Proof of life?

1. Wrinkly laminations produced by life (below) vs the smooth layers of sediment with no life (above), all just a few centimetres across.

2. Wrinkly laminated and broad domical structures built by communities of microorganisms 3.48 billion years ago.

3. Tiny layered bumps in a rock hint at the presence of life – but how to know for sure? Detailed chemical analysis would have to be done in order to prove these structures were made exclusively by the activity of life.