Currently, the first evidence of Homo Sapiens, man able to think, giving credence to his existence is about 100,000 years ago.  This evidence is in the form of weapons, tools, habitats and devices used to live.  As the numbers grew, the primary and constantly pressing need was for food.  Some members who found themselves in fertile areas (e.g. The Indus Valley) learned how to grow food and feed their animals without constant nomadic movement to acquire sustenance.  
Refinement of this bedrock ability to grow food broke his shackles to foraging and allowed him to stay and build in one place.  Not having to move-on, enable individual man to coalesce into groups, and groups into tribes.  We shall see that tribes for many centuries would be the primary form of man’s socialization, usually with groups possessing similar goals, traits, values, religion and purposes.  What is often overlooked by the casual reader of ancient history is that the formation of tribes was occurring across the world, but at differing rates of sophistication and maturation which, in turn, would be a source of almost indescribable suffering, destruction, carnage and death as well as surprising growth, discovery and achievement.