I think you mean 'race' is a social construct, because it is. It is something that is made up as a useful categorization tool, but it isn't really, "real."
We are all related. How do you tell the child of a black man and a white woman that "race" is a real thing?

You can't, because it isn't. There is only one race, the human race, homo sapiens.
I mean, I grow tired of the ignorant folks from the white nationalist/supremacist sites that come here and want to tell me, someone that studied physical anthropology, that there is any quantitative or qualitative differences between blacks and whites. . . there isn't.
Hell, we have some black forum members that are so attached to their race. . . which, having had shade thrown their way their entire lives, I can understand, but, they have gone out of their way to convince themselves that white people and black people are actually of a different type. . . they aren't. They have convinced themselves of the superiority of "blacks." But? If we are all one? That is nonsense. People are people, and they all have the same strengths and weaknesses.
If you do genetic studies, you will find, there is more genetic variation within white populations and within black populations than there is between them.
. . . with that said, racism? That is what is known as IN-GROUP behavior and OUT-GROUP behavior, preferences that develop subcultures due to melanin differences? yeah, that is a real thing. But, these In-Group behaviors also develop among and between the old and the young, between and among different religious groups, between men and women, different sexual preferences and habits, different political beliefs, etc. etc.
It is basically something that will always be here, and will never go away, it is something all animals are born with, and humans will not be exempt. You can't get rid of racism any more than you can get rid of being suspicious of strangers or folks that are different than you are.
The only way to reduce it is through education.
Humans always find ways to separate themselves out into like interest groups.
This is one of the co-authors of that paper.