Day--13

Earth perhaps played host to very diverse sorts of life since the early stage of its formation.

This paper states that these aspects of  issues, namely, that the  one is stromatolites; the other is what Dr. P found in Quebec.

The former contends that small, layered mounds produced by photosyntheising bacteria 3.7 billion years old. The latter claims that the signature of living organisms is in rocks from Quebec between 3.8-4.3 billion years ago. Similar rosette-shaped features have been found in younger, but still ancient, rock formations from Biwabik etc.  Meanwhile, they don't undergo photosynthesis process.