I listened this morning to an interview with Dr Unwin, in which he was asked to provide an instance of an item of "evidence" whose probability he had systematically assessed.
The example was well chosen: evolutionary theories which seek to account for apparently irrational extremes of altruism.
I apologise if my response does not do justice to the arguments in the book, which I have not yet had the opportunity to read. I can only plead that it is at least based on his own explanation of a sample argument, rather than a review by a third party.
My problem? Dr Unwin lined up an explicit hypothesis, drawing a plausible causal relationship between evolution and behaviour, against a catch-all proposition, namely that everything which science cannot explain can be scored as one for God.
Surely it is misleading to provide such a "default cause"-- one which requires no evidence for a causal relationship, rather simply a spurious absence of alternatives to such a relationship, caused by having set up a false dichotomy in the first place?
To try and explain this another way, this approach collapses a virtually infinite range of alternative explanations, many of which might fall on the science side of the line, into evidence for the existence of God.
To instance a couple of alternative explanations (NB: These are hypotheses, not statements of fact):
1) Genes are pruned by evolution to discourage non-altruistic behaviour. A plausible mechanism would be the non-survival, to critical mass, of social groups which do not display altruism, in comparison or competition with groups which do. Excessive altruism would not be specifically selected against by evolution, unless it threatened survival. Instances of altruism to strangers are statistically rare and not typically survival-threatening, in the sense of survival of our genes. Even the ultimate (and vanishingly rare) example of self-sacrifice to save a stranger is only punished by evolution if we have not yet bred to capacity.
2) Individuals bear genes fashioned by evolution, but individual behaviour exhibits fluctuations from the exact circumstances which fashioned those genes. Nurture vs Nature, free will, etc etc.
3) Altruism could be evidence for religion, rather than for God. We know religion exists, but we are supposedly (in this discussion) keeping an open mind on God. In this context, the purpose of religion is to provide society with a coherent and persuasive set of guidelines for behaviour.
The fact that these guidelines sometimes work for "good" does not rely on the existence of God, just as the fact that they sometimes emphatically do NOT work for "good" (as in Ireland, Bosnia and the Middle East) does not disprove the existence of God, or altruism.
4) Why God? It seems equally plausible to postulate manipulation of our behaviour (in the direction of irrational altruism) by, say, a more sophisticated life-form from elsewhere. There is plenty of corroboration, in the form of UFO sightings. Should we believe these? No, but we do not, or should not, automatically believe individuals who claim to have witnessed God.
Admittedly there is a huge disproportion in numbers in favour of God vs little green men. I willingly concede that organised religions *have* been phenomenally successful, but success does not necessarily validate - witness Adolph Hitler, or daytime television.