Hot pore systems heated by volcanic activity may have harbored the first life on Earth, with conditions promoting the cyclical replication and emergence of nucleic acids, a new study says.
In order for life to flourish on Earth, one critical precondition is that simple biomolecules must have the opportunity to form more complex structures, which can then reproduce themselves and store genetic information in a chemically stable form.
However, in order for this scenario to work the precursor molecules have to build up in a highly concentrated form in solution. On early Earth, oceans would have had such molecules in extremely low concentrations - too low to harbor life. But now new research finds that water-filled micropores in hot rock may have had just the right concentrations.
Through a series of experiments, the researchers found that these pore systems, located on the seafloor, were heated by volcanic activity to the point that they acted as nurseries for the synthesis of RNA molecules - important carriers of our hereditary information.
"The key requirement is that the heat source be localized on one side of the elongated pore, so that the water on that side is significantly warmer than that on the other," Dieter Braun of Ludwig-Maximilians-Universität München in Munich explained in a statement.
This is the result of a process called thermophoresis, during which charged molecules in a temperature gradient preferentially move from a warmer to a cooler region. This allows longer polymers to become trapped, an important factor in the evolution of nucleic acids such as RNA and DNA. That's because longer molecules can store more genetic information.
"Life is fundamentally a thermodynamic non-equilibrium phenomenon. That is why the emergence of the first life-forms requires a local imbalance driven by an external energy source - for example, by a temperature difference imposed from outside the system," Braun said.
Researchers found that not only are nucleic acids retained in the studied pore systems, they are also capable of replication under these conditions. And when the nucleic acids accumulate to levels beyond what the pore is able to store, newly replicated molecules can escape and colonize neighboring pore systems.
These results, described further in the journal Nature Chemistry, shed some light on the conditions it took for life to propogate on Earth and lead to the more complex organisms, such as humans, that we see today.
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