Few think Western civilization is on the brink of collapse — but it's also doubtful the Romans and Mesopotamians saw their own demise coming either.

If we're to avoid their fate, we'll need policies to reduce economic inequality and preserve natural resources, according to a NASA-funded study that looked at the collapses of previous societies.

"Two important features seem to appear across societies that have collapsed," reads the study. "The stretching of resources due to the strain placed on the ecological carrying capacity and the economic stratification of society into Elites and Masses."

In unequal societies, researchers said, "collapse is difficult to avoid.... Elites grow and consume too much, resulting in a famine among Commoners that eventually causes the collapse of society."

As limited resources plague the working class, the wealthy, insulated from the problem, "continue consuming unequally" and exacerbate the issue, the study said.

Meanwhile, resources continue to be used up, even by the technologies designed to preserve them. For instance, "an increase in vehicle fuel efficiency technology tends to enable increased per capita vehicle miles driven, heavier cars, and higher average speeds, which then negate the gains from the increased fuel-efficiency," the study said.