Paleogene

The Paleogene period marks a time of recovery and diversification. Following the mass extinction at the end of the Cretaceous, mammals began to evolve rapidly. The early Paleocene saw small, generalized mammals that evolved into a wide array of forms by the Eocene, including early primates, ungulates (hoofed animals), and cetaceans (whales). Birds also diversified significantly during the Paleogene, with many modern bird groups appearing.

The Paleogene climate was initially warm, with the early Eocene marking one of the hottest periods in Earth’s history—the Paleocene-Eocene Thermal Maximum (PETM). This event was characterized by a rapid rise in global temperatures and is believed to have been caused by a massive release of carbon into the atmosphere, possibly from volcanic activity or methane clathrate release. The PETM had profound effects on life, driving evolutionary changes in both terrestrial and marine species.

By the Oligocene, however, the Earth began to cool, and the Antarctic ice sheet started to form. This cooling trend continued into the Neogene, leading to the establishment of the modern polar ice caps and setting the stage for the ice ages of the Quaternary.