Life on Earth really did start on land in a "warm little pond" and not in the oceans - just as Charles Darwin said more than 140 years ago
Like the hot springs and geysers of Yellowstone National Park today - volcanic processes actively vented vapour from the planet's interior Photo: ALAMy
The first primitive cells germinated in pools of condensed vapour caused by underground hot water or steam bubbling near the surface of the planet, a study shows.
The finding published in Proceedings of the National Academy of Sciences challenges the widespread view that life originated in the sea.
Researchers analysed evidence of key rock chemicals in ancient inland and marine habitats and compared them with a genetic reconstruction of Earth's first cells.
Physicist Professor Dr Armen Mulkidjanian and colleagues discovered the oceans did not contain the best balance of ingredients to foster life.
Instead the simplest cells assembled in inland "hatcheries" where - like the hot springs and geysers of Yellowstone National Park today - volcanic processes actively vented vapour from the planet's interior.
The chemical composition of these emissions most closely matches the inorganic chemistry of cells, said the researchers.
They said these "cradles of life" share all of the advantages of the deep sea hydrothermal vents that have been previously proposed in the same capacity including the presence of organic matter.
Prof Mulkidjanian, of Osnabruck University in Germany, said: "In addition - and in contrast to deep sea vents - terrestrial geothermal fields are conducive to condensation reactions and enable the involvement of solar light as an energy source."
If this vapour condensed into ponds lined with the right terrestrial minerals the environment would have provided a natural starting point for cells to evolve essential biochemical processes.
Conceptually similar to the central idea in Darwin's theory, the model in the study proposes life on Earth originated on land and subsequently invaded the oceans.
In 1871 the legendary naturalist suggested in a letter to English botanist Joseph Hooker that the original spark of life may have begun in "a warm little pond."
Prof Mulkidjanian said under this scenario the ocean was invaded by life at a later stage following the emergence of chemical membranes.
He said: "Geochemical reconstruction shows the ionic (chemical) composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapour-dominated zones of inland geothermal systems.
"The pre-cellular stages of evolution might have transpired in shallow ponds of condensed and cooled geothermal vapour that were lined with porous silicate minerals mixed with metal sulfides and phosphorous compounds."
The commonly-held belief has been the first microbes originated at the bottom of the ocean in black smoker chimneys formed around deep-sea hydrothermal vents.