...How blacks were treated in the past does not affect their behavior and performance now. How blacks behave and perform now does affect the way they are treated now.
If you're speaking of a history and pattern of abuse and legislatively sanctioned disadvantages that impede forward momentum, then of course how Black people have been treated in the past has a cumulative impact on our race as a whole. But this is true of any group when
all else is equal. There is no comparable group to people of African descent in the United States.
Think of it this way. Back before the advent of the internet the only way to get information was to go to the library. Even if your family was big into reading materials as mine was, our World Book encyclopedias were only as current as the date of publication which is why a "year book" was issued to members annually with current events of the previous year. So with that background in mind, let me give you a scenario
Let's say you want to be an air traffic controller because a friend of the family is an air traffic controller and you think it's a interesting field. So you ask someone (no internet) and discover that the first step is you have to pass the civil service exam that is administered for anyone wanting to work in that field.
Do you think you would do well or better on passing this exam if you know what to expect when you take it? How about if you had the ability to practice taking those types of written government issued exams? How many people do you think even know that preparatory materials even exist? Remember this is way back before there was an Amazon "book store" or anyway to do any online research, if you even knew to try to locate resources to help you not just pass the exam but to end up in the top 10%.
People in the know, would be directed to their local library which should have copies of the test training materials - The Civil Service Test Exam books. But if you were in a legally racially segregated community with less, little or no money to pay for a "separate but equal" library and by law, you're not allowed into the "white library" do you think that would put you at a disadvantage?
None of this is a matter of pure intelligence, its familiarity, opportunity, attitude, beliefs and support systems.