To my mind, there is more to this question than the one which framed the previous post - "Can evolutionists believe in God?" In thinking about this question, I am assuming by "God" that we are talking about the God of the Bible, who (if you accept what the Bible says about itself) makes himself known as creator, sovereign and redeemer of this universe.
In a sense, it is reasonable to say that "only a fool doesn't believe in evolution". Evolution happens all around us - organisms adapting to their environment through darwinian processes.
However, the fact that evolution takes place doesn't mean that it is reasonable to claim that darwinian evolution (random mutation, natural selection) has achieved what its proponents claim it achieved. Humans have known about selection, and "directed" evolution for millenia - we call it breeding. The finches on the Galapagos Islands that Darwin studied do develop over time, as changes in climate cause changes in the abundance of different foods for them. In actual fact, if they weren't able to adapt to a changing environment, they would not be well designed - they would likely not have survived as long as they have! But this doesn't prove that finches share a common ancestor with turtles. This observation may simply demonstrate that they were designed to adapt to changing environments. After all, a good human designer will allow their designs to adapt to such changes.
What has happened when evolution is considered is that a presupposition has come into play - the presupposition that there is no designer. The logic is something like this:
Premise: Variation takes place through darwinian processes (observation)
Premise: There is no designer (presupposition)
Conclusion: All life developed through darwinian processes
Note again that the second premise is not a matter of observation. Before the conclusion can be assumed to be true, the second premise has to be justified. Let us say that at least it continues to be a matter for debate.
And in that context, the evidence has fairly consistently proved to fail to support the presupposition. For example, it was assumed by materialists that the universe had always existed - and then it was discovered that the universe did have a "start point". (The name "Big Bang" was given derisively by Hoyle, who disliked the idea intensely from a philosophical point of view). It was assumed that life in its simplest forms would be ... well, simple. And then it was discovered that in actual fact, the simplest forms of life are still incredibly complex. It was assumed that the earth was a fairly insignificant, typical planet. And then it was discovered that the earth is incredibly finely adapted to the presence of complex, intelligent life ("Rare Earth", Ward/Brownlee). I could go on....
None of these facts invalidate a materialist perspective on the evolution of life. However, they do demonstrate that there is no good track record of collecting evidence to support the presumption that there is no designer.
Let's assume, for the moment, that the history of the universe is pretty much as the scientists have concluded - it is around 13.5 thousand million years old; the solar system is around 4.5 thousand million years old; life first appeared around 3.2 thousand million years ago; complex body plans appeared around 530 million years ago. In the context of the appearance of life, there are certain facts about the process which at least at the moment remain unexplained.
- biogenesis - the initial appearance of life - materialists often specifically exclude this issue from consideration when they talk about evolution. Ward and Brownlee ("Rare Earth") argue that it may be common - but the truth is nobody really knows how it happened, or how feasible it is;
- the organisation of eukaryotic cells - animal and plant cells are much larger, more complex and more diverse than bacterial cells, and again, there are only suggestions as to how this crucial evolutionary step took place;
- the organisation of cells into multicellular organisms - this requires differentiation, structure and genetic switching, none of which has the same level of significance in single-celled organisms;
- the Cambrian explosion - the sudden (in geological terms) appearance of almost all modern phyla about 530 million years ago, with little in the way of apparent antecedents;
- the development of complex biochemical systems - whilst the concept of "irreducible complexity" may be disputed, it is certainly the case that systems like flagella, blood clotting, vision and so on are highly intricate, and would tax the ingenuity of human designers. I am sceptical that a "blind watchmaker" would be capable of producing such systems;
- evolutionary transitions between phyla - bear in mind that for the most part even changing the number of chromosomes in an animal can have a drastic effect on its ability to survive: this has to happen over and over again as biodiversity increases;
- the radically different nature of humans, and the consequent achievements of their sapience.
It would be a logical mistake to argue from this that there must be a designer, I think. That would kind of represent a "God of the Gaps" type argument - as the gaps are whittled away by naturalistic explanations regardless of how improbable they are, the materialist would then argue that he or she has done away with the need for God. It would also be a mistake to assume that we might be able to identify a kind of "miracle" taking place at each of these stages - or, for that matter, that if we can identify a possible naturalistic explanation, that "proves" that there is no God.
Instead, think of what we now know about the development of life. Is it unreasonable to believe that there is no sovereign intelligence that has directed this process? Isn't it more unreasonable to believe that all of this should have happened by chance, in a universe that is in fact completely indifferent to human existence?
So I am strongly convinced that, even if a person believes in evolution, this does not mean that they have grounds for discarding belief in God - that belief is neither foolish nor misguided.