Q: at what point in World History was the Earth's population half of what it is today? 1400? 1700? 1800?
A: 1963. Yes, the world in which I learned to walk, talk, appreciate Ruff and Ready, watch Lee Harvey Oswald get shot on live TV, and prepare for my Bar Mitzvah had less than half the number of people it does today, and it's expected to double again before you know it.
Maybe that's one of the reasons why the world economic condition is deemed more a security threat to the world than the 'GWOT'.
This issue dwarfs all others. Too many people and not enough Earths to go around, when everyone expects a 50 inch television, not to mention something to eat every day (with a glass of water).