The Quaternary is the most recent geologic period. The glaciations that characterise this period began about 2.6 million years ago. There have been roughly 50 glacial–interglacial cycles during the Pleistocene Epoch which comprised all of the Quaternary except the current interglacial interval, the Holocene. Pleistocene biota mostly responded to the series of rapid dramatic climatic changes by migrating to regions of acceptable climate. The constant reshuffling of biological communities led to the formation of many combinations of species for which there is no modern analogue. The end of the last glaciation saw the extinction of large numbers of large mammals (the Pleistocene megafauna) in Eurasia, Australia and the New World. The Late Pleistocene saw the rise and geographic dispersal of humans, including Neanderthals in Europe and southwest Asia, and modern humans who spread out of Africa into Europe, Asia, Australia and eventually the New World.

Key concepts:

• Rapid climate change characterised most of the Quaternary.
  
• The Quaternary and Late Tertiary saw the evolution of modern ecosystems.
  
• Nonanalogue biological communities formed during the Pleistocene, as the ranges of individual species responded independently to climate change.
  
• The Late Pleistocene–Holocene transition saw a major extinction event among megafaunal mammals.
  
• The Pleistocene was also the most important interval of human evolution and dispersal.