I just heard about the coolest study. I don't have a citation, but the gist is that during the 1968 Olympics, it was discovered that a high percent of American Blacks on the US team carried one copy of the gene for sickle-cell anemia. It turned out that one copy of the gene improves oxygen transport to fast-twitch muscles, which lets them twitch faster.
If this is true (and I heard it from someone I trust), a side effect of having one copy of the gene is that it makes you better at sports that require fast-twitch muscles. (Of course, a side effect of two copies is that you die young, but not from malaria.)
Notice that, although this was discovered after noticing the number of US Black athletes with the gene, it would affect anyone with that gene, meaning a fair number of people with ancestry from places where malaria is endemic. You'd expect Saudis, for example, to do well at sprints.