Some milestones, like obtaining a driver's license or getting called hipster trash in Internet blog comments, are worthy of celebration. Others, like the Earth's carbon dioxide levels reaching their highest monthly average concentration in human history, are not so great. And unluckily for us—"us," as in all of the planet's living beings—we reached that particular milestone in March, according to scientists.

In March 2015, the planet's average carbon dioxide levels surpassed 400 parts per million for all 31 days. Chillingly, scientists say CO2 levels haven't been this high in 4.5 million years, or perhaps even 15 million years, with a research team once finding those levels ranging from 365 to 415 ppm during that period. Note that humans have only been around for about 2.5 million years, and the last time the Earth's CO2 levels were like this, the planet was run by great apes. GREAT APES. The only thing worse than destroying our breathable air is proving even a fictional Charlton Heston right.

Carbon dioxide levels have been rising since the Industrial Revolution, when they hovered at 280 ppm. The current record amount is expected to drop a bit by next month, but scientists say there's no question that greenhouse gases are causing CO2 levels to rise nearly permanently. We can expect 400 ppm, which we reached for the first time ever in April 2014, to be the new normal by next year: "Elimination of about 80% of fossil fuel emissions would essentially stop the rise in carbon dioxide in the atmosphere, but concentrations of carbon dioxide would not start decreasing until even further reductions are made and then it would only do so slowly," James Butler, director of NOAA's Global Monitoring Division, said in a press release.

Of course, a slow CO2 level reduction is better than no level reduction at all, and our global leaders could make an effort to alleviate the climate change crisis for future generations. But why bother?