Many of nature's most dramatic processes, from lightning to hurricanes, exist simply because they are efficient ways of transferring energy. The basics of natural systems prefer that energy not wind up concentrated, but the vagaries of the planet make such concentrations inevitable. As a result, processes that involve otherwise unexpected order and energy become favored, simply because they are efficient means of shifting energy back into balance. A new proposal (which I discovered via the Panda's Thumb) suggests that some of the basics of life may simply have been a response to energy imbalance.
The paper, which is currently a working draft, notes that most origin-of-life researchers would agree that the first life developed in an oxygen-free environment, and was unable to harvest light. So they focused their analysis on anaerobic processes associated with geothermal energy. They note that, in the absence of life, geothermal processes result in a generation of concentrations of chemical energy that are difficult to convert to less-energetic forms in a reducing atmosphere. In short, the early earth would necessarily develop an energy imbalance that would be tough to get rid of. The solution? The authors propose life may have been a necessity, as it's the most efficient way of getting things back into balance.
They note that the Krebs cycle, which currently breaks down organic molecules in the presence of oxygen, would work nicely in reverse to eliminate geochemical energy by combining it with CO2. In the absence of proteins that push the Krebs cycle in a specific direction (the pre-life state), running it in reverse would also be extremely easy to do, and the reactions' cyclical nature makes for a self-sustaining system. The addition of catalysts that improve the efficiency of energy transfer would clearly be energetically favored, and the authors note that many of the intermediates in the cycle can be used in simple reactions that readily produce amino acids and sugars.
As with most origin-of-life proposals, the authors don't solve the big gap that exists between ideas regarding the origin of basic metabolism and those regarding the origin of genetic material. But they suggest that some sort of genetic material was inevitable, as a system which made the energy transfer system both sustainable and portable to other areas of imbalance would be more efficient than having to re-form one from scratch on a regular basis. They make a few other arguments from the perspective that other aspects of life, such as the formation of cells, may have also been necessitated by improvements in efficiency they bring.
They lose me when they continue the argument past the point of cellularity. At this stage, Darwinian mechanisms should kick in, and success from an evolutionary perspective can get rather far removed from efficient transfer of energy. So, for example, when they suggest that photosynthesis is little more than another form of energy transfer, I think they both understate the selective advantage of a freedom from geochemical sources and overstate the problem caused by inefficient transfer of solar energy. They also argue that the survival of some life through mass extinctions supports their view that it's energetically favorable, when it's just as likely to indicate that life exists in so many niches that it's a bit silly to contemplate wiping it all out without taking the entire planet out in the process.
Overall, however, the article is an interesting perspective on what appears to be a growing trend: the view that life is just another example of an emergent process, something that seems impossibly complex and unlikely at first glance, but actually obeys a set of simple rules that favor its formation. Like some of the other ideas regarding the origin of favorable metabolic reactions, this one should also be amenable to a certain degree of testing. Measurements of rates of reaction, energetic favorability, and tests of catalytic activity should all provide a clearer picture of how readily the Krebs cycle can be put in reverse.