Kluge a decent book with some interesting points, but overall I didn't think it offered any ground-breaking insights and was not particularly rigorously supported. I don't deny Marcus' main premise, that the brain is an imperfect kluge pieced together by natural selection and many of the traits we have do not promote happiness and wellbeing. But I think he underestimates the adaptive value (at least in a Darwinian sense) of some of the aspects of our brains. It's easy to overlook some subtle advantage of a trait and conclude it has no adaptive value. Gerd Gigerenzer's Gut Feelings: The Intelligence of the Unconscious, for instance, convincingly argues that many apparent reasoning errors are actually "highly intelligent social judgments" which are helpful overall in the real world (as opposed to a contrived logic puzzle, for instance).



It's easy to propose an alternative design for some aspect of the human mind without any real way to test if humans would indeed be better off with it. For instance, Marcus says "in a system that was superlatively well engineered, belief and the process of drawing inferences (which soon become new beliefs) would be separate, with an iron wall between them." But it's not clear to me that this is the best system. Each time we see a bird flying, should we conclude gravity doesn't exist since we're drawing inferences without regard for pre-existing beliefs? Sometimes observations seem to contradict well-founded beliefs and resistance to changing those beliefs is not necessarily irrational or counterproductive (although sometimes it is). Are we better off in the end with some other system? Perhaps, but would our ancestors have been better off with that system in the Pleistocene? It's not as simple a question as Marcus makes it out to be.



The original hardcover version of this book did not include the word "evolution" in the subtitle, and its after-the-fact addition to the paperback reflects the paucity of evolutionary information within. Marcus never really highlighted the crucial fact that our brains are adapted to the ancestral environment in which we evolved, which was in small bands of hunter/gatherers. Many aspects that are poorly designed for the modern world (our endless predilection for salty and fatty foods, for instance) may have been well adapted to life in the Pleistocene (where fat stores could be called upon during periodic food shortages). The same is true for all the hours we spend watching TV (perhaps a substitute for storytelling) or seeking non-procreative sex (sex and procreation, for the most part, could not be decoupled in the Pleistocene). While it remains true that these things are non-adaptive today (from a gene's point of view), it would have been enlightening to know that they were recently adaptive and not just evolutionary shortcomings, as Marcus suggests. He doesn't seem to be an expert on evolution; he mainly relies upon what he sees as imperfections of the modern mind in the modern world without much regard for the evolutionary history of those traits, and is quick to label them as evidence of a sloppy design.



For instance, Marcus cites a study which concludes "teenagers may have an adult capacity to appreciate short-term gain, but only a child's capacity to recognize long-term risk" and concludes "evolutionary inertia takes precedence over sensible design." But isn't it possible that post-pubertal peer acceptance is a critical factor for reproductive success, and therefore reckless susceptibility to peer pressure during teenage years is an adaptation and not just some evolutionary mistake? Studies show that teens actually overestimate the dangers of the activities they partake in, yet they do them anyway to gain peer acceptance. And it plausibly increases their reproductive success to this day, despite contraception.



To be fair, many of the traits described were just as maladaptive in the Pleistocene as they are today and many points remain valid.



For great discussions of mental imperfections, I recommend How We Know What Isn't So: The Fallibility of Human Reason in Everyday Life and Mistakes Were Made (But Not by Me): Why We Justify Foolish Beliefs, Bad Decisions, and Hurtful Acts). For a scientifically rigorous (and fairly technical) discussion of the evolutionary history of human mind, I recommend Melvin Konner's The Tangled Wing: Biological Constraints on the Human Spirit. Kluge also offers a brief and simplistic explanation of religion; for an account of the evolutionary origins of religion, I recommend Pascal Boyer's Religion Explained, or for a more technical and scholarly coverage of that subject, Scott Atran's In Gods We Trust: The Evolutionary Landscape of Religion (Evolution and Cognition Series).