The initial question presented at the beginning of the article pertains to the evolution of flight in regards to evolutionary advantage during the intermediate stages. There are two rival theories; the”tree down” hypothesis as well as the “ground up” hypothesis that support conflicting ancestral behavior that eventually transitioned to modern flight. Dial’s interpretation of his data, specifically the correlation between the WAIR facilitating movement on coarse surfaces, such as tree bark, as well as the change in the birds’ center of gravity while performing WAIR, both support the ground-up hypothesis as these qualities seem to be an escape mechanism for terrestrial birds. In addition, Dial goes on to suggest that proto-birds, such as archaeopteryx, had bone structure to support antero-posterioral movement, which is ideal for the movements necessary for WAIR utilization. Furthermore, he proposes that wing-angle adjustment used for varying levels of incline could have also been used as a tool for controlled descent and body manipulation while in mid air, which could have also contributed to the eventual evolution of flight.
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