To think greed is some innate human trait seems to not be greatly substantiated by evidence on early human behavior. To see what we call greed all around us in market economy is only proof how we're all drilled from early childhood onwards to exhibit this behavior of greed, in accumulating money to survive, to archieve social status and approval etc. Drastic changes the economic system, and the very behavior set we are all programmed into, would more than likely regulate the behavior of greed. Though obviously that is extremely unlikely to happen.