Its called Alpha-actinin-3, or ACTN3 for short, and it is a protein that is encoded within humans. How exactly does this make those of African descent more athletic? The amount of ACTN3 determines the amount of endurance we have and the speed at which we can sprint.
What causes it to affect athleticism is when it has a mutation, which generally applies to 20-50% of the population. Studies have linked those who do not have the mutation to a fiber twitch within the body that causes much faster reflexes.
Generally, Africans have the lowest amount of ACTN3 mutation in their system, which allows them to be less restricted while exercising. In contrast, those of Asian descent generally have the highest levels of the mutation. After the amazing running times by Usain Bolt in the Olympics, extensive tests were done on Jamaicans in particular and scientists found that around 70% of the Jamaican population is naturally more athletic because of ACTN3.
The studies have not been without controversy, with some scientists saying that there are factors beyond race that determine athletic potential. As with a lot of these studies, it’s important to remember that they deal in probabilities and likelihoods. In this case, just because on race is more likely to have this mutation, doesn’t mean that no other race is precluded from being athletic, or that there are other factors that can make someone else also be athletic.