This is about as good as books get. Every observation and comment is backed up by evidence from scientific literature, ranging from the anthropological to the physiological. You get a book about running that also takes in a spectrum of other forms of exercise that allude to, contains, or border on that fundamental activity. Actually, I suspect, after reading this, that brisk walking is more fundamental, in the sense that it has a stronger basis in the evolution of human beings as hunter-gatherers. This is made abundantly clear in Exercised. Hunter-gatherers would have looked upon (indeed do look upon) unnecessary jogging as a ridiculous waste of calories.
If you are a Born-to-Runner, one who has read and internalised Chris McDougall's book about the Tarahumara, then there is a lot for you in this book, but don't expect your biases to be confirmed. As a rigorous scientist, everything Lieberman examines he does so with a sceptical and critical eye. He expects you to do so when reading this book, but I could not find fault with it. Lieberman is himself known as 'The Barefoot Professor' in running circles, indicating the extent to which he internalised the dogma around all things McDougallish. Though, of course, his own time in the field working with San, Hadza, Tarahumara, and other hunter-gatherer cultures are a more fundamental reason. He is critical of the Born to Run cult, and gives careful consideration and weight to running with shoes.
We don't get to running until around page 200, before which we are led systematically through myth-busting chapters on sleep (5-7 hours is ideal, and if you sleep more than 8 hours you are more likely to die young); rest (we were born to REST not RUN); laziness, for which we are also evolved, noting the amount of time our ape ancestors and our hunting-gathering fellow humans do actually spend resting (it is a LOT); sitting (slouching is just fine, and chairs are irrelevant); beds (we don't really need them); speed (humans are slow and ungainly runners, even Usain Bolt); strength (brawniness had its place in the past, but better is to be strong); aggression (humans are better at proactive than reactive violence); walking (you can lose weight by doing it BRISKLY; and 10,000 steps is a real figure in terms of health); running (it is basically a form of dancing, which is basically hopping from one leg to another over and over again), and many more myths busted.
After all the evidence, supported by clear and convincing graphs, has mounted throughout the book, we are given a tour of what happens when we age and don't exercise; versus a life lived actively. We note that many lazy people live long happy fulfilling lives; and that many exercists (his word for proselytising exercisers constantly urging us to exercise) don't. Lieberman takes these cases apart using both logic and evidence. The lazy longevity phenomenon is countered by pointing out that such people could have lived even longer better lives had they exercised; those marathoners who died young from heart attacks might have died earlier had they not been so active (I hadn't realised Jim Fixx and some of the others responsible for the running boom had led such nutritionally debauched lives before they became runners until I read this book).
The final chapter is a mini-book for the use of exercise as both tool and dosage for attacking a range of diseases from cardiovascular, to cancer, to mental health. Nowhere is exercise given as panacea, everywhere its role is precisely weighed up against other courses of action, and varying dosages and types, from cardio to weights (both of which are highly recommended, with the weight falling more to the former). 150 minutes of moderate to vigorous exercise per week is the basic prescription for all, in a nutshell, with two days of weights. He even gives a few pages discussion to running injury, and the running aspect will be quite satisfying to my readers who pursue this great endeavour. Reading this book will deepen both your love and sense of purpose around the importance of keeping on with the exercise, however much you can do, in whatever form, for a happier and healthier life.