A fundamental avian wing-stroke provides a new perspective on the evolution of flight

摘要: The evolution of avian flight remains one biology's major controversies, with a long history functional interpretations fossil forms given as evidence for either an arboreal or cursorial origin flight. Despite repeated emphasis on the 'wing-stroke' necessary avenue investigation addressing flight, no empirical data exist wing-stroke dynamics in experimental evolutionary context. Here we present first comparison kinematics primary locomotor modes (descending and incline flap-running) that lead to level-flapping juvenile ground birds throughout development. We offer results are contrary both popular perception inferences from other studies. Starting shortly after hatching continuing through adulthood, use confined narrow range less than 20 degrees , when referenced gravity, directs aerodynamic forces about 40 above horizontal, permitting 180 direction travel. Based our results, put forth ontogenetic-transitional wing hypothesis posits incremental adaptive stages leading correspond behaviourally morphologically transitional observed ontogenetic forms.