Because of the LONG and STORIED history of people claiming that people of African descent are somehow less evolved or closer to a gorilla or chimp than other human population groups.
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I never heard that. Is it true?
It is true that racist idiots have attempted to claim such.
It is most certainly NOT true in any sense of the word in reality.
All humans are related by RECENT common descent. No human population is any closer to or further from any non human primate.