The age of the Earth was determined by using absolute dating of
meteorites and moon rocks, which gives a date of 4.5 billion years old.
The oldest known Earth rocks are younger, at just more than 4 billion
years in age. Older Earth rocks have been destroyed by meteorite
impacts, weathering, or metamorphism.
The oldest known fossils are almost 3.8 billion years old. The oldest
fossils, however, are from very simple, single-celled forms of life.
They are far removed from the complex life forms of the present.
Multi-celled organisms (our likely ancestors) did not appear until
approximately 650 million years ago. These creatures likely gave rise to
animals with hard body parts (skeletons) about 560 million years ago.
Evolution of organisms has taken place in the last quarter of Earth’s
history, which includes the Paleozoic, Mesozoic, and Cenozoic
Fossils from Bitter Springs Formation
in Australia, oldest fossils known.