When I wrote "Life fascinates us because of its adaptive complexity," I meant "life" in the biologist's sense of "plants and animals," not the broader sense of "our existence." Life in the broad sense, of course, is fascinating for many reasons.
I am puzzled by your question of why I did not "admit," "with conviction," that evolutionary biology and neural computation "cannot explain" major human activities. It's like admitting that some events defy physical laws, or that some metabolic processes cannot be explained as chemical reactions. Certain theories are so deeply entrenched in our understanding of the world that when we face an apparent anomaly, our responsibility is to come up with testable explanations. Throwing up one's hands and saying that no explanation is possible just guarantees that one will never understand the anomaly. Of course, if no hypotheses are available, or if all are falsified, one rejects the theory, but only by trying out hypotheses can one can get to that point.
Evolution and neural computation are well-entrenched theories, so if a phenomenon appears to be inexplicable by them, it's important to see whether the discrepancy is fundamental or temporary. In the case of sentience, free will, and moral truth, I argue that the discrepancy is fundamental. But that is a radical conclusion, and most of my fellow scientists reject it.
The case of art, music, narrative, humor, and religion--specifically, how they arose out of a brain designed for survival and reproduction--is different. I think our puzzlement comes from a failure of our scientific imagination; there are many possible explanations, and we have only begun to consider them. Of course I don't have definitive answers, but I don't claim to--my goal was to convert the questions from anti-Darwin ammunition or head-spinning mysteries into tractable research problems. The chapter reviews extensive literature on these topics and proposes new hypotheses; it has already attracted interest from scholars in music, anthropology, and narrative.
Incidentally, there is no contradiction between saying that religion and music have no adaptive function and trying to explain them in Darwinian terms. If they have no function, but are complex, they must be byproducts or spandrels of something else that does have (or did have) a function. We still have to identify the something else. The arts, humor, and religion are products of human minds, and surely bear the stamp of our visual and auditory systems, our intuitive psychology, and our social emotions.
Politics and history, too, ultimately connect with an understanding of human nature. You attribute social progress to people rebelling against their oppressors and to the fact that what seemed morally acceptable in one age cannot be tolerated in another. I agree. But why do oppressors sometimes crumble in the face of rebellions they are capable of crushing? What makes people suddenly change their convictions about what is tolerable or intolerable? Perhaps you're not curious, but I am. More to the point, the discussion comes at the end of a chapter that argues that human nature is not innately enlightened or indiscriminately kind. So the questions are real challenges and cannot be ignored.
Perhaps my proposals are wrong, but we'll only find out by considering them, or proposals like them. What are the alternatives? If the brain is not an information processor, what makes it smart--an immaterial soul? If the complex organization of the brain did not come from evolutionary forces, where did it come from--Lamarckian evolution? Divine creation? "Culture" is not an alternative, because the capacity for acquiring and contributing to culture is itself a set of psychological mechanisms that needs an explanation.