Hello,
A lot of people have the idea that slave owners bred their slaves for strength, mating the bigger and stronger ones to produce bigger and stronger children, and that this was a frequent occurrence in American slavery. Anyway, my question is, is there any evidence that this type of selective breeding of slaves occurred, and how widespread was the practice, if it did?
On the one hand, it makes anecdotal sense -- most of the black guys I know are more "jacked" and can put on muscle more easily than your average white guy. From what I've read about slavery, though, slaves seemed to pick who they married without the masters caring much or giving any input. I've never read about slaveowners pairing slaves up to produce a specific type of child.
One possibility could be that the weaker slaves died early anyway, either on the ships or shortly after arriving, so the black people who lived long enough to pass on their genes tended to be stronger. I don't want to speculate any more though, since I don't know. Any input from someone who does would be appreciated.
There certainly is evidence that the kind of practice you described did occur, at least in the antebellum South; some slave testimonies do discuss occasions where sexual unions were pre-arranged or imposed upon slaves with the apparent goal of having particular slaves to have children together. In an historical record that is otherwise rich with allusions or outright testimonies to systematic sexual abuse by white owners and their intermediaries though, such accounts are exceedingly rare; we have no reason to believe that this was by any means a wide-spread phenomenon. Certainly 'softer' controls on sexual activity and reproduction were much more common, like the practice of some owners limiting their slaves to only take partners within their own estate - but that was a practice motivated more by concerns of economy (i.e., because a slave child is the property of their owner's mother, ideally you want as many children as possible being born to women on your own estate, rather than a plantation owned by someone else) rather than breeding interests. Sexual abuse of black slaves by white people, particularly male owners, was a much, much more common aspect of slavery - with the products of such unions being slaves. Again though, this isn't anything to do with forced breeding for particular characteristic suited for labour.
With regards to your speculative remarks, it is of course impossible to generalise meaningfully from anecdotal observations. But differences you perceive, if we did take that they are universal, probably have much more to do with the complex intersection of genetic and environmental factors than the experience of slavery. Death on slave vessels would have been largely arbitrary; I would suggest that a stronger immune system would have been the main genetic advantage in surviving the trip to the New World.