Last time I checked, humanity was supposed to hit the seven billion mark next summer. But apparently that date’s been moved up. Now, it’s supposed to happen on Oct. 31. We passed six billion in 1999. So in roughly 12 years we’ve managed to add one billion people. By 2050, the linked article projects, we could reach 9.3 billion. And worst case scenario is that the population could hit 15 billion by 2100.