Short answers, pulled from the story.
Abiogenesis, sometimes called biopoiesis, is the natural process by which life arises from non-living matter such as simple organic compounds. The prevailing scientific view is that it was not a single event but a process of increasing complexity, including the prebiotic synthesis of organic molecules, molecular self-replication, self-assembly, autocatalysis, and the emergence of cell membranes.
Based on the geologic record, life most likely emerged on Earth between 4.32 and 3.48 Gya. The earliest physical evidence reported in 2017 consists of microbialites in the Nuvvuagittuq Greenstone Belt of Northern Quebec, in rocks at least 3.77 and possibly as old as 4.32 Gya. The Earth itself formed at 4.54 Gya.
In 1952, Stanley Miller and Harold Urey showed that organic monomers such as amino acids could form spontaneously from inorganic precursors under prebiotic conditions. They used a highly reducing mixture of methane, ammonia, and hydrogen with water vapor. Later work found that current consensus describes the primitive atmosphere as weakly reducing or neutral, which reduces the variety of amino acids produced.
The RNA world hypothesis describes an early Earth with self-replicating and catalytic RNA but no DNA or proteins. It was proposed in 1962 by Alexander Rich, and the term was coined by Walter Gilbert in 1986. Many researchers agree an RNA world must have preceded modern DNA-based life, though it may not have been the first system to exist.
LUCA is the last universal common ancestor of all modern life-forms, a complex single-celled organism that lived over 4 Gya with hundreds of genes. A 2016 study identified 355 genes likely present in LUCA, suggesting it was anaerobic with a Wood-Ljungdahl pathway, nitrogen and carbon fixing, and thermophilic. A 2024 study inferred LUCA's age as around 4.2 Gya.
Several geological settings have been proposed, often in competition. The deep sea hydrothermal vent theory, advanced by William Martin and Michael Russell, places life at alkaline submarine vents, while other hypotheses favor surface bodies of water, hot springs similar to those at Kamchatka, icy environments, or inside the continental crust along tectonic fault zones.
Many organic building blocks have been found beyond Earth. The amino acid glycine was found in material ejected from comet Wild 2, and nucleobases including guanine, adenine, cytosine, uracil, and thymine have been found in meteorites. During the Late Heavy Bombardment, meteorites may have delivered up to five million tons of organic prebiotic material to Earth per year.