Question

When did life on our planet begin?

Answer 1

The best estimate right now is some time older than 3.5 billion years ago. A recent 2015 paper suggested an even older time of 4.1 billion years -did-life-begin-earth-300m-years-earlier-previously-thought-study-finds-2148478

Explanation:

But, as life made the transition from inorganic chemistry to organic -life chemistry its a little unclear during that time exactly what life is and how you define it! The oldest undisputed fossils are cyanobacterias matts at about 3.5 billion years old from Australia.

http://www.livescience.com/41191-ancient-microbe-fossils-found.html