Monster from the Past

By Michael D. Lemonick

Jonathan Bloch was thrilled with the haul of fossils he’d begun unearthing in Colombia starting about five years ago. The lush landscapes of northern South America aren’t generally the most rewarding places for paleontologists like Bloch. “They’re covered with forest. You can’t see the rocks.” But a colleague had told him about a vast, open-pit coal mine in the Cerrejon region, where rock formations are being exposed all the time — and sure enough, says the University of Florida scientist, “I started finding them immediately. Giant turtles, strange, crocodile-like things — hundreds of specimens.”

But it was only a couple of years ago that he made the most extraordinary discovery of all — not in the coal mine, but back at the Florida Museum of Natural History, where the fossils were being stored. “A grad student was looking at some bones labeled ‘crocodile,’” he says, “and realized they weren’t from a crocodile at all.” They were from a snake — and it was far bigger than any snake that had ever been seen. According to Jason Head, of the University of Toronto, who co-authored a paper with Bloch and several others in this week’s Nature, the monster, which lived during the Paleocene period about 58 million years ago, stretched 45 ft. or more from head to tail and weighed in at about a ton.

Perhaps the most surprising part of all, though, is that while the discovery is important to evolutionary biologists, it may be even more important to climate scientists who are struggling to understand what’s in store as the Earth’s temperature continues to rise. It turns out that the bigger the snake, the warmer an environment it needs to survive. So using a standard formula that relates temperature to body weight, the scientists calculated that the giant snake, which they named Titanoboa cerrejonensis, must have slithered around in average year-round temperatures of about 30-34 C, or 86-93 F, compared with 28C/82F today.

That might not seem like a surprise, given that we already know the Earth was much warmer back then; fossils from the same period have proven that places like Greenland were tropical paradises. But climatologists have wrestled for years with the question of how that warmth was distributed. Did the Arctic and Antarctic warm up to match the tropics, so that the whole planet was uniformly balmy? Or did both warm equally, so that the poles got warm while the tropics got stifling?

If Titanoboa is any measure, it’s the latter—which means our own climate future could look the same.  “This is a big extrapolation,” warns Head, “based on very little data, so you need to take it with a huge grain of salt at this point. It's a coarse inference of what might happen, but it’s very hard to predict.” If it does happen, though, the fact that such mammoth snakes went extinct millions of years ago might not be such a consolation. “Temperatures like this are within the range of projections for the next hundred years. Of course, in the Paleocene snakes had millions of years to adapt to changes in temperature, so it’s an open question whether snakes could get that big that quickly. But it’s certainly possible”