See my post above, when slavery was in full effect most people did physical labor, plenty of white people in this country at the time were involved in settling the frontier and building cities and towns.  But White people were not selectively bred by slave masters. Slave owners would intentionally breed their biggest and strongest male and female slaves to produce better workers. They were selectively bred to be bigger, stronger and for stamina to make better workers. Just like you would do with any other livestock, which is basically what the majority of Black slaves were used as, livestock. African-Americans are freaks of nature, they are like Frankenstein's monster, White slave masters created them. That's why Black Americans tend to be on average much more athletic than Black Africans. These Blacks who dominate many sports today are mostly Black Americans and not real Black Africans, except for those Kenyans who are good runners because they have no vehicles and have to run everywhere they go while being chased by lions :p