Yeh I watched it, and it was a little more thought provoking than I anticipated.
These shows have been done before, Colin Jackson did one a couple of years ago on BBC3 - (it was terrible).
The issue I always had with the idea that Caribbeans/African-Americans are physically superior is because of slave trade/selective breeding etc, was that I felt it was something that white men grasped at to rationalise their physical inferiortity - and then claim, "...But hey, it's all down to us."
For example, one could go to the source of where slaves were captured - West Africa....for the most part, people from this part of the world have the same 'superior physical genetics'. So this puts a huge hole in the theory of 'selective breeding/slave trade etc.
If sprinting was the 'national sport' of Ghana/Nigeria/Senegal/Gambia etc etc. we'd have many more champions from that part of the world too.