In the natural sciences, abiogenesis, or "chemical evolution", is the study of how life on Earth could have arisen from inanimate matter. It should not be confused with evolution, which is the study of how groups of living things change over time. Amino acids, often called "the building blocks of life", can form via natural chemical reactions unrelated to life, as demonstrated in the Miller�Urey experiment, which involved simulating the conditions of the early Earth. In all living things, these amino acids are organized into proteins, and the construction of these proteins is mediated by nucleic acids. Thus the question of how life on Earth originated is a question of how the first nucleic acids arose.
