Darwin and Gray

Charles Darwin once wrote to Asa Gray, "The eye to this day gives me a cold shudder, but when I think of the fine known gradation my reason tells me I ought to conquer the odd shudder."

This quotation is well known. But Matt Ridley, a columnist for the weekend edition of the Wall Street Journal, devoted last week's column to Darwin and the eye, and he has me thinking abou the  matter anew, too. The eye was presumably giving Darwin shudders because it is a very complex organ. One has a tough time imagining any single "random variation" that would give a newborn of some mammalian breed a pair of eyes that its parents had not had. THAT would be an implausible jump.

Thus, the eye must have come about through increments. Yet it seems difficult to construct a chain of slow increments from no sight at all to the full carbon-based cameras that mammals suggest.  As Ridley asks rhetorically, "What use is half an eye?" I was going to write something more here about the eye and its evolutionary biology, but you can find plenty of material elsewhere. Such as here. My thoughts have headed off in a different direction even since I started work on this entry.

I asked myself: who was Asa Gray? Ridley simply describes him as an American botanist. Why would Darwin have written to a botanist about the eye?

It would surely be more germane to mention that Gray, founder of the botany department at Harvard University, was also a personal friend of Darwin's. Also, Gray became the author of Darwiniana, an influential book published in 1876, which you can read here, courtesy of Project Gutenberg.

One of the themes of Gray's book was the effort to reconcile natural selection with a theistic view of the world, to make the point that: "One, indeed, who believes, from revelation or any other cause, in the existence of such a Creator, the fountain and source of all things in heaven above and on the earth beneath, will see in natural variation, the struggle for life, and natural selection, only the order or mode in which this Creator, in his own perfect wisdom, sees fit to act."