■ Around 3.7 billion BC Traces of Greenland's life activity

Life can be seen hundreds of millions of years after the birth of the earth. Life was born in the sea. The next image on the left is a rock containing Greenland's stromatolite. A structure (triangle in the center) that seems to be a trace of life activity discovered 3.7 billion years ago.

Stromatolites are formed by the formation of layers of sediment by microorganisms such as bacteria. This layer becomes rock over many years. The rock itself is not a living thing, but it indicates that there was a very simple unicellular organism that made the rock. Allen Natman of the University of Ulongong, Australia, who led the study, said these fossils show that life was born relatively soon after the Earth was formed 4.5 billion years ago.