Big Little Big
At the start of the Eocene Epoch, about 55.5 million years ago, Earth experienced perhaps the most sudden and extreme warming at any time in its history. This planetary heatwave is called the Paleocene-Eocene Thermal Maximum, or PETM. Scientists, like Phil Gingerich at the University of Michigan, have found evidence that the PETM was associated with a major release of carbon dioxide into the environment, much as is happening with burning fossil fuels today. What we learn from studying the PETM may help us understand our own future.
The PETM had dramatic effects on plants and animals. Warmth-loving species migrated toward the poles, and some even extended their ranges across the Arctic to new continents. Some animals evolved smaller bodies. Fossil jaw bones show that a hoofed plant-eating mammal called Ectocion that lived in Wyoming was smaller (center) during the PETM than its relatives living before or after (bottom and top, respectively).