Era · Before c. 3000 BC
From the formation of Earth and the age of dinosaurs to the first cave art and monuments, before writing was invented.
Climate, ocean chemistry and oxygen levels stayed relatively stable for roughly a billion years while eukaryotes diversified only slowly, before the upheavals of the Neoproterozoic.
Most of Earth's continental crust was joined in one landmass, whose breakup opened new oceans and may have helped trigger the Cryogenian Snowball Earth glaciations.
The fossil red alga provided the oldest widely accepted evidence of sexual reproduction, complex multicellularity and a eukaryote belonging to a living group.
Two long glaciations, the Sturtian and the Marinoan, covered much or all of the oceans in ice before greenhouse warming ended them, setting the stage for the Ediacaran Period.
Phosphatised microfossils revealed cell-level detail from the Ediacaran Period, fuelling a debate over whether they include the oldest known animal embryos.
Rock surfaces at Mistaken Point preserve some of the oldest known communities of large, complex organisms, recognised as a UNESCO World Heritage Site in 2016.
The first assemblages of large, multicellular organisms appeared in the oceans, including some of the earliest animals, before most forms vanished near the start of the Cambrian.
The fossil, named Charnia masoni in 1958, was the first complex fossil found in rocks already known to be Precambrian, proving that large organisms lived before the Cambrian.
Molecular traces of cholesterol showed that Dickinsonia was an animal, one of the oldest known in the fossil record.
Gondwana assembled by about 500 million years ago, joined Pangaea, and broke apart from about 180 million years ago into today's southern continents.
Life spread from the sea onto land and diversified enormously before the era ended with the largest mass extinction in Earth's history.
Within some 20 to 30 million years, most major animal body plans, including arthropods, molluscs and chordates, appeared in the fossil record.
