In an Early Edition Open Access article in PNAS “Origin of first cells at terrestrial, anoxic geothermal fields” Mulkidjanian et al. explore geochemical evidence for the origin of life on our planet. They find that all cells contain much higher amounts of potassium, phosphate and transition metals than any modern environments such as lakes, rivers and oceans, or for that matter reconstructed ancient such environments. They speculate that these higher levels of various elements are an inherited reflection of the inorganic environment in which the primordial cells were once formed, and use the geochemical composition to investigate suitable “cradles for life”.
Their results point to an origin of life, not in the oceans as we are used to, but in anoxic geothermal/volcanic fields on land, where the right geochemical conditions could be found. They argue that such anoxic geothermal/volcanic field on land could stay more or less unaffected by variations in the primordial climate for millions of years, long enough not only to form these “protocells” but also to sustain evolution of the first life forms.
In contrast to deep sea hydrothermal vents, which have also been suggested as “cradles of early life on Earth”, geothermal fields on land where subjected to weak solar light from the young sun which would probably be of benefit to the process.
It is a very interesting theory.
So perhaps life as we know it began on land, moved into the sea, diversified, evolved and then moved back on land billions of years later…
But how, when and why did the evolution process move into the sea?