Individuals of West African-origin have longer legs than European-origin athletes, which means their belly buttons are three centimeters (1.18 inches) higher than whites', said Bejan.
That means the black athletes have a "hidden height" that is three percent greater than whites', which gives them a significant speed advantage on the track.
"Locomotion is essentially a continual process of falling forward, and mass that falls from a higher altitude, falls faster," Bejan explained.
In the pool, meanwhile, whites have the advantage because they have longer torsos, making their belly buttons lower in the general scheme of body architecture.
"Swimming is the art of surfing the wave created by the swimmer," said Bejan.
"The swimmer who makes the bigger wave is the faster swimmer, and a longer torso makes a bigger wave. Europeans have a three-percent longer torso than West Africans, which gives them a 1.5 percent speed advantage in the pool," he said.
Asians have the same long torsos as Europeans, giving them the same potential to be record-breakers in the pool.