Maywa Montenegro in Seed Magazine:
Ann Trason, Scott Jurek, Matt Carpenter. These are the megastars of ultra-distance running, athletes who pound out not just marathons, but dozens of them back-to-back, over Rocky Mountain passes and across the scorching floor of Death Valley. If their names are unfamiliar, it’s probably because this type of extreme running is almost universally seen as a fringe sport, the habit of the superhumanly fit, the masochistic, the slightly deranged.
But a handful of scientists think that these ultra-marathoners are using their bodies just as our hominid forbears once did, a theory known as the endurance running hypothesis (ER). ER proponents believe that being able to run for extended lengths of time is an adapted trait, most likely for obtaining food, and was the catalyst that forced Homo erectus to evolve from its apelike ancestors. Over time, the survival of the swift-footed shaped the anatomy of modern humans, giving us a body that is difficult to explain absent a marathoning past.
Our toes, for instance, are shorter and stubbier than those of nearly all other primates, including chimpanzees, a trait that has long been attributed to our committed bipedalism. But a study published in the March 1 issue of the Journal of Experimental Biology, by anthropologists Daniel Lieberman and Campbell Rolian, provides evidence that short toes make human feet exquisitely suited to substantial amounts of running.
More here.