The first natural thing on earth - it's a matter which can have a lots of opinions and this might can also lead to a debate. The first living thing on earth must be the most simple one . The left ones have originated from it. So the most scientists are having an opinion that the bacteria and other single celled ones are the most primitive ones on earth. They have an opinion that bacteria have originated in oceans and as the time passed they have underwent evolution to form multicellular ones.