Todd Oakley reports on a dust-up over at Panda’s Thumb in which a commentator is not convinced that eyes evolved, in large part because the specific details of the early origin of the phototransduction pathway have yet to be worked out. Not surprisingly, responses have pointed out that the gaps are getting smaller and smaller and that a lot is known about how phototransduction may have arisen from precursors in other systems through duplication, co-option, and the various processes discussed in this paper.

I think this debate misses a much larger and more significant point. Darwin suggested that eyes evolved in the Origin, published 150 years ago. This was before even the basics of heredity were generally understood. It was before the discovery of DNA. Before the elucidation of the structure of DNA. Before the rise of molecular biology. Before the advent of phylogenetics. Before evolutionary developmental biology. Before genome sequencing.

And yet, through the emergence of all these major new sources of data, not a single reliable observation in any of these fields has contradicted the general hypothesis that eyes are the product of evolutionary mechanisms. Quite the opposite, as the picture of how this probably occurred in different lineages is become increasingly clear thanks in large part to this rapidly expanding body of knowledge. Gaps remain, of course, which is why it’s an intriguing field of inquiry. But the notion of waiting until every last detail is known before accepting the basic historical reality badly misinterprets the nature of science and scientific evidence.