Earth's fossil record shows that Earth had a period before life existed, followed by a point where microbial life was present. What happened? Abiogenesis is the scientific hypothesis that life on Earth may have originated from nonliving matter.
The concept of abiogenesis suggests that the first living organisms arose when simple molecules, including water, combined to form simple organic compounds, such as amino acids, through a gradual process of increasing complexity. There are different ideas about what environments may have supported this process. One theory is that it occurred in deep-sea hydrothermal vents. Another is that it may have occurred in icy or frozen regions of early Earth. The word abiogenesis is built from Greek roots: a-, meaning "not," bio-, meaning "life," and genesis, meaning "origin."