Before Facebook (and keyboard warriors)

This theory sounds plausible, until we take into account historical and archaeological evidence. Contrary to what most people think (and yes, that includes distinguished scientists too), for 99% of human history humans lived pretty much at peace with one another.

Before the Neolithic Revolution — that is, the wide-scale transition of many human cultures from a lifestyle of hunting and gathering to one of agriculture and settlement that took place some 12,000 years ago.