I don’t mean from a nutritional standpoint, but a behavioural perspective. Smaller groups would have an higher percentage of responsibility per individual to be vigilant and proactive.

It would make sense to me that evolutionary there would be different mental development paths depending on the requirements of their situation.

This is coming from my understanding that ADHD is more prevalent in stressful upbringings.

If adhd is heritable, then the stressful upbringing could be symptomatic of the parent's condition instead of causal.