Question

When did life begin?

Answer 1

At least `3.8` billion years ago.

Explanation:

The earliest direct evidence we have of life on Earth is about `3.8` billion years old. We also have rocks dating back `4` billion years with inclusions as old as `4.4` billion years, but the evidence of life in these samples is circumstantial and may have other causes.

There is speculation as to whether life began outside our solar system and seeded life here. In particular the Panspermia theory is that life is everywhere in the Universe, having begun shortly after the Big Bang `13.8` billion years ago, seeded into our solar system in the form of extremophiles (small organisms that survive harsh conditions).