Unit: History of life on Earth
How did Earth form, and what were early life forms like? Learn what we do (and don't!) know about the origins of our amazing planet and the dawn of its diverse inhabitants.
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!).
Short videos from 23 and Me, describing events from human prehistory.