Abiogenesis

Abiogenesis (/ˌeɪbaɪ.ɵˈdʒɛnɨsɪs/ AY-by-oh-JEN-ə-siss) or biopoiesis is a natural process by which life arises from simple organic compounds. The earliest known life on Earth existed between 3.9 and 3.5 billion years ago, during the Eoarchean Era when sufficient crust had solidified following the molten Hadean Eon.

Scientific hypotheses about the origins of life may be divided into several categories. Most approaches investigate how self-replicating molecules or their components came into existence. For example, the Miller–Urey experiment and similar experiments demonstrated that most amino acids, often called "the building blocks of life", can be racemically synthesized in conditions thought to be similar to those of the early Earth. Several mechanisms have been investigated, including lightning and radiation. Other approaches ("metabolism first" hypotheses) focus on understanding how catalysis in chemical systems in the early Earth might have provided the precursor molecules necessary for self-replication.