Chickens, Eggs, and Molecular Evolution

Which came first, the chicken or the egg? How about neither?

According to a recent study by scientists, modern life may have evolved in a series of energetically favorable reactions, as opposed to the RNA World or Metabolism-first hypotheses.

The scientists, biology researchers at George Mason University, believe that their explanation of the beginning of life is more likely than other hypotheses because it does not require the assembly of extremely complex organic molecules (like RNA) by sheer chance.

In molecular biology, nucleic acids like DNA and RNA are the "egg." Nucleic acids allow for the synthesis of enzymes that drive metabolism (the "chicken").

In their paper, the scientists compare the evolution of complex life to the flow of water down a hill.

"Imagine a large pond of water sitting on top of a hill," the scientists wrote. "We know that there are any number of other states—any in which the water is lower than it is at the top—which have lower energy and are therefore states toward which the system will tend to evolve over time."

They go on to liken the evolution of complex biochemical pathways to the formation of channels through which the water can flow to the bottom of the hill. Eventually, a complex system of waterways forms to carry the water, analogous to the formation of complex biochemical interactions in modern lifeforms.

If the biologists' theory gains traction, it could prove one of the biggest paradigm shifts in the field since the Miller-Urey experiment.



Source: http://www.americanscientist.org/issues/feature/2009/3/the-origin-of-life/1