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0:00 /0:04 1× Here’s a quick scientific refresher: The funamental unit of any living organism is the cell. Some organismss, such as bacteria and algae have only one cell. Others—people, for instance—have billions of cells. Humans, plants, animals, bugs, and some single-celled organisms all

I am NOT Jeff Bezos. It is NOT 2006.

0:00 /0:04 1× c. 4.5 MYA Emergence of an early ancestor of modern humans, Ardipithecus ramidus, in Ethiopia. [ Olduvai Gorge, Ethiopia ] C. 4.2 MYA Earliest of the australopithecines ("southern ape-humans"), East Africa; walks on two feet, has a brain one-third the size