Prior to the Industrial Revolution, human society was sustainable by default. Human activities were at small scale compared with the immensity of the Earth, so that whatever humankind did, the stability of the global ecosystem was not put at risk. Communities could collapse as certain cultures and behaviours were found to be flawed. Whole civilizations could disintegrate, consumed by corruption, complacency or any number of failings that afflict human societies. There would always be another tribe to take up the running for humanity to continue.