Tolkien and Darwin Among the Machines

In The Letters of J.R.R. Tolkien, I found the following passage. He is writing to his son Christopher, who was training to be an air force pilot in Africa during World War II:

I wonder how you are getting on with your flying since you first went solo-- the last news we had of this. I especially noted your observations on the skimming martins. That touches to the heart of things, doesn't it? There is the tragedy and despair of all machinery laid bare. Unlike art which is content to create a new secondary world in the mind, it attempts to actualize desire, and so to create power in this World; and that cannot really be done with any real satisfaction. Labour-saving machinery only creates endless and worse labour. And in addition to this fundamental disability of a creature, is added the Fall, which makes our devices not only fail of their desire but turn to new and horrible evil. So we come inevitably from Daedalus and Icarus to the Giant Bomber. It is not an advance in wisdom! This terrible truth, glimpsed long ago by Sam Butler, sticks out so plainly and is so horrifyingly exhibited in our time, with its even worse menace for the future, that it seems almost a world wide mental disease that only a tiny minority perceive it. Even if people have heard the legends (which is getting rarer) they have no inkling of their portent...Well, I have got over 2 thousand words onto this flimsy little airletter; and I will forgive the Mordor-gadgets some of their sins, if they will bring it quickly to you... (7 July 1944, letter 75)

Christopher seems to have pointed out in a letter some contrast between the natural flying of the martins (swallows that fly with their mouths open to skim insects) and the laborious difficulty of flying and taking care of his own air force planes. His father was reminded of the main theme of The Lord of The Rings, which he was deep in the middle of writing at that point (and in fact he considered Christopher his main audience for the work). The idea is that our attempt to improve the world through creating technology is doomed to bring about our destruction in the end. This apocalyptic vision of the future of automation he felt had been captured in the writings of Samuel Butler-- referring, surely, to Darwin Among the Machines. Tolkien is, as far as I am aware, the only reader before the 1950s who ever took Butler's story as a serious warning about a possible future, rather than just a silly parody. I would love to be able to read Tolkien's own vision of an apocalyptic dystopian future where the machines have risen.
Later, in January 1945, upon learning that the Russians were 60 miles from Berlin, he writes about the tragedy of the destruction of Germany ("be it 100 times merited") and then writes,

Well, the first War of the Machines seems to be drawing to its final inconclusive chapter -- leaving, alas, everyone the poorer, many bereaved or maimed and millions dead, and only one thing triumphant: the Machines. As the servants of the Machine are becoming a privileged class, the Machines are going to be enormously more powerful. What's their next move? (January 30, 1945, Letter 96)

He writes upon learning of the atomic bomb (again in a letter to Christopher):

The news today about 'Atomic bombs' is so horrifying one is stunned. The utter folly of these lunatic physicists to do such work for war purposes: calmly plotting the destruction of the world! Such explosives in men's hands, while their moral and intellectual status is declining, is about as useful as giving out firearms to all inmates of a gaol and then saying that you hope 'this will ensure peace.' But one good thing may arise out of it, I suppose, if the write-ups are not overheated: Japan ought to cave in. Well, we're all in God's hands. But he does not look kindly on Babel-builders. (9 August 1945, letter  102)

Later he writes to his publisher Unwin:

You can make the Ring an allegory of our own time, if you like: an allegory of the inevitable fate that awaits all attempts to defeat evil power by power. But that is only because all power magical or mechanical does always so work. (31 July 1947, letter 109)

(C.S. Lewis shared many of these concerns, by the way. There is the 'Deplorable Word' that destroyed the world of Charn in The Magician's Nephew and one of the best warnings about the danger of messing around with sentients' utility functions I have ever read in The Abolition of Man.)