When an all/mostly black country invents something like the Internet, and then creates a website like Wikipedia, and then most of the nerds it attracts to administrate it happen to be black male nerds, then, yes, you'll see a different demographic mix. But until that happens, you'll see demographic trends that are likely (and reasonably) going to be heavily influenced by their starting conditions.
they're working on improving the gender balance, but i suspect that the format will still retain this skew simply due to societal/demographic reasons.
I don't know that that means that there was any overt or covert racism, but there is definitely a contributor bias :P
† upon further investigation i have not been able to find references to racial demographics for wikipedia. Consider this hearsay.