I quite liked "Sapiens". Like most folks, I always assume (wrongly) that evolution runs forward in a positive direction. "Sapiens" shows that the actuality is really more mixed than that.
Harari points out some other details that I hadn't considered. Hunter-gatherers did not spend all of their time hunting and gathering - they likely spent fewer hours per week in those activities than current homo sapiens spend in their worklife. Thus, our ancestors probably had very active social lives, and the social aspects prove to be the most important parts of our dominance.
Homo Sapiens may prove to be a larger "extinctionator" that even the largest asteroid, particularly with respect to large land mammals, which we seem to hunt to extinction on every continent soon after we arrive on the scent.
I kind of knew theories of the origins of myth and religion, but hadn't realized their power to unite larger groups of people than more direct social interactions allow. Harari explains that social groups begin to fall apart when you get to the 100's. I tend to think about a primary school, where there may be a few hundred students, and the K-3 or 6-8 grade levels form a sort of community and know each other, but when you get to a large high school, the groups are broken down more, as the grades are too large for all students to know each other. Harari attributes the power of myths and legends to allow strangers to align even without personal connections (e.g. cultures, tribes, religious factions) all of which allow Sapiens to combine in large enough groups to overcome hurdles that would knock down the largest of pre-existing species, who would operate as smaller family groups or extended herds (elephants, for example).
I had not considered the pros and cons of moving from hunter-gatherer to farming in any particular detail. Planting caused some learning to be rewarded (e.g. tracking seasons, learning how to plant effectively) but along with the loss of mobility came the need to create permanent shelter, which, in turn, lead to defense of land and possessions, which could now be kept and stored. This also led to organization of people to defend land from wondering troops of hunter/gatherers or other species of man or animal that would threaten the now "owned" land. Further, I had assumed that the trade-off was universally positive - farming was inevitable growth of the species (and in terms of # of bodies, it was), but didn't recognize that the reliance on singular crops cost a lot in terms of physical health and was susceptible to drought or plague in ways that hunting and gathering was less susceptible to. However, staying in place allowed for large families, which were needed to farm, an allowed enough bodies to be born to handle very excessive mortality (e.g 1/3 or 1/2 of children dying young). These large families also proved to swing the balance toward continued farming as farmers with extended family groups would always outnumber roving hunter-gatherers, which reduced the land for gathering, and the #'s favoured farmers in any battles that might occur.
Each of the four revolutions of humankind (Cognitive, Agricultural, Unificaiton, Scientific) is explained simply, clearly and with insight to make the transitions' importance visible and clear.
