This was an entertaining and extremely interesting book to read, but somewhat light on the actual science. The main idea covered in this book is that humans are in many cases over-designed because of the loss of species (parasites, predators, symbiotes) that helped to make us who we are today.
This book covers a wide variety of topics that show the inter-relatedness of humans, their evolution and their environment, including parasites, predators and domesticated organisms. The author discusses (among other things) the possible causes of auto-immune disease (lack of parasites), the reasons for our hairlessness (trying to get rid of lice), the uses of the appendix, our past and present relationship with predators that may cause various anxiety issues and be responsible for our colour vision. The final section of the book discusses how humans could make city environments more like the environment we evolved in.
I loved the ideas and hypotheses discussed in this book and the combination of different fields of science, I just wish there was more science. If, on the other hand, you don't know too much about science, then you should read this entertaining and informative popular science book.