Why are you so interested in intelligence, specifically? I think the genetic differences are represented in a large variety of traits, intelligence probably being one of them.
For example - do you think that black people are not inherently superior at playing basketball?
The discipline of sports science is actually very decidedly settled on this point. Other than a shift in the bell curve for average height of approximately 5 inches (but otherwise still follows a normal distribution), there is and has been found zero correlation between any genetic attribute and success or likelihood of becoming a basketball player. Or indeed any other sport*. The only factors that have been found to predict likelihood of becoming a professional at any game or skill (incl. e.g. musicianship, chess, etc.) is time spent practicing that sport, and efficiency of the practice methodology.
Quite simply: there's a predominance of African-Americans in the NBA because a) basketball is an extremely popular sport among African-American communities, and b) basketball is a sport that can be practiced very cheaply, so there is a very large population of African-Americans who devote significant time to practicing the sport and so become very good at it. In the same way, there is nothing inherently genetic that would have predisposed a Hun or a Mongol to being a particularly exceptional horserider. It's simply that they spent
literally their entire lives riding, from before they could walk, to the day they died. You spend that much time doing a thing, and you're going to get very good at doing that thing.
You can see this same correlation of time spent practicing to populations who are good at Thing in baseball, where domination in the sport went through ethnic waves depending on among whom the sport was popular at the time. This is particularly poignant with baseball as, a) baseball for much of its history was not a sport from which one could make very much money, and so pursuit of a career in the sport was not held as a particularly prestigious or desirable endeavor among affluent communities, and b) Baseball was esteemed as an epitome of Americanness, and so it was seen as a popular means by immigrant communities of establishing and legitimizing their newfound American identity. In the 1840s, 50s, and 60s when the game was a gentlemanly club sport, the best players were white Englishmen/Americans. In the 1890s the sport was dominated almost exclusively by urban Irishmen. In the 1900s and 1910s the sport's locus shifted to more rural locations, and so was dominated by German miners and Southern farmers. In the 1920s, 30s, and 40s it shifted back to urban minority white groups (Irish: Ruth, German: Gehrig, Italian: Dimaggio, Jewish: Greenberg, Polish: Musial). In the late 40s and early 50s the color barrier was lifted, and African-Americans, among whom the sport had been exceedingly popular for the entirety of the sport's history, dominated the sport, and would do so for the next 30 years (Robinson, Mays, McCovey, Banks, Aaron, Gibson, Jackson, Henderson, Smith, Bonds, Griffey Jr., etc.) In the 80s and 90s MLB teams started building facilities in Puerto Rico and the Dominican Republic to train and develop players, and so we see a concordant domination of the sport by Puerto Rican and Dominican players throughout the late 80s, 90s, and early 00s, particularly as the socio-political locus of the sport in the States shifted away from poor inner city black and minority communities to suburban middle class white communities. Currently the sport is dominated by: Venezuelans, Dominicans, Cubans, and Middle/Upper Class Suburban White People.
*There is really only one sport where there is any correlation whatsoever that has been found between a genetic trait in a geographically correlated population and a specific sport, and that sport is distance running. And that correlation is a single, relatively small valley in Kenya, where people there have evolved a type of slow-twitch muscle in their legs that is able to sustain activity longer and on less oxygen than an average human leg muscle. This follows because, unlike literally any other sport, distance running is a sport that tests an actual evolutionary factor in our historic natural selection. Populations in that region have historically hunted prey by running it down over long distances, and they have been hunting in that same way for nearly the entire history of humankind. So it stands to reason that over long periods, the population would select for individuals who have muscles that are better adapted to distance running. Even so, this genetic correlation singularly applies to that small population in Kenya. When you control for that population, you again find that the sole statistically significant factor in skill at distance running is time spent practicing distance running. And even looking just at that population, it isn't solely because they have muscles that predispose them to be better runners, but, because that population has been doing distance running for tens of thousands of years, they have honed and refined practice methodologies over the milennia, and so are the best runners, not just because they have the best muscles for the job, but also because they spend an inordinate and extremely efficiently applied amount of time just running.