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Olshevsky maintains the comprehensive online Dinosaur Genera List. He is known as the originator of the Birds Came First hypothesis in the descent of birds debate, which states that all dinosaurs are the descendants of small, arboreal and perhaps flying ancestors.
Olshevsky is part of a collaborative effort to recognize and standardize terms used to describe uniform 4-polytopes and uniform polytopes, the analogues of uniform polyhedra in four and higher dimensions.
George Olshevsky was born on June 12, 1946, and for many years (particularly the 1960s to the 1980s) "collected Marvel Comics and compiled the Official Marvel Comics Index for Marvel," owning for 14 years "the world’s only complete collection of Marvel superhero comics that extended all the way back to Marvel’s first comic book, Marvel Comics #1, October–November 1939". While compiling the Marvel Indices, he "produced some 60 fully illustrated books, totaling more than a million and a quarter words," producing indices to all the major Marvel Superheroes (including Avengers, The Amazing Spider-Man, Fantastic Four, Marvel Team-Up, etc.) mostly between 1976 and 1988, although he notes that beyond the 1976 date, he "never did manage to index every single Marvel superhero comic, just the more popular runs". Since that time, he does not think of himself as an active comics collector, although he notes that the impulse to index remains - his Dinosaur Genera List is "essentially an index to all the dinosaur names"; his Uniform Polychora website is "an index to all the convex uniform polychora" and his day job (as of the late 1990s/early 2000s) is freelance book indexing.
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The Birds Came First-hypothesis ("BCF") is a radical expansion of the possibility that some dinosaurs are secondarily flightless, arguing that all dinosaurs are "postvolant". The hypothesis, or ecomorphological and phylogenetic scenario, was developed by Olshevsky in the early nineties. Shortly after reading Gregory S. Paul's Predatory Dinosaurs of the World, Olshevsky realized that the arguments expounded there for the secondarily flightlessness of the Maniraptora might well be adapted to argue for the same condition in all Theropoda, indeed in all Dinosauria.
"BCF" accepts the close relationship between dinosaurs and birds, but argues that, merely given this relationship, it is just as likely that dinosaurs descended from birds as the other way around. In this case the term "birds" refers to a morphological state, not to Aves as they have been cladistically defined. Olshevsky does not claim that the branch leading to modern birds split off from other dinosaurs very early; in fact precisely the opposite: he thinks that Aves is but the most derived expression of a vast diversification of flying dinosaurs all through the Jurassic.
BCF admits that most dinosaurs found are large and very derived in morphology compared to a hypothetical flying ancestor, and it also accepts the results of cladistic analysis connecting these large species into a cladogram, suggesting that the intermediate forms were also large. BCF could have avoided this problem by claiming that just a very basal form was volant and all subsequent forms large. Instead Olshevsky resorted to a far more radical position by emphasising the point that a cladogram doesn't logically imply the morphology of its intermediate steps. He claimed, basing himself partly on Cope's law, that there was a hidden stem lineage of small arboreal forms that during the Mesozoic was the real engine driving dinosaurian evolution, generating time and again larger ground-dwelling species. The smallness and arboreality of the forms was used to explain the fact that they rarely left a trace in the fossil record. Of course being small and arboreal doesn't imply the capacity to fly and Olshevsky allowed his hypothesis to diverge in three subhypotheses: the weakest was that the stem line consisted of small tree-living species; the stronger was that these could glide; the strongest that they possessed full powered flight.
BCF has not found acceptance among professional paleontologists. It was only published twice, once in a magazine, Mesozoic Meanderings, which Olshevsky himself produced, and once in the popular-science magazine Omni. Paul perfunctorily dismissed the hypothesis in his Dinosaurs of the Air; in the peer-reviewed literature it is never even mentioned as such. However this does not mean the hypothesis has been completely ignored by professionals. Olshevsky is a well-known figure among dinosaur enthusiasts in the USA and has been for many years a very active participant in the various internet fora dedicated to the study of dinosaurs. This has led to much debate about BCF. The main objections from the professional side are that the scenario as a whole is too vague to be testable and that the empirical support for the most interesting subhypothesis — full flight capacity — is poor. Only for the group of the Tetanurae, which are already quite derived theropods, are there some slight indications, and these can be explained as exaptations. Because of the many convergences needed, BCF is also not very parsimonious when analysed from a cladistic point of view, as it implies that flight was lost many times. The parsimony problem would only be remedied if many flying forms would be found basal to the various groups. Current paleontological consensus is that dinosaurs started as, and largely remained, ground-dwelling forms, that most major branching points in Mesozoic dinosaurian phylogeny were not volant and that it were only the members of the derived dinosaurian clade Maniraptora that took to the trees — and to the air — during the Jurassic.