Archean era

Archean era

3800 BCE

It was during the Archean era that life first arose on Earth. At this time there were no continents, just small islands in a shallow ocean. There was a vast amount of carbon dioxide in the atmosphere, but since the sun was much fainter back then, the combined effect did not raise Earth's temperature to an extreme. Such levels of carbon dioxide would be toxic to the majority of animals alive today - as would the low oxygen levels.

Cryogenian period

850 BCE

A succession of incredibly harsh ice ages waxed and waned during the Cryogenian. It is nicknamed Snowball Earth as it's been suggested that the glaciation was so severe it may even have reached the equator. Life during the Cryogenian consisted of tiny organisms - the microscopic ancestors of fungi, plants, animals and kelps all evolved during this time.