“Leave enough for everyone.” That’s what my mother used to tell us at dinner. However, the holiday season reminds me that human nature is far from innately moderate in consumption. With Black Friday as a kickoff, consumers will spend more than $600 billion by Christmas in the United States alone. As I witness droves of shoppers running through malls and stores, I wonder if their desire is driven by some insatiable appetite for their favorite products or something more fundamental about human nature.