Day 77: Early Life

So first off, while the earliest form of life is firmly believed to have begun about 3.7-3.8 billion years ago, scientists recently went from believing the eukaryotic life existed 1.56 billion years ago to 2.3 billion years ago. Which is when the Great Oxidation Event took place. So it makes sense to think that evolution into life as we know it today began then. Given that the enzymes we require now need oxygen and they could be traced back 2.3 billion years.

This somewhat marks the beginning of the Proterozoic Eon (2.5 billion years ago) which basically means “early life” eon. The atmosphere during this period is the oldest version of the one we are left with now. It is the third atmosphere overall, and the one that’s lasted all these years.

Plants, animals and some are forms of fungi are all believed to been formed during this period. But the early and late parts of the eon might have gone through “Snowball Earth” periods, which is the entire planet being subzero. It is believed that these periods happened prior to the Cambrian Explosion and might actually be what may have triggered the evolution of multicellular organisms. While there is a bit of a dispute surrounding this hypothesis saying that life would’ve ceased to exist as complete glaciation meant a huge dip in oxygen, recent findings along with research into possible life-forms on Mars do indicate that life in the water, under the ice, would’ve gone on with no disruption.