A former, recovering Young Earth Creationist asks about the theory of evolution. They abandoned YEC because of its claim that the Earth is 6,000 years old. They’re convinced that the Human Genome Project proves the theory of evolution – but they also state that they have “found it difficult to find good evidence for evolution”. They ask for proofs of evolution that readers found most convincing and for resources to study those proofs. Below is my response.

From what you describe, it might be a little early to say you’re “convinced” of the theory of evolution. Which is why you’re asking for proof.

You may be disappointed to hear that there is no proof. Scientific theories can never be proven true (see Karl Popper’s The Logic of Scientific Discovery). They are guesses rich in consequences and predictions that we could not possibly test exhaustively. What we can say about evolution is that it has survived great amounts of potentially devastating criticism and experiments and it is the only viable explanation that is left standing. So far. Maybe tomorrow somebody finds fault with it; maybe the day after, somebody proposes an even better theory. The Human Genome Project does not prove the theory of evolution true – again, nothing could. The project’s findings are explained, ie follow from, the theory of evolution. According to Popper, there can be no positive/supportive evidence of a theory.

Popper thought the theory of evolution was tautologically true and considered it more of a philosophical research program. He (mistakenly) considered it unfalsifiable and concluded it wasn’t scientific. (Falsifiability was his criterion of demarcation between science and non-science.) Decades later, physicist David Deutsch corrected Popper’s mistake. The theory of evolution does make testable predictions: it says that adaptations arise gradually and that most mutations are unfavorable. So if we ever observed an adaptation that did not have any precursors in parent organisms, or if some genes underwent only (or mostly) favorable mutations, that would refute the theory of evolution. (See Deutsch’s book The Beginning of Infinity (BoI), chapter 4.)

I don’t know much about Young Earth Creationism, but from what you describe, it predicts (well, retrodicts) that the Earth is only 6,000 years old. And yet refutations of this retrodiction don’t typically (you are a glowing exception) persuade Young Earth Creationists that they’re wrong. That’s because the retrodiction is arbitrary and cannot be distinguished from the claim that Earth is 7,000 years old, say (compare BoI ch. 1, where Deutsch attributes progress to the rejection of the arbitrary).

That’s really one of the core differences between the theory of evolution vs something like YEC. Neither can be proven true, and both make testable predictions, but the theory of evolution has a rational character in that it is open to revision. If its predictions don’t match reality, its advocates have no way to evade the problem or continue their advocacy without making the requisite revisions. YEC, on the other hand, resists revisions because it’s arbitrary to begin with, among other reasons.

I believe the theory of evolution is true, or at least contains a lot of truth. But I also think there are gaps in our knowledge about evolution. For example, as Deutsch points out, we don’t really understand how to simulate it on a computer yet (even though many people think we do so routinely). I’d add that we don’t understand the origin of life to the degree that we could reproduce it on command in a lab (which would come with its own challenges). If we had really mastered the theory of evolution, we wouldn’t have any problem doing either one.