Ah, good ol' "human nature." Marxism, and all the fields of study it has spawned over the past 150 years, and all the intellectual work and research, just happened to ignore “human nature.” It is amazing how this is presented as an intellectual critique, and the Marxist dialectic presented as anti-intellectual, when the human nature counterargument is based on the assumption that human motivation is monolithic, simplistic, and in no way influenced by external or personal factors that differ from place to place, person to person, era to era. It is intellectual laziness at its finest, because it relies on no research, or even personal observation beyond the behavior of a few extremely wealthy individuals.

The idea that human nature is greedy and selfish and that these are thus primary motivating factors that are ingrained in the way we behave has been debunked by studies performed by the University College of London, M.I.T., the University of Amsterdam, the University of Princeton, the University of Berkley, Washington State University, Emory and Carnegie Mellon [1] [2] [3] [4] [5]. They're artificial, and exist as a by-product of our survival instinct. Under our current economic system, as well as its previous two exploitative iterations (feudalism and slavery), money equals survival. The more you have, the better your chances are.

This is supported by the works of evolutionary biologist John Maynard Smith, anthropologist Robert Trivers, political scientist Robert Axlerod and Primatologist Frans De Waal, and economist/zoologist/evolutionary theorist Peter Kropotkin.

All of these go into detail into why human beings are much more cooperative, altruistic, reciprocal, mutualistic and empathetic with one another than they are selfish, greedy or egocentric. None deny that these latter aspects of behavior exist, but simply hold that they do not account for the concepts of emotional contagion, targeted helping, cultural transmission, consolation, game theory or self-recognition. If you can explain these with 'human nature is selfish and greedy', by all means I'd love to learn how.

Source #2, particularly, which is Dan Pink's seminar on Mastery, Autonomy and Purpose, reveals that once people earn enough money to satisfy their basic needs they become motivated by having a sense of autonomy (ie. the desire to be self-directed), mastery (ie. the urge to get better at things), and purpose in their work and life. Money is simply a means to those basic needs, and if you were to eliminate it altogether, and provide those means to the people another way, or for those means to be guaranteed/readily and freely available to them, people would no longer engage in the kind of behaviour you call "greed".

The need for food, water or shelter is biological -- a lack results in death. However, human society has changed how and why resources are gathered. The biological necessity is the same: humans need to eat, drink, sleep, stay out of the rain. But society has developed a way to transport current resources into the future for use in that future -- money. Thus, humans seek money.