New research suggests that large alkaline soda lakes may have been the cradle of life on early Earth, offering a solution to the long-standing puzzle of how sufficient phosphorus was available for life to emerge. Craig Walton, a geochemist at ETH Zurich, along with an international team of scientists, proposed that these mineral-rich lakes provided the high concentrations of phosphorus necessary to initiate the chemical reactions that gave rise to life.
Phosphorus is a critical element in biology, forming the backbone of molecules like DNA, RNA, and ATP. However, its scarcity in both the ancient environment and today puzzled scientists for decades. Laboratory experiments demonstrated that prebiotic chemistry requires phosphorus concentrations about 10,000 times higher than what naturally occurs in water. This raises a fundamental question: where did early life obtain the necessary phosphorus?
Walton and his colleagues believed that large soda lakes, such as California's Mono Lake, could hold the key. Mono Lake, known for its unusual chemistry, has no natural outflow; water exits only through evaporation, leaving behind phosphorus and allowing it to accumulate to high concentrations. “The phosphorus of Mono Lake is therefore retained in high concentrations,” Walton explained.
In these alkaline, mineral-rich lakes, phosphorus could have accumulated to levels sufficient to support the chemical reactions necessary for the origin of life. Unlike smaller lakes, where the phosphorus supply would be quickly depleted as life developed, large soda lakes without natural runoff could maintain high phosphorus concentrations over a long period. That would have been crucial, as the availability of phosphorus regulates the growth and metabolic activity of organisms.
The unique conditions of soda lakes—strongly alkaline environments with pH levels ranging from 9 to 12 and high concentrations of carbonate salts like sodium carbonate—could have created ideal settings for prebiotic chemistry. These environments allow minerals and molecules to accumulate in sufficient concentrations, providing the chemical building blocks for biomolecules and cells.
The theory challenges earlier assumptions about the origins of life, including those of Charles Darwin, who suggested that life may have begun in small, warm ponds. Walton's research indicates that life is more likely to have originated in large bodies of water with sustained high levels of phosphorus, such as soda lakes.
Building upon earlier suggestions that soda lakes could be the cradle of life, Walton examined the role of high phosphorus concentrations in these environments. His geochemical analyses substantiate the theory that large soda lakes provided the necessary conditions for life to emerge.
Mono Lake, despite its salty and alkaline nature, supports a variety of microorganisms. It is a hypersaline body of water containing large volumes of sodium chloride and other dissolved salts. Inflowing river water brings in phosphorus, and evaporation prevents its loss, allowing it to build up over time. “Since phosphorus does not evaporate easily, it stays behind and accumulates in the lake,” Walton noted.
Walton emphasized that certain conditions, including sufficient phosphorus, are needed to trigger the processes that lead to life. Large soda lakes would have had phosphorus concentrations high enough to sustain both the basic chemical reactions and life over the long term, providing an environment where necessary minerals and molecules could accumulate, setting the stage for the origin of life.
The article was written with the assistance of a news analysis system.