Phys.org noted a study published earlier this week by a University of Michigan paleontologist and his research team. They claim to have discovered a process of mammalian “dwarfing” that occurred during multiple climate warming events between 50 and 53 million years ago, and they say that it will probably happen again.

Paleontologists were relatively aware of the 55-million-year-old Paleocene-Eocene Thermal Maximum (PETM), after which the fossils of deer, horses, and primates became noticeably smaller. Professor of earth, environmental science, and team leader Philip Gingerich rewrote biological history when they discovered a second event, 2 million years after the PETM, that also affected body size.

“The fact that it happened twice significantly increases our confidence that we’re seeing cause and effect, that one interesting response to global warming in the past was a substantial decrease in body size in mammalian species,” he said. The Eocene Thermal Maximum 2 (ETM2) period lasted roughly 80,000 to 100,000 years, and the earth’s peak temperature rose about 5 degrees during that time.

Additionally, a report from NBC News about the impact of the study notes that a second, reptile-focused paleontologist studying the PETM found 60-million-year-old turtles the size of breakfast tables, and a snake referred to as a “Titanoboa” that stretched as long as a school bus.

Jonathan Bloch of the Florida Museum of Natural History paints a picture: “Imagine that the snake would have to squeeze through the door, and come up to your waist,” he said, all while horses were the size of housecats.

The terrifying conclusion of their study: because it’s happened not once but twice, it could absolutely happen again, and maybe a lot sooner than anyone would like. “You have to go back tens of millions of years before you get close to or higher than what we’re talking about for the next couple of hundred years,” Bloch said, referring to rising temperatures around the globe.

But Bloch remains confident that humanity might utilize tactics that the Earth herself used to rid the atmosphere of excess carbon dioxide. Who knows? Maybe, he suggests, the records of the PETM period could function as a “user’s manual for [Planet] Earth.”

[Image via Danielle Byerly/University of Florida]