Here is a section from the New FamilySearch manual:
Racists are unfortunate, ignorant souls. They fail to realize that every white American has African blood flowing through his veins.
After all, the MRCA study shows that, setting aside a few isolated Siberian and Pacific Islander populations, each of us is descended from 80% of the members of every ethnic group existing in 1 A.D. (and collaterally related to the other 20% of each ethnic group).
Thus, every white American has millions of black African ancestors. And every black American has millions of white ancestors.
Probably about 15% of the ancestors of each white American were black Africans.
Each of us has blood from Nigeria, India, China, Iran, Mozambique, Russia, Tonga, the Native Americans, the Australian aborigines, Sweden, Egypt, etc.
Historical records and archaeological remains demonstrate there were migrations going on continually all throughout history. Jews migrated to Japan 2,000 years ago. Africans traveled to the Americas many centuries before Columbus. Ghengis Khan caused a massive influx of Asian blood into eastern Europe.
So, there is no such thing as a racially-pure people.
We are all mongrels.
We are Heinz 57.
Instead of disparaging other racial and ethnic groups, we should recognize and embrace our common heritage.