The Neogene period is a division of earth’s history spanning from around 23 to 0.05 million years ago, and during which the global climate gradually cooled. The continents were largely in their modern positions. One major geographic change was the closure of a seaway known as the Isthmus of Panama when South and North America became connected. This land bridge diverted warm waters northwards, forming the Gulf Stream, and allowed the migration of animals between North and South America. As a result of a cooler global climate, tropical rainforests gradually gave way to grasslands. It was in this environment that the first hominids evolved in Africa and began to spread across the world. The end of the Neogene is marked by the establishment of the glacial conditions, characteristic the Quaternary.
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