Eocene

Eocene is a geologic epoch that lasted from about 56 to 33.9 million years ago. During this time, the Earth’s climate was warm and hospitable, allowing for the spread of life across the globe. The Eocene is often considered to be a golden age for mammals, as many new species emerged and thrived during this time. Among them were early primates, horses, and rodents. The Eocene also saw the rise of the first modern humans, Homo sapiens sapiens.

The Eocene epoch began with the Paleocene-Eocene Thermal Maximum (PETM), a sudden warming event that caused global temperatures to increase by 5–8°C (9–14°F). This rapid change in temperature had profound effects on ecosystems around the world; many tropical species expanded their ranges into higher latitudes while others went extinct. The PETM is thought to have been caused by a release of methane gas from hydrate deposits in ocean sediments. This greenhouse gas trapped heat in the atmosphere and led to further warming over several thousand years.

The warm conditions of the Eocene were eventually brought to an end by another period of cooling known as the Oligocene Transition. This transition was marked by a decrease in atmospheric carbon dioxide levels, which allowed ice sheets to form at high latitudes. As global temperatures continued to decline through the Oligocene and Miocene Epochs, many tropical species perished while cooler-adapted forms took their place. By the end of the Miocene, Earth’s climate had reached its present state and has remained relatively stable ever since.