The origin of birds has been discussed since the discovery and description of Archaeopteryx in Bavaria in 1861. By 1868, Thomas Henry Huxley realized its significance as a connecting form, which illustrated how birds might have evolved from dinosaurs. A century later John Ostrom articulated a convincing modern case for the origin of birds from theropod dinosaurs. Recent cladistic analyses of theropod, bird and bird-like fossils seem to confirm this scenario of bird origins. The purpose of this paper is to examine both the philosophic principles and the practice of cladistic analysis upon which the dinosaur-bird link is currently based. Cladistics is based on a Popperian philosophy that emphasizes the hypothetical nature of all knowledge. Such a philosophy seems more suitable for analyzing idealized characters unrooted in time or space rather than real objects. A philosophy of critical realism seems more congenial for analysis of evolutionary biological individuals having a real history. Cladistics uses parsimony as a first principle, which may be rejected on the grounds that nature is prodigal in every regard. Parsimony based on morphology suffices only when there are no other data sets to consider. Cladistics systematically excludes data from stratigraphy, embryology, ecology, and biogeography that could otherwise be employed to bring maximum evolutionary coherence to biological data. Darwin would have convinced no one if he had been so restrictive in his theory of evolution. The current cladistic analysis of bird origins posits a series of outgroups to birds that postdate the earliest bird by up to 80 million years. This diverts attention from the search for real bird ancestors. A more coherent analysis would concentrate the search for real avian ancestors in the Late Jurassic.
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