Most of the best engineers are (in most but not all cases) white or Asian. It's not because they're any smarter than minorities, it's because Europeans and Asians have been blessed by history and geography. In almost every aspect, Europeans have had it a lot better than Africans and other ethnicities and cultures. For example, Europe is much easier to farm than most of Africa because of climate differences. So while Europeans could harvest the crop and spend all winter in their houses tinkering around, Africans historically had to hunt and gather year round and didn't have as much free time. Africa's climate also lends itself to having much more serious diseases.
There are social, political, environmental, and geological factors that all add together to determine how "well off" a society of people will be, how quickly they historically would have been able to advance and conquer their neighbors, grow rich off trade, educate their children, etc.
If slavery had been outlawed in the United States since the 1500's, and Africans moved to the New World as freemen without prejudice, you would see just as many African Americans (proportionately) graduating university and becoming great engineers as white or Asian Americans.
A lot of people don't understand why poor African Americans and other minorities don't just "pull themselves up by their boot straps" out of poverty, and the simple truth is that it's just not that easy for most people. In fact, in most cases it is impossible to pull yourself out of poverty without some serious luck. It has been proven that in homes where the parents yell at each other, young children have much higher levels of cortisone (a stress hormone) in their blood stream. This leads to extensive cognitive impairments that will last for the rest of their lives because cortisone literally STOPS brain development in its tracks. Thus, even in a brain scan, poverty is easy to see even at five years of age.
This is just one example of how poverty and historical injustice can lead to centuries of inequality, even when slavery is outlawed. It takes MANY generations for the harm done by slavery to disappear entirely. I predict that even 200 years from now, the insidious effects of slavery will still be apparent on African Americans in US society.