GEOLOGY

Detailed explanation-1: -We know that life began at least 3.5 billion years ago, because that is the age of the oldest rocks with fossil evidence of life on earth. These rocks are rare because subsequent geologic processes have reshaped the surface of our planet, often destroying older rocks while making new ones.

Detailed explanation-2: -Researchers at UCLA and the University of Wisconsin–Madison have confirmed that microscopic fossils discovered in a nearly 3.5 billion-year-old piece of rock in Western Australia are the oldest fossils ever found and indeed the earliest direct evidence of life on Earth.

Detailed explanation-3: -The cyanobacteria have an extensive fossil record. The oldest known fossils, in fact, are cyanobacteria from Archaean rocks of western Australia, dated 3.5 billion years old. This may be somewhat surprising, since the oldest rocks are only a little older: 3.8 billion years old!

Detailed explanation-4: -Stromatolites were found to contain organic matter from 3.5 billion years ago. Scientists have discovered microbial remains in rocks that are 3.5 billion years old, showcasing some of the earliest signs of life on the planet.

Detailed explanation-5: -Scientists found fossilized prokaryotic cells in the rock that are able to grow and divide.