Seems like C.S. Lewis never had a whole lot to say on the evolution topic. I found this article interesting nonetheless.
… It was sometime in this period when, at a dinner party where the guests included Helen Gardner, the topic was raised as to whom one would like to meet in heaven. One guest suggested Shakespeare while another suggested the apostle Paul, but Lewis said that he would like to meet Adam. He gave as his reasons:
Adam was, from the first, a man in knowledge as well as in stature. He alone of all men ‘had been in Eden, in the garden of God, he had walked up and down in the midst of the stones of fire’. He was endowed, says Athanasius, with ‘a vision of God so far-reaching that he could contemplate the eternity of the Divine Essence and the coming operation of His Word’. He was ‘a heavenly being’ according to St. Ambrose, who breathed the aether and was accustomed to converse with God ‘face to face’.
Helen Gardner, a church-goer with a deep interest in the seventeenth century English metaphysical poets, ventured to suggest that Adam, if he existed, would be a Neanderthal ape-like figure whose conversation would hardly be interesting. Apparently, Lewis responded in a gruff voice: ‘I see we have a Darwinian in our midst.’