Join host John Green to learn about human population. How many people can reasonably live on the Earth? In 1800, the human population of the Earth passed one billion. Thomas Malthus posited that growth had hit its ceiling and that the population would level off. He was completely wrong, as there are currently seven billion people on the planet! John will teach a little about how Malthus made his calculations and explain how Malthus came up with the wrong answer.