Intelligence is a combination of physical traits and the social environment that develops and nurtures those traits. Most humans possess the physical traits to be intelligent. In that sense, the genetic aspect plays very little role.
It is not easy to measure intelligence. We have a flawed tool, IQ, that attempts to do it but is itself biased. But even with that, 68% of all the respondents fall within +/- standard deviation of 100.
You will wonder why I call it a flawed tool. For example, there are a few questions in it that measure ability to analyze volume, temperature, weight, etc. In the US it is not in metric while it is in metric in the rest of the world. So, if you bring a foreigner to the US and measure their intelligence, they will artificially get a lower score because of the measurement units.
So, the biases resulting from the social environment will affect the measurement of their intelligence. The same thing happens with the different cultural segments in the US. The IQ is designed by mainstream white scientists and it will fail to accurately measure non-white intelligence. This might be by design or by ignorance, I cannot speculate.