The Population Mystery

If a species that cannot provide for itself must decline, what does the following chart say about the ability of humans to provide for themselves?


Estimates for -400 through 1800 are from U.S. Census Bureau, "Historical Estimates of World Population"; estimate for 2000 is from U.S. Census Bureau, "Total Midyear Population for the World: 1950-2050." Year 1 is plotted as Year 0 for ease of illustration. "Upper" estimates are used for -400 through 1800 (where given) because those estimates are taken from a series that extends from -10000 through 1950, and the upper estimate for 1950 in that series agrees with the estimate for 1950 in the series for 1950-2050.