Population growth is at the root of many serious environmental problems. From the ancient Babylonians thousands of years ago, to Thomas Malthus hundreds of years ago, to present day neo-Malthusians, humans have always seemed to possess an awareness of Earth's limitations in the face of growing populations. Today, our ability to accurately quantify, monitor, and control population growth is very sophisticated. We can measure growth and make predictions about world growth with mathematical and computer models. Can we prevent disaster? Despite dire predictions in the past, humans still inhabit Earth. Some economists would argue that this is because .