I have used this analogy before. If you take a German kid and a Conglese and swap their place of upbringing, the Congolese kid will become advanced while the German will stay stagnant having been raised in the environment provided to him which is in the Congo.
if we're talking about one generation, with today's realities, then the german kid would kick major a$$; he'd grow up in an environment where there are more potentials for him to utilize his inherited natural skills and advantages; whereas the congolese kid would be grown up in a society less in need of what he's to offer and therefore would be rendered useless. history is your prove on this.
There is no "intelligence" differences between humans along race. All humans are equally capable of the others' intelligence but it is a matter of who rears and gives an opportunity for that intelligence.
you're right about the first part. because by default races have the same potential when it comes to intelligence. but, in today's world, its a fact of reality that categorically some races are more advanced intelligently than others, e.g. the german 'race' and the congolese. why? because something like intelligence takes over many generations to develop, its just doesn't happen over night. so, for example, if a german kid and congolese were raised in the same environment and given the same opportunity, then, in theory, the german kid would still come ahead in life. because the german kid has genetic advantages (advancing intelligently was necessary for the survival of his ancestors), whereas the congolese kid has the handicap and disadvantages of having ancestors whom learning and attaining knowledge wasn't part of their way of life (it wasn't necessary for their survival). but this isn't linear and, more importantly, its not irreversible. one of the biggest threats to the survival of a race - and also most helpful in the development of intelligence - is when it comes in contact with a more advanced race; unfortunately for the races of sub-saharan africa this process has only start recently, in an age where the intelligence gap between the races has been larger than any other time in history.