Origins of life. Artwork illustrating the theory that life on Earth originated around underwater volcanic vents called black smokers. Nine stages are shown here, from the atomic level to the cellular level. From bottom: prebiotic chemistry; amino acids, sugars and bases; more complex carbon compounds; formation of RNA (ribonucleic acids); formation of DNA (deoxyribonucleic acid). The evolutionary tree splits at this point into the routes that will form bacteria (left) and archaea (right). Each branch starts from a universal nucleic acid ancestor, followed by the formation of the cell wall, and finally, the bacteria and archaea breaking out of the black smoker wall to populate the Earth's oceans.