Origin of Bird Flight: A Physics Viewpoint Available to Purchase

The debate over the origin of bird flight dates back over 100 years. Over the last century two opposing viewpoints have emerged. The first claims that flight originated by running along the ground and then leaping and flapping—this is called the “ground-up” theory.¹ The second claims that flight originated from the trees—from jumping out of trees and gliding—and is called the “tree-down” theory.² Recently, Long et al. proposed a new theory—“flutter-gliding”—that combines features from both of these previous theories.^3–5 This paper will discuss all three of these theories of the origin of bird flight in terms of Newton's second law of motion and provides a simplified version of a series of articles published by Long et al.^3–5 We believe this material is a wonderful application of Newton's second law of motion that is appropriate for both high school and college introductory physics courses, and leads naturally into a discussion of the physics of gliding, flying, and sprinting.