# When was life formed on earth?

Apr 19, 2018

A few thoughts...

#### Explanation:

The earliest definitive evidence of life on Earth that we have is probably stromatolite fossils from about $3.7$ billion years ago.

Other discoveries of apparent remains of life processes has been dated to between $4.1$ and $4.28$ billion years ago. We cannot be sure that these remains were generated by biological processes, so this evidence is less conclusive.

We could also question what we mean by life. For example, prior to cellular life there may have been self replicating strands of RNA supported by other proteins.

So what we can say is that life appeared on Earth at least $3.7$ billion years ago and probably somewhat earlier.

Whether it formed on Earth is an interesting question. There are various theories that place the origin of life outside Earth, with either primitive life or its precursors arriving on Earth via meteorites, comets or similar.