Passage:
For over a century, debate regarding the origin of avian flight centered on two diametrically opposed hypotheses: the arboreal ("trees-down") model, which posited that protobirds climbed trees and glided down, and the cursorial ("ground-up") model, which argued that terrestrial bipeds ran and leaped to capture prey, eventually developing powered flight. This long-standing dichotomy began to dissolve with Ken Dial's introduction of the wing-assisted incline running (WAIR) hypothesis. Dial observed that young chukar partridges use incipient, feathered wings not to generate lift for airborne flight, but to produce aerodynamic traction that allows them to scale steep, near-vertical substrates. By demonstrating how rudimentary aerodynamic structures confer an immediate adaptive advantage in terrestrial locomotor performance, WAIR provided a crucial mechanical bridge between ground-based movement and aerial maneuverability. Consequently, rather than viewing cursorial and arboreal behaviors as mutually exclusive evolutionary paths, contemporary paleontologists increasingly recognize that early theropods utilized wing precursors to negotiate complex topography���thereby reframing the origin of flight as an integrated functional transition rather than a simple binary choice between leaping from trees or running on flat ground.
Based on the passage, which of the following statements accurately characterize the primary purpose and central thesis of the text? Select all that apply.
- It explains how a novel biomechanical framework helps synthesize two historically opposing evolutionary models.Answer
- It posits that early aerodynamic structures likely conferred locomotor advantages for incline navigation before enabling powered airborne flight.Answer
- CIt demonstrates that the cursorial model must be completely discarded in light of empirical evidence gathered from modern avian species.
- DIt asserts that Ken Dial's experimental findings definitively resolve all ongoing debates surrounding theropod classification.
- EIt provides a detailed physiological analysis of the muscular mechanisms that generate airborne lift during flapping flight.