The Precambrian was the first supereon in Earth's history, lasting from the formation of the Earth to the Cambrian period. During this time, the Earth's atmosphere was high in sulphur and carbon dioxide, consisting of a green, fog-like sulphuric gas, and Precambrian Worms thrived.

Visits and incursions

Episode 2.2

An Anomaly to the Precambrian opened in an inner-London office block in the present day, and the Precambrian atmosphere's sulphuric gases and dozens of Precambrian Worms came through. The Worms perished when high temperatures forced the Precambrian gas out of the building.

Episode 5.5

During Convergence in 2011, an Anomaly to the Precambrian opened up in an Infant School classroom, and the Precambrian atmosphere and an unknown number of Precambrian Worms came through into the classroom. The Worms were presumably either returned through the Anomaly or killed by one of the ARC teams.

Real life

The Precambrian lasted from 4600 to 541 million years ago; beginning with the formation of the Earth, and ending with the Oxygen Catastrophe. Very little is known about the Precambrian, although it is believed that its atmosphere was high in CO2 and nitrogen and had no oxygen content. It is also believed that there were a number of glacial periods during the Precambrian, and possibly even a 'Snowball Earth.' It is widely thought that there were small proto-continents on Earth, which collected into a single supercontinent 1 billion years ago, before breaking up 600 million years ago. Bacterial and protozoan life thrived in the Precambrian, but there is believed to have been no complex, multicellular life, such as plants or animals.


  • The Precambrian is the furthest back in time that any known Anomaly has ever opened to.
  • The Precambrian fog is darker in Series 5 than in Series 2.
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