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From fossil evidence, it appears that life may have existed on Earth as early as 3.5 billion years ago. This suggests that life must have evolved sometime during Earth's tumultuous first billion years.
Scientists discover potentially oldest signs of life on Earth â 3.5 billion-year-old microbe traces in rocks in Australia. Evidence of the complex microbial ecosystem was found in sedimentary rocks in the remote Pilbara region in Western Australia Photo: Alamy. By Jonathan Pearlman, Sydney. 9:13AM GMT 13 Nov 2013. Comments. Scientists have discovered possibly the earliest signs of life on Earth â remains of bacteria that are almost three-and-a-half billion years old â in a remote region of north-west Australia.