If you replace white and black child, and white child send to Africa, and black to America, who will be smarter than?
What do you think?
If you give them equal opportunity, you will find out that blacks are intelligent and smart as any white man.
I have already posted evidence to counter your claim. Check this:
https://bitcointalk.org/index.php?topic=1696031.msg17037672#msg17037672Black children adopted by white foster-parents have lower IQ, when compared to white children adopted by white foster-parents. Now do you admit that it is hereditary?