The origin of novel phenotypes has challenged evolutionary biologists since the time of Darwin. Darwin’s theory of evolution provides an explanation for how natural selection

evolutionary biologists since the time of Darwin. Darwin’s theory of evolution provides an explanation for how natural selection eliminates the less fit phenotypes, but leaves open the question of how novel phenotypes arise. The origins of animal flight are particularly important evolutionary transitions because aerial locomotion is thought to be a significant factor in the diversification of birds (Padian and Chiappe, 1998), bats (Thewissen and Babcock, 1992) and insects (Kingsolver and Koehl, 1994; Carpenter and Richardson, 1985; Wootton, 1981). The rigorous evaluation of any hypothesis of the origin of flight requires a comparative study between basal non-flying species and derived flying species. Among the birds and bats, two of the most famous and capable flying vertebrate lineages, the only non-flying species available for study are either extinct fossils or extant species that have secondarily lost the ability to fly, such as penguins or ostriches.