"Dawn of civilization"?

In my World History class, we were speaking about this, the so-called "dawn of civilization". Now, it's taught as fact in that class (and I also remember this from high school), that the dawn of civilization began roughly 12,000 years ago. 12,000 years... Now on top of this, it appeared to be happening within the same few thousand years all around the world in groups that had been disconnected from each other. This was a question in this second class on world history. Why development now? What could cause these disconnected groups around the world to take off exponentially all of a sudden? There were several hypotheses given, but to me none of them made any sense at all. The "oasis" hypothesis which states that people gather near water; the "social" hypothesis which states, more or less, that people are social (duh?); and a couple other hypotheses that basically explain why one group might begin to develop. But why in the same period of time did human beings begin to develop? There is no explanation for it as I can tell, not without incorporating concepts from other areas of study.

First of all, a history major needs to really look at the question here. We're talking about in a few thousand year window that separate groups began to develop... the question is not why one group might develop, but why several groups might develop at the same time although seemingly disconnected. We're talking about bipeds who have arguably been around for at least six million years. Six million. That is a big number. So why then, after six million years of animal life, did bipeds make the jump globally to develop in a different way? To me, it's a mystery, although I see no reason to assume that just because we don't have records of civilization earlier than 12,000 years ago means that none existed earlier than that. I see no reason to omit the possibility that entire civilizations could have been wiped out many thousands or millions of years ago in natural disasters, leaving virtually no record.

I suppose this is the original purpose of such studies, to dive into the unknown and to look into possible reasons for what we do know. But I find that many times in the educational system the line is forgotten. Teachers tend to state theories as facts, and then their students become teachers and do the same thing. The line is lost between theory and fact, and in my world it is imperative to differentiate the two.

In my first math class, the teacher was explaining that testing this certain equation, the solution seemed beyond all shadow of a doubt to be a certain number. But, in math, 'seems' is not good enough. An answer must be definite to be an answer. And so, to me, it remains an interesting uniqueness about math, that it deals with definite truths, and when it doesn't it makes clear the line between theory and fact.