Question

When did simple life begin on earth?

Answer 1

Around 3.8 billion years ago.

Explanation:

Life evolved from early organic compounds that eventually came together to form the first simple "pre-cells". Pre-cells evolved into the first anerobic (oxygen deficient) single celled bacteria. These simple bacteria would continue to be the dominate life form for on Earth for over 1 billion years until the first photosynthesizing bacteria evolved.