I'm no anthropologist but may be able to help you with your second part, what do you mean by 'true civilisation'?

This is a difficult question to answer because of the ambiguity of the word "civilization", but:

In anthropology, a tribe is the word generally used to refer to a group of people with a limited amount of social hierarchy - not totally egalitarian like bands, but less hierarchical and socially complex than larger chiefdoms or civilizations. It's difficult to pinpoint the first tribes, because this would have taken place long before any system of writing, potentially tens of thousands of years ago. What was crucial to the development of civilization was the development of agriculture during the Neolithic revolution - the first reason to stay put for a long time.