LIFE is likely to have emerged in warm puddles of fresh water and not the piping-hot volcanic springs that have often been proposed as its source, research has suggested.

An experiment to re-create the conditions in which life began has revealed that the hot, acidic, clay-filled waters that had been proposed as prime candidates are probably incapable of mixing organic matter in the right way.

The idea that the origin of life might be traced to ponds warmed by volcanic heat, or around underwater hydrothermal vents, was first put forward by Charles Darwin in a letter in 1871, and the theory became accepted as one of the most likely explanations. It suggested that a combination of organic compounds such as amino acids, acidic waters rich in clay and heat, could have led to the formation of the complex molecules that kick-started life.

A team led by David Deamer, of the University of California, at Santa Cruz, has put this hypothesis to the test by investigating volcanic springs of this sort in Kamchatka, in Russia, and Mount Lassen, in California. He found that contrary to expectations, these springs were poor environments for the formation of these molecules.

When organic material was added to the pools, the clay particles attached themselves to it and prevented the chemical reaction that could be important to the formation of life.

The findings, which will be presented today at a Royal Society conference in London, suggest that life is more likely to have emerged in shallow, cooler pools of fresh water.These would have been of neutral pH, with a less intense heat source, and the water would have evaporated frequently, concentrating organic material.

“It is about 140 years since Charles Darwin suggested that life may have begun in a ‘warm little pond’,” Professor Deamer said. “We are now testing Darwin’s idea, but in ‘hot little puddles’ associated with the volcanic regions of Kamchatka and Mount Lassen. The results are surprising and in some ways disappointing. It seems that hot acidic waters containing clay do not provide the right conditions for chemicals to assemble themselves into ‘pioneer organisms’. We found that organic compounds such as amino acids and the bases of DNA, which are the building blocks for life, became strongly held to the surfaces of clay particles in the volcanic pools in Kamchatka. Phosphate, another essential ingredient for life, also became held to the surface of the clay. We saw the same thing in a boiling pool at Mount Lassen.

“In our experiments, the organic compounds became so strongly held to the clay particles that they could not undergo any further chemical reactions. In addition, when we introduced soap-like molecules into the pools, they did not form membranes, which would be required to form cells.”

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