[Exenith]

Some rudimentary consideration of what life is like in a tribe would suggest that greediness and hoarding are evolutionary weaknesses. If you take too much for yourself, others in the tribe get pissed off and get rid of you. If you have a tendency to hoard things, you're going to have a hard time managing a nomadic lifestyle that necessitates light enough loads to carry. Not to mention -- things rot, things break, things get lost, and if you've just used up all the natural resources around you, you're screwing yourself quite hard.