Meeting Abstract
Bipedal humans, like dogs and a few other cursorial mammals, are thought to have been selected for endurance running. As to be expected, the ability to run long distances requires the ability to inspire large amounts of air for sustained periods of time. During sustained high aerobic activities, humans can be required to breathe as much as 6.1-6.9 L of air/min per kilogram of body mass, and only a few other running adapted (cursorial) mammals, including dogs, wolves, camels and horses, are capable of such sustained aerobic capacity. We experimentally test the hypothesis that humans and dogs rely on thoracic volume changes to increase tidal volume during running to a greater extent than goats, a quadrupedal, non-cursorial species. While all three species use diaphragmatic breathing to increase tidal volume in order to augment respiration with increasing oxygen demand, dogs also use increased dorsoventral expansion of the thorax, and bipedal humans use both dorsoventral and mediolateral expansions of the thorax. 3D analyses of joint morphology across four mammalian orders also show that cursorial species independently evolved more concavo-convex costovertebral joint morphologies that allow for increased rib motion and greater thoracic expansion and contraction. Evidence for similarly derived concavo-convex costovertebral joints in Homo erectus corresponds with other evidence for the evolution of endurance running in the genus Homo.
