1. Prehistoric evolution began around 3.5 billion years ago with the emergence of the first single-celled organisms.
2. The first multicellular organisms appeared around 1.2 billion years ago.
3. The first animals appeared in the fossil record around 600 million years ago.
4. The first primates evolved around 55 million years ago.
5. Homo sapiens, the species to which modern humans belong, evolved around 200,000 years ago.
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