Among the many recurring themes on this blog, the evolution of birds from feathered maniraptoran dinosaurs is probably the most prevalent. Hardly a month goes by without a new study relevant to this major evolutionary transition, and as paleontologists discover more they continue to find that many traits once thought to be exclusive to birds were widespread among dinosaurs. Yet this understanding has only coalesced within the last 15 years. For over a century, the early evolution of birds remained a mystery, and numerous suggestions were made about avian origins.

For much of the past 150 years, how the first birds evolved and what sort of animals they originated from depended upon whom you asked. The English anatomist Thomas Henry Huxley proposed that there was a step-by-step transition from small dinosaur-like creatures through flightless birds (like ostriches) to flying birds, whereas his colleague Harry Govier Seeley vehemently disagreed and believed that birds had evolved from pterosaurs. The idea that birds had an aquatic origin—either evolving from swimming dinosaurs or becoming adapted to life in the sea before taking to the air—was also espoused by several naturalists. But one of the most amusing ideas I have yet encountered was an article by W.T. Freeman printed in an 1897 issue of Gentleman's Magazine.

Freeman had developed his own peculiar way of looking at the history of life. A creationist, but of a different sort than today's religious fundamentalists, he thought that there was a clear succession of organisms over time in which there were distinct species incapable of evolving into something else. As evidence for this, Freeman cited the fact organisms created near-perfect copies of themselves through reproduction. No organism gave birth to a different species, and even when two species interbred—an inappropriate interaction Freeman deemed "perverted"—the hybrid never became established as a new species.

Within this creationist system, Freeman believed he had found an explanation for Archaeopteryx. Recognized by many naturalists as an early bird with reptilian characteristics such as teeth and a long, bony tail, Archaeopteryx was regularly used as evidence that birds had indeed evolved from reptiles. ("Everything has, or has had, a definite purpose in life," Freeman wrote, "and the archaeopteryx lived its life in order to bring bliss to the soul of the evolutionist.") But Freeman took a different view. The mish-mash of bird and reptilian characters indicated that Archaeopteryx was nothing more than a sign of ancient indiscretions:

I suggest that in the earlier days there were ill-developed, low-typed, wallowing birds, also some highly developed reptiles. Perverted sexual instinct exists now, why not then, and as a result of this, why has not the archaeopteryx been an anomalous false hybrid that has been incapable, like other mongrels, of reproducing its kind?

When I first read this, I had to wonder if the essay was meant as some kind of joke or satirical jab at the science of evolution. How could anyone seriously believe that Archaeopteryx was the product of a union between birds and reptiles? Yet Freeman's essay is serious from start to finish, and I was able to find at least one other essay by him about his off-kilter creationist beliefs.

Frustratingly for Freeman—but fortunately for our understanding of the natural world—the idea that Archaeopteryx was the monstrous offspring of reptile and bird never took off. The animal truly was the first feathered dinosaur ever found, and, even though it took over a century to arrive at this view, the multiple Archaeopteryx specimens discovered so far remain important to ongoing research about the evolution of birds.