In the June ’07 issue of Scientific American, the article “A Simpler Origin for Life” discusses a new approach for figuring out how life could have spontaneously arisen. The views of evolutionary biologists have evolved over the last few decades from assuming that the extremely unlikely spontaneous formation of simple DNA must have occurred, to realizing that the somewhat less unlikely spontaneous formation of RNA must have preceded DNA as the origin of life. But the odds of this is still low enough to keep the Creationists happily contending that it just couldn’t have happened, even if the universe has been there for longer than 7,000 years!
Now, there is a new (competing) school of thought. What if we define life as that which metabolizes, rather than that which reproduces? Reproduction is very likely to spontaneously arise once you have steady metabolism reactions.
What is metabolism? A circular series of chemical reactions that are fed by an energy source and result in byproducts of more complex molecules. The energy source could be “burning” sulfur or oxygen, or it could be incident sunlight, or even a thermal gradient across a crystalline surface. Examples of these reactions are easy to find in nature, and are similar to those used in industrial chemistry (plastics, pharmaceuticals, etc).
A complex example would be the way that animals “burn” carbon with oxygen and end up (several steps later) with adenosine-triphosphate, one of the fuels used by muscle cells. Simpler chemical examples that might lead to amino acids are illustrated in the article.
I expect to see gleeful articles from the Creationist camp about how evolutionists are wrong, again. That they must be wrong because they again have multiple theories about which they are fiercely arguing. They must be wrong because life is certainly more than just metabolism. They must be wrong because God didn’t even mention metabolism in the KJV!
I expect eventual supremacy of this new definition, and it’s direct demonstration in the laboratory. One serendipitous development from this theory of the origin of life might be to finally settle the question about what environment first hosted life? The major contenders are: In a soup, on a wet surface, or in electrified mist. I’m betting on the surface, because an anchored molecule in a moving medium provides opportunity for fuel (hydrogen sulfide?) to enter, and for waste (RNA?) to spin off.
From space? No theory accounts for life forming in space, just traveling across from wherever it did generate.
See, I told you God wasn't real, and you didn't believe me!
"The major contenders are: In a soup, on a wet surface, or in electrified mist."
Which one of those would include the nutrient-rich "black smoker" volcanic vents at the mid-ocean-ridges? Wet chunky soup?
http://en.wikipedia.org/wiki/Black_smoker
A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of 2500 m. No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organism discovered in nature to use a light other than sunlight for the photosynthetic process (Beatty, et al., 2005).
http://en.wikipedia.org/wiki/Black_smoker
Ben: The black smoker environment is a soup: ionic liquid full of minerals and mixed molecules. It is also a wet surface interface environment. Similar environments may well be found in the oceans of Titan, or the methane seas of the gas giants.
* Education is the scientific exchange of ignorance. Leonid S. Sukhorukov
As a bit of a side note regarding photosynthesis, it might surprise some of you to know that the chemical structure of chlorophyll is very similar to the chemical structure of hemoglobin. They function very differently, of course, but they are remarkably similar in structure.