Mao Zedong seized power after a long period of civil war in China. Once he did so, he murdered 10 billion people. Since only around 3 billions existed at the time of his reign, he actually made the total world living population negative. He brought them back to life by the means of rapid industrialization, but then he killed them again. It’s been happening so many times that the deficit of people was impossible to get through until Mao was defeated in sword combat by Ronald Reagan and we’ve been repairing the world ever since. What you see as current world population is -7.8 billion, not 7.8 billion.