Undercutting Defeater?

Scott Adams who draws the Dilbert cartoons said several things on his blog in the wake of the Trump election that I thought were interesting. His main point was that the aspersions being cast on Trump voters by those who voted for Hillary make little sense, which was itself an interesting argument, but not what I want to talk about in this post. What I want to think about here are these sentences:

Humans did not evolve with the capability to understand their reality because it was not important to survival. Any illusion that keeps us alive long enough to procreate is good enough.

This is a revealing assertion for two reasons. It's a view widely held by Darwinian thinkers and, if it's true, it casts grave doubt on the rationality of belief in evolution. It actually undercuts that belief.

If Adams is correct then the vast majority of our beliefs about reality could be, for all we know, illusions which have become fixed in the human population because they promote the survival of the species. If this is so then we really can't trust any of them, especially our metaphysical beliefs, to be true. And, since our belief in evolution is one such belief, we have no grounds for believing it itself is true.

In other words, the belief that nature selects traits or beliefs that promote survival rather than truth undercuts belief in natural selection. It could well be just another of Adams' illusions.

I don't want to make too much of this because Adams, though a very bright guy, is a cartoonist and not a scientist or philosopher of science, so he doesn't speak with any special authority on matters in these fields. Even so, to the extent his words reflect a common assumption about Darwinism, they should give Darwinians pause.