The documentary Cave of Forgotten Dreams[2] presents the cave in a breathtaking detail, definitely worth a watch.
They must have been members of what David Deutsch calls a "static society". These are societies which actively try to keep things the same, and stamp out any innovation or differences. Things change there so slowly that the change is not noticeable within a single generation. In a 2011 interview with Ken Rose (https://groups.google.com/d/msg/beginning-of-infinity/dr64n4...), Deutsch said that "progress, from the point of view of the human species as a whole, is very recent and very rare. Through most of human history, people would live their entire lives without ever encountering an innovation, whereas now, we take it for granted that iPhone updates come more often than is comfortable."
For more, see his superb book The Beginning of Infinity (2010).