Last Universal Common Ancestor
The last universal common ancestor (LUCA), also called the last universal ancestor (LUA), or the cenancestor, is exactly what it sounds like: the most recent common ancestor (MRCA) 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 LUCA would most likely be extremely simple, having only those properties which are shared by every living thing on Earth, whether they be humans or bacteria. Naturally, creationists deny any such thing exists.