Environment and evolution through the Paleocene–Eocene thermal maximum

The modern orders of mammals, Artiodactyla, Perissodactyla and Primates (APP taxa), first appear in the fossil record at the Paleocene–Eocene boundary, c. 55 million years ago. Their appearance on all three northern continents has been linked to diversification and dispersal in response to rapid environmental change at the beginning of a worldwide 100 000–200 000-year Paleocene–Eocene thermal maximum (PETM) and carbon isotope excursion. As I discuss here, global environmental events such as the PETM have had profound effects on evolution in the geological past and must be considered when modeling the history of life. The PETM is also relevant when considering the causes and consequences of global greenhouse warming.