Voltaire’s Philosophical Dictionary includes a dialogue between the Philosopher and Nature, in which the Philosopher poses the following question:
We are curious. I want to know how being so crude in your mountains, in your deserts, in your seas, you appear nevertheless so industrious in your animals, in your vegetables?
Nature’s reply is to dismiss the apparent difference (“Do you not know that there is an infinite art in those seas and those mountains that you find so crude?”), but the Philosopher’s question is a good one. However impressive seas and mountains (and stars, and everything else in the universe) may be in their own way, none of it even begins to compare with the astonishing complexity of the biological world. Why this chasm?
Darwinism answers Voltaire’s question. Natural selection is ultimately the only way extremely complex things can come into being, and so every extremely complex thing in the world is created, either directly (organisms) or indirectly (technology created by organisms), by replicators such as DNA molecules. The chasm is between things that were created by replicators and things that were not.
Creationism, on the other hand, can’t really answer the question. (Paley noticed how similar an animal is to a watch and how different it is from a rock — and concluded that animals must have been made by the same guy who invented rocks!) Of course there’s no reason why God can’t have created simple things as well as complex, but creationism doesn’t know what do with the obvious correlation between complexity and reproduction. In nature we find very complex things that reproduce and far simpler things that don’t. Conspicuous by its absence is anything truly analogous to the human technology typified by the watch — very complex things that don’t reproduce. To a creationist, there’s no obvious reason for this; it must just be how God decided to do things. From a Darwinian point of view, though, the absence of true “watches” in nature is precisely what we ought to expect.