Question: how did life begin

Zoe Vance answered on 12 Mar 2025:

It’s a pretty hard question to answer! Life started about 3.5 or maybe even 4 billion years ago, depending on what evidence you believe to be evidence of life. Certainly we have evidence that certain bacteria (or something similar) were around at the 3.5 billion mark because they form big mats that actually leave fossil evidence, and something less complex would have to have existed earlier than those. Either way it’s a very long time ago to try and reconstruct what happened reliably but we have some ideas.

We know roughly what conditions looked like on earth at that time from very old rock that still preserves some of the chemicals that existed and also roughly what would be necessary for life to form in these conditions. Experiments suggest that the molecules we need for living things could have been created from the non-living chemicals that existed on earth at this time, though the exact mechanism is still debated a bit. A lot of people think that hydrothermal vents (undersea vents that blast out hot water with a lot of minerals in it) are a likely place for life to have started because early life evidence has been found around them and modern bacteria similar to the very ancient ones currently live there.

How we get from molecules to cells is also still debated. One idea is that RNA (similar to DNA) molecules were able to reproduce themselves and this began competition between the different molecules and started evolution off.