The Pliocene is a geological epoch that lasted from about 5.3 to 2.6 million years ago. It is part of the Neogene period and is characterized by significant changes in climate and the development of modern ecosystems. During this time, the Earth's climate became cooler and drier, leading to the expansion of grasslands and the decline of forests in some areas. This epoch is notable for the evolution of many species, including early ancestors of humans, such as Australopithecus. The Pliocene also saw the rise of large mammals, including mastodons and saber-toothed cats, as well as the formation of the Isthmus of Panama, which connected North America and South America.