squeenie said:
Could the way the brain develops also be genetic? Like with how a person grows physically is genetic? Sounds like an interesting topic for research...
Yes, it could, but in terms of large social differences, evidence indicates that's not the case.
For example, a recent study I quoted in another thread demonstrated that Americans tend to approach judgement from a literal perspective whilst Asians tend to approach it from a lateral perspective; when each race had to perform the other type of judgement, the same area of the brain in each case was working overtime to account for the type of judgement which the brain wasn't used to. That is: the brains developed differently (because brains are extremely plastic for about 20 years after birth, and then some) but in both cases, used the same part of the brain for
foreign judgements/decision making.
The more one identified with their respective culture, the stronger this "judgement gap" was found to be, regardless of actual racial background. (Id est: it's probably not genetic.)
As I said before, you can only really imply genetics when there has been a sufficiently large amount of time for evolution to work on (and you'd typically want a small starting population or an extremely aggressive mutation in terms of fitness). A few thousand years is nowhere near enough, and the last population bottleneck in humans was at about the same time as the development of language (70,000 years ago - Toba catastrophe). And it's doubtful it's an aggressively competitive mutation because such a thing would be rather easy to detect. I believe genetic variation in humans is startlingly low (probably in part because of the Toba bottleneck which reduced the human population on Earth to about 1,000 to 10,000 people).
Altering how one grows physically often results in many neutral variations. Altering how the brain grows however - most mutations there are deadly or result in significant fitness loss. As such, it's not hard to see why there appears to be less neural variation compared to physical variation.
None-the-less, a few well-known neural variations do exist such as:
ADHD, which increases evolutionary fitness (accounting for the large number of people with the mutation: about 5 to 6% of the Western world and 8 to 10% of the entire world) - it is intelligence neutral, with anecdotal evidence suggesting it increases intelligence slightly;
Autism, which may decrease fitness based on high incidence of asexuality and poor social integration - fairly intelligence neutral, sort of trading emotional intelligence for other areas of intelligence.