The late bombardment presents a problem. It seems either life was here when it happened, or it began shortly after. That seems to be still up in the air.
Quote: So Anbar, Arnold and Mojzsis were faced with seemingly contradictory evidence. Life appeared to have been flourishing during the period of the Late Heavy Bombardment, at a time when Earth's surface was thought to be uninhabitable. And traces of the bombardment were nowhere to be found in the Akilia rocks.