Charles Darwin, in an insightful letter to his friend Joseph Hooker in 1871, proposed that life may have begun on land, in:
“…some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc. present, that a protein compound was chemically formed, ready to undergo still more complex changes. At the present day, such matter would be instantly devoured, or absorbed, which would not have been the case before living creatures were formed.”
With the 1977 discovery of deep-sea hydrothermal vents and their abundant web of life based on micro-organisms that thrive solely on chemical compounds (no sunlight involved), the prevailing view on where life may have originated changed from a terrestrial to a deep marine setting.
However, the pendulum is swinging back to Darwin’s original idea. It turns out that the oceans are too salty, too wet, and too dilute to make the complex chemistry required for life to get started. However, Darwin’s model has been slightly modified; instead of a single pond, research now suggests that a field of closely spaced and chemically diverse hot springs – such as those found in New Zealand’s Taupo Volcanic Zone, or in Yellowstone National Park in the USA – would be able to concentrate the necessary ingredients for life and promote the formation of complex organic compounds. The discovery of microbially-inhabited and chemically diverse fossilised hot springs in 3.5-billion-year-old rocks of the Pilbara Craton of Australia provided evidence that supports an origin of life on land hypothesis, with important implication in the search for possible ancient life on Mars.