[lacrew]

“There is zero record of slaveholders intentionally breeding humans for traits”

http://en.wikipedia.org/wiki/Slave_breeding_in_the_United_States

[muawiyah]

The African population in North America was, as a practical matter, miniscule as late as the invention of the cotton gin in 1794.

Then it grew ~ but by 1865 slavery was all over. You really don't have much chance in a 71 year period to 'breed' humans. Their time to maturity is simply too great to be able to select traits.