The Arboreal and Cursorial Hypotheses of the Flight Origin Research Paper - 1

The Arboreal and Cursorial Hypotheses of the Flight Origin - Research Paper Example The arboreal hypothesis (also known as the ‘tree down’ hypothesis) refers to the idea that dinosaurs first gained flight by jumping from trees and acquiring flight as an evolutionary mechanism to avoid fatal accidents from this method. This hypothesis seems ‘intuitive’ because ‘flight evolving from an arboreal gliding stage would seem to be relatively easy’ (Padian & Chiappe, 1998, p15) and because the force of gravity ‘helps rather than hinders’ (Lewin, 1983, p38). Some studies, such as that of Feduccia (1993) suggest that the shape of the manus (the ‘hand’ portion of the forelimb) and the pes (the ‘foot’ portion of the hindlimb) of the Archaeopteryx exhibit evidence of perching, tree-dwelling and trunk-climbing due to the curvature of these anatomical elements. However, since this paper was published, another specimen of Archaeopteryx has been discovered (known as the Thermopolis specimen) which has almos t complete pes, and thus there is now mounting evidence that the hallux (first digit of the pes) did not display curvature necessary for perching (Mayr et al., 2007). If we consider the Archaeopteryx as arboreal, it is important to understand how and why a flight would have developed in this way. The original theory as stated by Othniel C. Marsh in the late 19th century was that Archaeopteryx would use wings as a balancing mechanism during leaps between trees, utilizing a gliding model to conserve energy. A common refutation to this point is that Archaeopteryx would utilize energy to climb trees (Mayr et al., 2007) but the terrestrial running would have taken more and as such gliding would be an evolutionary advantage (Feduccia, 1993). This, if taken as proof of the ‘intermediate gliding stage’ (Lewin, 1983, p38) that is so necessary for supporting the arboreal hypothesis, would help solve this challenge to evolutionary biology. A major problem with using Archaeopteryx as proof of the arboreal hypothesis is that it possessed very long, sharp claws or talons.