In the author's model, progenotes were very unlike modern cells, their component parts with different ancestries, and the complexion of their components changing drastically over time. According to the author, the transition from progenotes to genotes turned upon the evolution of translation, the conversion of messenger RNA code into the specific amino acid sequences of specific proteins. The ancestor cannot have been a particular organism, a single organismal lineage. The universal ancestor is not an entity, not a thing. It is a process characteristic of a particular evolutionary stage.
Prokaryotes are cells without a cell nucleus and other membrane-bound organelles.
The process is common among primitive life forms such as bacteria. Catalysis at mineral surfaces might generate replic- ating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. But many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. In 1953, the chemist Stanley Miller reported what soon became a famous experiment. To water under a gas mixture of methane, ammonia, and hydrogen, he added an electrical discharge.