How long ago did life begin on earth?
Estimates: Oxygen appeared on Earth 2.4 billion years (BY) ago; unicellular to multicellular evolution 2 BY - 0.6 BY ago.
Estimates: Yet to be confirmed is that some life-form might have
existed before oxygen appeared upon Earth.
Oxygen appeared on Earth about 2.4 billion years (BY) ago.
Unicellular to multicellular evolution by about 2 BY - 0.6 BY ago.
Sea life came a little later..
This was followed by leg-bearing worms, and so on.
Human-resembling anthropoid appeared by about 0.047 BY (47 million years)