The Proterozoic eon covers almost two billion years, from 2.5 billion years ago to the start of the Cambrian 538.8 million years ago. Oxygen from photosynthesis built up in the air during the Great Oxidation Event, and cells with a nucleus, the eukaryotes, appeared.
Long glaciations known as Snowball Earth episodes marked the Cryogenian period, about 720 to 635 million years ago, and the era closes with the Ediacaran, which holds the first large soft-bodied animals.
Explore this era on the timeline
Key events of the Proterozoic
10 events are on the timeline for this era; these are among the most notable, in date order.
- from about 2.4 billion years ago to 2.1 billion years agoHuronian glaciation
- from about 2.4 billion years ago to 2.1 billion years agoGreat Oxidation Event
- from about 1.8 billion years ago to 800 million years agoBoring Billion
- about 1.65 billion years agoEarliest complex cells (eukaryotes)
- about 1.05 billion years agoEarliest complex multicellular life
- from about 717 million years ago to 661 million years agoSturtian glaciation (Snowball Earth)
- from about 650 million years ago to 635 million years agoMarinoan glaciation
- about 574 million years agoFirst large soft-bodied life (Ediacaran biota)
- about 543 million years agoCambrian explosion
- about 541 million years agoEnd-Ediacaran extinction