What if dinosaurs didn’t evolve to become birds? e! Science News reports that a new study published in the Proceedings of the National Academy of Sciences suggests dinosaurs might actually have evolved from birds and not the other way around, as is commonly believed. Oregon State University zoology professor John Ruben offers commentary about the study, which tested a new specimen of raptor fossil discovered in 2003. The PNAS study concluded that the “small, feathered species must have been a ‘glider’ that came down from trees.”

The general and long-held belief that raptors and other ground-dwelling dinosaurs eventually became birds is brought into question by the research, which Ruben says offers sound evidence that birds eventually became certain types of dinosaurs. For instance, the velociraptor so prominent in Jurassic Park might actually have been a flightless bird.

Analysis of the feathers on the “microraptor’s” four limbs suggests that the dinosaur probably couldn’t have taken off for ground-up flight, but were probably gliding from trees, “somewhat like a modern-day flying squirrel.” Ruben says this analysis makes it improbable that dinosaurs one day took to the skies but, rather, that birds one day touched down and stayed put, eventually becoming dinosaurs.

According to Ruben, the “who came first” dino/bird debate is far from over. Oregon State University has been conducting dinosaur evolution research for 20 years and Ruben suggests that birds and dinosaurs might “have had an ancient, common ancestor … but they evolved separately on their own path.”

The PNAS study combined with Ruben’s work and a study from Florida State University give weight to the new theory that birds were the predecessors. Ruben’s own work identified certain bones and muscles affecting lung capacity for long flight that are missing in certain ground-dwelling dinosaurs. According to e! Science News, other studies have identified bird fossils that are actually older than the dinosaurs they theoretically descended from. Ruben ends his commentary in PNAS with a critical eye toward “current notions” of evolution and the fossil record, urging us to continue to question beliefs about the evolutionary process of dinosaurs.