Okay, setting aside that "human nature" is a naturalism fallacy, any appeal to "human nature" has to hold true for the bulk of human history, for as long as a human can be considered "
biologically modern", which is as "natural" as you can get.
So, if greed is a problem today, why was it not a fatal problem for our ancestors, say, 100,000 years ago? Surely hunter-gatherer societies are more "natural" than modern day urban ones.
See, the problem with the "human nature" arguement is simply this. Its arguers seem to think that "human nature" was invented 100 years ago or 2000 years ago and not 350,000 years ago, unless you think a time frame of 2000 years is enough for genetic shift to change "human nature" from a cooperative, social animal to a competitive, individual one.