What if there were a solution to many of the global problems that confront us, from climate change to poverty to civil wars? There is, but it is starved of resources. It’s called family planning, and it has been a victim of America’s religious wars.

Partly for that reason, the world’s population just raced past the seven billion mark this week, at least according to the fuzzy calculations of United Nations demographers. It took humans hundreds of thousands of years, until the year 1804, to reach the first billion. It took another 123 years to reach two billion, in 1927. Since then, we’ve been passing these milestones like billboards along a highway. The latest billion took just a dozen years.

In 1999, the United Nations’ best projection was that the world wouldn’t pass seven billion until 2013, but we reached it two years early. Likewise, in 1999, the U.N. estimated that the world population in 2050 would be 8.9 billion, but now it projects 9.3 billion.

What’s the impact of overpopulation? One is that youth bulges in rapidly growing countries like Afghanistan and Yemen makes them more prone to conflict and terrorism. Booming populations also contribute to global poverty and make it impossible to protect virgin forests or fend off climate change. Some studies have suggested that a simple way to reduce carbon emissions in the year 2100 is to curb population growth today.