A new study is out on global warming, and it’s making a doozy of a claim: the impact of climate change on human beings and every other mammal may mean we’re all going to shrink. The study says that past major warming events have resulted in significant amounts of dwarfism in mammals, and shorter periods of warming can also cause this effect.

Scientists based this extraordinary claim on their examination of bones from different “hyperthermal” periods. They started with the Paleocene-Eocene Thermal Maximum (PETM) and determined that in a period when the temparetures rose 9 to 14 degrees Fahrenheit, mammals got smaller by an astonishing 30 percent. They then looked at other warming events to see if there was similar shrinkage, and they were surprised at what they found.

By examining the molar teeth of bones from different warming periods, they were able to estimate body size, and found that two species shrank 14 and 15 percent. Scientists aren’t sure why this happens, but think it may have something to do that the CO2 levels caused the nutrients in plants to plunge, so mammals were having their growth stunted.

“We know that during the largest of these hyperthermals, known as the Paleocene-Eocene Thermal Maximum, or PETM, temperatures rose an estimated nine to 14 degrees Fahrenheit and some mammals shrank by 30 percent over time, so we wanted to see if this pattern repeated during other warming events,” says Abigail D’Ambrosia, a doctoral student at UNH and lead author of the study. “The hope is that it would help us learn more about the possible effects of today’s global warming.”