The Pliocene Epoch occurred between 5.3 and 2.6 million years ago. The global cooling trend continued, and the Earth's climate became more similar to what we experience today, with more pronounced seasons. A major geological event during this period was the formation of the Isthmus of Panama, a land bridge that connected North and South America for the first time. This new land bridge caused what is known as the Great American Interchange. Animals from North America, such as saber-toothed cats, wolves, and bears, moved south, while South American animals, like glyptodonts and ground sloths, moved north. This interchange led to many extinctions as new predators and competitors were introduced to different continents. It was also during the Pliocene that the first human ancestors, early hominins like Australopithecus, began to walk upright in Africa. The Pliocene was a transition period, leading directly into the dramatic climate shifts of the upcoming Ice Age.