Lieberman presents an interesting argument about how human brain is wired to be social, it is a matter of survival as well as a great advantage that differentiate man and other beings in the animal kingdom.
I find the evidence (experiments) in the book rather fascinating, especially the finding that the brain region related to making sense of social world is turned on active automatically from time to time. I didn't realize that getting into others' mind is such a great achievement, it is taken so much for granted. Some efforts to explain autism and Asperger related are interesting too. Other experiments about how the brain perceive physical pain and mental pain might be of interest to some readers, too, though it is not surprising as we have come to accept that, say, depression can be treated/alleviated by medication. The rest aren't exactly new.
What I am uncomfortable with, however, is the stretch of conclusion that the author likes to make. The evidence that he presents does prove the importance of the social function that revolution has accumulated for human, how it intervenes with other functions, but it does not tell a cohesive and complete picture yet about how people deal (consciously and unconsciously) with social life itself. Yet he, quite a romantic scientist, attempts to give advice exactly on the latter, suggesting several changes in the education system, the work environment, and advice on how we lead our life. The crux is (a good idea) to take care of your social needs, but the method, by being more sociable - that, I was uncomfortable with, being an introvert myself (and content with that).
So many things are incomplete. People tend to conform to society, yes. People's sets of beliefs are often unconsciously formed by the environment that they live in, yes, that's true too. The way Lieberman writes makes it seem that men are generally helpless against the the brain and its wish to be harmonious with other members of the society. On the larger scale, how would one explain revolution, the emergence and spread of new and radical ideas, the opposite of conformation? And then, on a smaller scale, how would one explain the calmness of a mature person who, of course, still cares about how some others feel, but just some loved ones and not the whole abstract society? That's still a happy life, no doubt. There are smaller and still meaningful ways to lead a happier life. Being well informed enough, we can do something about it, accept the limit but also push the boundary a little bit and see how it goes.
I never have this type of criticism with Kahneman's book, since Kahneman focuses primarily on the scientific findings and only makes some careful and practical suggestion on how we deal with and accept the limitation of our brain: little habits to change/form to boost performance, to deal with nervousness, depression, to make better decision, that kind of thing. This one, however, strives too much to be profound. It gathers scattered findings and tries to weave a story out of it, but honestly, it doesn't work like that. Usually one starts with a question and studies all aspects of it in depth, minimizing the gaps in logic, or if there are, admit and be aware of them.