The last universal ancestor (LUA), also called the last universal common ancestor (LUCA), cenancestor, or progenote, is the most recent organism from which all organisms now living on Earth have a common descent. Thus it is the most recent common ancestor (MRCA) of all current life on Earth. The LUA 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 biogenic graphite found 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.