The Earth forms and is bombarded by meteorites and comets.

Land plants evolve, drastically changing Earth's landscape and creating new habitats.

The supercontinent called Pangea forms. Conifer-like forests, reptiles, and synapsids (the ancestors of mammals) are common.

In Africa, an early hominid, affectionately named "Lucy" by scientists, lives. The ice ages begin, and many large mammals go extinct.

Anatomically modern humans evolve. Seventy thousand years later, their descendants create cave paintings — early expressions of consciousness.