November 24, 2009 will mark the 150th anniversary of the publication of Charles Darwin's On the Origin of Species, and scientists have already started the celebrations. Last week, for example, the University of Chicago hosted a series of talks by some of the top evolutionary scientists working today. Among those delivering lectures was paleontologist Paul Sereno.
According to notes posted by blogger PZ Myers, early on in the discussion Sereno puzzled over why Darwin neglected many fossils, and dinosaurs in particular, in his most famous book. Dinosaurs are very closely related to evolutionary science today, but Darwin appeared to ignore them. Why?
Sereno posited that Darwin's tense relationship with the Victorian anatomist Richard Owen, who coined the term "dinosaur" in 1842, kept him from talking about dinosaurs. Owen was a brilliant scientist but his cantankerous attitude was well-known. Worse than that, even though Owen was an evolutionist he disagreed strongly with Darwin over what the mechanism of evolution was, and his criticism of Darwin has fooled many people into thinking that Owen was a young-earth creationist.
The problem is that there is virtually no evidence to show that Darwin ignored dinosaurs because he was afraid of big, bad Richard Owen. In all of Darwin's correspondence with other scientists there is almost no mention of dinosaurs at all, and when Darwin later addressed dinosaurs he did so to show how little was known about the fossil record.
As I wrote earlier this year, during Darwin's time dinosaurs were enigmatic creatures. Not only were they very different from living reptiles, they were very different from each other, and most of the first specimens that were discovered were extremely fragmentary. It was not until 1858, the year before On the Origin of Species was published, that the relatively complete skeleton of Hadrosaurus was found in New Jersey. This discovery, along with several others, made scientists start to reconsider what dinosaurs looked like right as Darwin's book was being published.
I think Darwin was wise to leave dinosaurs out of On the Origin of Species. At the time of his writing, only a few genera were known from incomplete specimens, and no one would be able to tell what they had evolved from or if they left any living descendants. The seemingly aberrant forms of the dinosaurs hinted that there was more yet to be found in the fossil record, but they could not yet be pressed into the service of holding up the evolutionary mechanism Darwin was proposing.
Yet this, too, is a hypothesis. Darwin is long dead, and we cannot ask him why dinosaurs did not figure into his work. Still, I think the view presented here more closely represents Darwin's concerns that what Sereno has proposed.