“For the past 9 years, we’ve been slowly, slowly collecting teeth, and sometimes more than teeth, fragmentary jaws, of the first horses to come in. And what we started to find was something pretty surprising to us. We had known that the horses that came in initially with that event 56 million years ago were very small, about the size of a small dog. But what we didn’t realize was that in fact when they came in they were a little bit larger than we had expected; and that through the climate event they became about 30 percent smaller and then became larger again,” he said.

Then, Bloch said, fellow researcher Ross Secord, now at the University of Nebraska, took a closer look at what are called oxygen isotopes. These were found in the teeth of the horses. The relationship between oxygen and carbon in these isotopes can provide much information.

“What he showed was that exactly coincident with this body size change that we had documented there were shifts in the oxygen isotope that showed it was getting warmer as the horses were getting smaller. And then as the horses became larger again it became cooler,” he said.

They concluded that temperature change resulted in smaller horses.

Climate itself is changing through this interval by as much as 10 degrees [Celsius] at high latitudes and perhaps as low as 5 degrees in lower latitudes. So that’s a large scale event and it starts to put us in the range of the kind of climate shift that is being predicted by climate models today say for the next 100 years.