Pregnancy improves women's brains for motherhood
(media.scored.co)
The reason lions and tigers are different species is because the offspring are sterile. If mixed-race black/white children were sterile, blacks and whites would be same genus/different species. That isnt the case, they can breed true (in fact, most america "blacks" probably have more white or jew in them than negro), so they are the same species. However, I thin its more of a breed thing, like dogs.