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Unit: History of life on Earth

Life began on Earth at least 3.5 billion years ago. Since then, it's diversified in an amazing way! Learn about important events in the history of living organism on Earth, up to and including the appearance of humans.
Geologists and archaeologists will tell you how old things are or when they happened, but how do they know? This tutorial covers some of the primary techniques of "dating" (in the geological, not the romantic, sense!).

About this unit

Our planet has an amazing history spanning about 4.5 billion years! Learn more about how Earth formed, the early history of life on Earth, and the origins of humans.