I felt like large portions of this book were based on a few misunderstandings on the part of Hahn and Wiker. For instance, the authors wrote page after page explaining how exceedingly unlikely it is that a modern living cell could randomly jostle into place and come to life. Dawkins would agree with them on this point; even the simplest modern cells are extremely complex. But in The Blind Watchmaker (a book cited repeatedly by Hahn and Wiker in Answering the New Atheism) Dawkins devoted an entire chapter to the subject of the origins of life. Dawkins even wrote "the only machinery of replication that we know [DNA] seems too complicated to have come into existence by means of anything less than many generations of cumulative selection" [p. 200]. He went on to explain how simple pre-DNA replicators could have provided the scaffolding necessary to evolve modern DNA replication. Hahn and Wiker quoted Dawkins from this very same chapter but omitted his explanation of the origins of life and instead erected a straw man argument to knock down. It's hard to believe that they were unaware of Dawkins' explanation, especially seeing as how Dawkins also devoted another chapter on the origins of life in Climbing Mount Improbable, another book cited repeatedly by Hahn and Wiker. From Climbing Mount Improbable: "the original replicator probably was not DNA...unlike DNA, the original replicating molecules cannot have relied upon complicated machinery to duplicate them" [p. 285]. The (intentional?) omission of these arguments was disappointing.
The authors explicitly do not deny "that evolution is in very important ways a partial cause of human intelligence" [p 82]. However, they argue, there is "an enormous discrepancy between what is needed to survive, and the intellectual ability we've actually got" [p 50]. Human brains can figure out "what's going on inside atoms or inside black holes" which is "not at all necessary for Darwinian survival" [p. 50]. But various theories explain humans' intellectual capacities: for example, the use of language provided a significant benefit for those best able to use it, which led to more capable brains, which led to more complex language, which fueled a rapid self-sustaining upward spiral in mental capacity and language complexity. And there is no shortage of examples of evolved traits later being put to uses far different than those that provided the original benefits. There is little mystery here. Plus, human minds have great difficulty understanding and imagining quantum mechanics, for instance, because the concepts are very different than the familiar ones that we need to survive. This makes perfect sense in light of evolution.
Dawkins' main argument in The God Delusion is that "a designer God cannot be used to explain organized complexity because any God capable of designing anything would have to be complex enough to demand the same kind of explanation in his own right" [p. 136]. Hahn and Wiker assert that "it is only in Dawkins' treating God as having an evolved, material intelligence that allowed him the dubious luxury of discounting His existence as very, very improbable...since God is by definition purely spiritual, then the contingency of material atom-shuffling is inapplicable" [p. 65]. But if not atom-shuffling, then what? However God came to be still needs an explanation which is entirely side-stepped by the authors. Why would non-physical intelligence need any less explanation than physical intelligence? I can understand it would be a different kind of explanation, but the authors offer none at all and utterly fail to counter Dawkins' main argument. It's like answering "why is the sky blue?" with "it's not blue, it's light blue" and then failing to offer an explanation of why the sky is light blue.
Most of the authors' discussion of atheist morality is based on a simple assumption that is just false: that whatever is best for our selfish genes is by definition "moral". "Does it promote survival? If it does, it is `good'" [p. 118]. Thus, they question how Dawkins can condemn the brutal practices in the Old Testament as immoral since natural selection is equally brutal. Even granting their premise for the moment, they do not make any attempt to defend the atrocities described in the Old Testament as moral according to their own God-given standard of morality. They criticize morality based on natural selection as no better than that of the Old Testament, then go on to upbraid morality based on natural selection as repugnant. Does that mean the morality taught in the Old Testament is also repugnant? Because that was what Dawkins argued and all the authors effectively responded with was "oh yeah? Well your morality is repugnant, too!" But in doing so they assumed that what is good for our selfish genes is by definition "moral" according to the atheist. This leads to all kinds of wild conclusions that sound more like a caricature of imaginary outrageous "evil people" rather than real life atheists. Dawkins explicitly states in The Selfish Gene "I am not advocating a morality based on evolution" [p. 2].
Either Dawkins is right and there is no personal God, or he is wrong and there is one. If he is right, then all the moral principles of Christianity espoused by the authors must come from the very same sources as Dawkins' morality.
UPDATE:
Since writing this review, I've read a few books about the evolutionary origins of morality. I recommend
The Origins of Virtue: Human Instincts and the Evolution of Cooperation. The theory goes like this:
Our ancestors who were genetically predisposed to cooperate with each other were more likely to survive and pass on their genes than their selfish counterparts, presumably due to the efficiencies and advantages of teamwork. Similarly, our ancestors who refused to tolerate social injustice perpetuated by others were able to avoid being cheated and passed on the genes that built their judgmental brains. Those who felt guilty for committing actions that ruined cooperation were less likely to take those actions and were more likely to cooperate and pass on their genes. We are their descendants. We are no more free to decide not to feel guilty for betraying a friend than we are free to decide not to feel pain from slamming our hand in a car door. The emotion of guilt, like the feeling of physical pain, is an involuntary reaction that has a powerful influence on our behavior. And we all feel it, whether we believe in God or not, because we all share the genes that make the type of brains that act that way.
The final chapter is a truly ridiculous "warning" to all the faithful of the awful perversions of society that would surely befall any country who allowed an atheist any kind of political power. It is reminiscent of the ludicrous 1930's anti-marijuana propaganda film "Reefer Madness" which depicted mild mannered citizens transforming into raving lunatics, killing each other and jumping out of windows after smoking marijuana. The atheists will take your children away! They'll shut down the churches! They'll mandate abortions and euthanasia! The authors described Hitler, not Dawkins, and not atheists in general.
It would take another entire book to counter all the authors' arguments, so I have offered only a few here. But despite this books shortfalls, it is an interesting read which provides insights into Catholic philosophy and views of atheists.