The Origin of Life? All in a Day's Work
Sunday, January 8, 2006
In the beginning, God created the heavens and the Earth. And He said: Let there be Chemistry.
And he looked upon the Chemistry and He saw that it was good. And then He said: Wait, we need more carbon. Also more water. Tap is fine.
Soon there was something new upon the waters of the Earth, this thing called Life. It oozed, multiplied, diversified. It learned to swim, crawl, even fly. Eventually a new form of life appeared, a creature large of brain, compulsively inquisitive, with an obsession for asking the really big, hairy, gnarly questions, such as: Where did I come from?
That's when things got really complicated.
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There is a tendency to think of science as a series of established facts and consensual theories -- "a bunch of things we know, to be memorized," in the words of Robert Hazen, the science popularizer and researcher into the origin of life.
What Hazen will tell you is that science is actually a very human enterprise. It's full of unknowns and uncertainties, of raging controversies, of passions and prejudices. Of all the great unknowns, the origin of life is particularly daunting. Direct evidence of the origin is essentially nonexistent: It happened too long ago, in too subtle a way. There's no fossil of the First Microbe. If there were, some skeptical scientist would surely raise a ruckus, saying: That's just a blob of mud.
The field has attracted people with strong personalities. They argue. They grumble. They snipe. Their debates are much more intense, and more grounded in the rules of science, than the much-hyped debate about evolution and intelligent design.
They are wrestling with basic questions: What is life, exactly? Does it always require liquid water and those long Tinkertoy carbon molecules? Does life require a cell? Did life begin with a hereditary molecule or with some kind of metabolic chemical reaction? Where did life begin on Earth? Was there a single moment that could be described as the "origin of life," or did life sort of creep into existence gradually?
All that is very much in play. In the words of George Cody, an origin-of-life researcher, "No one knows anything about the origin of life."
At the risk of absurdly oversimplifying, there are two prominent schools of thought in the origin-of-life (OOL) community: The Millerites and the ventists.
The Millerites follow in the footsteps of Stanley Miller, the mastermind of the most famous experiment in the history of the field. In 1952, working under Harold Urey at the University of Chicago, Miller created a laboratory analogue of the young Earth. One five-inch-diameter flask held water, mimicking the primordial ocean, heated by a gentle flame. A larger flask held a mixture of gases -- methane, ammonia and hydrogen -- representing a hypothetical early atmosphere. Miller zapped the atmosphere with electricity (lightning). The next day he discovered that his clear "ocean" water had turned yellow, and a brown gunk had appeared around the electrodes. The simple experiment, repeated over many days, produced organic molecules, including amino acids, some of the building blocks of life.