Early life forms on Earth, starting at least 3.7 billion years ago, were single-celled organisms (an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells). Such organisms (Prokaryotes, Protozoans, algae) multiply by fission into daughter cells. (Daughter cells are cells that result from a single dividing parent cell. Two daughter cells are the result of the mitotic process while four cells result from the meiotic process. For organisms that reproduce via sexual reproduction, daughter cells result from meiosis); thus do not age and are potentially immortal under favorable conditions.
