I run ultramarathons and whether true or not, we sometimes joke about this. We'd say that the typical Springbok would fall down from exhaustion after 30 km and that's why we runners hit that metaphorical wall after 31 km; we evolved because we needed to outrun the gazelle by only a bit. From there on, it's a tough grind to complete the race.

Very tongue-in-cheek, but too good of a story not to tell.