Are you more of a dog or a ferret? [news]

The science behind runner's high could prove the vital place of exercise in the evolutionary history of humankind. Ferrets don't often figure in studies of exercise, perhaps because they don't exercise much. They slink like fog through tunnels, sprint briefly over open ground and spend much of their time sleeping. They are, in biological terms, what's called a non-cursorial species, meaning they are reluctant and lousy distance runners. Which is why they were ideal subjects for an experiment conducted at the University of Arizona in Tucson looking at whether humans and other species evolved to like running. Many anthropologists and distance runners believe that running guided the evolution of early humans. We ran in search of dinner and to flee from predators. But running is costly, metabolically. It incinerates energy. It can also cause injury. A twisted ankle would have removed your typical early human from the gene pool.