 Thus it is the most recent common ancestor of all current life on Earth.The LUCA is estimated to have lived some 3.5 to 3.8 billion years ago (sometime in the Paleoarchean era).The earliest evidence for life on Earth is graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.