Saturday, May 13, 2006


Thermodynamics and the Origin of Life

Two laboratories at Penn State have discovered a previously unknown biochemical process that became the inspiration for a fundamental new theory of the origin of life on Earth, reconciling a long-contentious pair of prevailing theories. This new, "thermodynamic" theory of evolution improves upon both previous theories by proposing a central role for energy conservation during early evolution, based on a simple three-step biochemical mechanism, according to a news release from Penn State.

James G. Ferry, Stanley Person Professor of Biochemistry and Molecular Biology, and Christopher House, Assistant Professor of Geosciences, at Penn State will announce their new theory in the June issue of Molecular Biology and Evolution. William Martin, editor-in-chief of that journal, says "The paper is a very significant contribution, and a wonderful example of interdisiplinary work as well."

"We've taken a new approach to thinking about the evolution of life from a thermodynamic perspective," Ferry says. "It reshapes the two previous theories of life's origin, it shows how they overlap, and it extends both of them significantly." The apparently irreconcilable "heterotrophic" and "chemoautotrophic" theories of the origin of life both focus on the processes by which chemical building blocks first appeared for primitive life to assemble into complex molecules. "But that's not really what the driving force was in early evolution," Ferry asserts. "Nobody had properly considered thermodynamics."

According to the heterotrophic theory, a primordial soup of simple molecules arose first, driven by nonbiological energy sources like lightning, and led eventually to primitive life forms. One difficulty with this theory is due to the huge variety and complexity of organic molecules that would have had to arise spontaneously. In contrast, the chemoautotrophic theory rests on the idea that primitive life forms themselves, perhaps associated with catalytic iron and sulfur minerals, gave rise to the first simple biological molecules. The obstacles to this theory are the large number of steps in the biochemical cycles that have been suggested, and the staggering structural complexity of the only known enzyme complexes that drive those reactions. Debate between the two camps has raged for two decades.

By studying a microbe that Ferry discovered thriving in the oxygen-free, carbon-monoxide-rich sediment beneath kelp beds, he and his group have helped to break this impasse. Life may have emerged in just such an environment, and this microbe's unique biochemistry may harbor the molecular fossil of the first metabolism on Earth.

Creationists and Intelligent design "theorists" often argue that the study of evolution leads to no practical results, but get this:

Their results also provide insights into the evolution of the microbial production of methane, the primary component of natural gas. A detailed understanding of methane biosynthesis could lay the foundation for a new alternative energy source, by raising the possibility of cost-efficient conversion of renewable biomass into clean fuel.


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