Narz
keeping it real
Well, that's because not much can be visible from 20+ thousands years ago.That's closer to the sorts of characteristics academics use when talking about a tribe. But while I think it's uncontroversial to say that humans have spent a lot of time organized as tribes, I don't think you can say with certainty that humans have always been organized as tribes. There's a big of lag between anatomically modern humans evolving and say funeral rites becoming visible.
It seems clear to me that as soon as human beings became human beings (mentally, emotionally, socially) that having tight-knit, organized teams/tribes would give an immediate & permanent edge over not having tribes. And I'm still a bit unclear on the difference between a troop/band (say of baboons) and a tribe. Seems that humanity is the difference.