditions) being equal — though that is the main difficulty. Leaving room for exceptions.
It’s like how being born in the lusty stealth of nature take more composition and fierce quality.
Yet, I think I might be making a baseless assertion. First, the numbers are smaller to begin with and hence statistical comparison with the Southern Locals cannot be drawn and my theory cannot be proven. Second, intelligence and brilliance cannot be quantified either. Especially when i have been vague about what “brilliance” entails.