it is very likely that highly intelligent people are living in the refugee camps in Zimbabwe, the slums of Bombay and the rice fields of Bangladesh, but who are not able to live self-actualized lives due to the very limited opportunities they have because they were born where they were born.
One of my extended family members grew up in a small village in Bangladesh. He'd stay up studying until 4am in the morning. He later worked in Japan as an engineer. he's now a professor at NUS in Singapore. I think the world is flat enough for the gifted to succeed. I have no doubt there are bright people from the areas you've mentioned.
But nurture of today is a different argument to millions of years of evolution. A normal curve is exactly that: normal. There will be a mean average, meaning a standard distribution applies.
As to education: of course one will do better in life born into a better educational systems. But why is is that some cultures have better education system? Could it be that (I think here, not fact), low EQ nations full of corruption don't care for others as much as high EQ nations, hence the schools are a bad state? I think so, unfortunately.
osmanthus: Since evolutions happens over millions and millions of years, I think it is important to ensure that causes are taken into account with certain groups evolving in one area over a very long period. Migration is a lot quicker than evolution. Just look at the technologically advance Australians, they never evolved in a hot climate otherwise they'd be just like the Indigenous Australians. And again coming back to nurture, give the Indigenous Aussies a good education and they will do well.