2006 : WHAT IS YOUR DANGEROUS IDEA?

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Professor Emeritus of Chemistry and Senior Research Scientist, New York University; Author, Planetary Dreams
We shall understand the origin of life within the next 5 years

Two very different groups will find this development dangerous, and for different reasons, but this outcome is best explained at the end of my discussion.

Just over a half century ago, in the spring of 1953, a famous experiment brought enthusiasm and renewed interest to this field. Stanley Miller, mentored by Harold Urey, demonstrated that a mixture of small organic molecules (monomers) could readily be prepared by exposing a mixture of simple gases to an electrical spark. Similar mixtures were found in meteorites, which suggested that organic monomers may be widely distributed in the universe. If the ingredients of life could be made so readily, then why could they not just as easily assort themselves to form cells?

In that same spring, however, another famous paper was published by James Watson and Francis Crick. They demonstrated that the heredity of living organisms was stored in a very large large molecule called DNA. DNA is a polymer, a substance made by stringing many smaller units together, as links are joined to form a long chain.

The clear connection between the structure of DNA and its biological function, and the geometrical beauty of the DNA double helix led many scientists to consider it to be the essence of life itself. One flaw remained, however, to spoil this picture. DNA could store information, but it could not reproduce itself without the assistance of proteins, a different type of polymer. Proteins are also adept at increasing the rate of (catalyzing) many other chemical reactions that are considered necessary for life. The origin of life field became mired in the "chicken-or-the egg" question. Which came first: DNA or proteins? An apparent answer emerged when it was found that another polymer, RNA (a cousin of DNA) could manage both heredity and catalysis. In 1986, Walter Gilbert proposed that life began with an "RNA World." Life started when an RNA molecule that could copy itself was formed, by chance, in a pool of its own building blocks.

Unfortunately, a half century of chemical experiments have demonstrated that nature has no inclination to prepare RNA, or even the building blocks (nucleotides) that must be linked together to form RNA. Nucleotides are not formed in Miller-type spark discharges, nor are they found in meteorites. Skilled chemists have prepared nucleotides in well-equipped laboratories, and linked them to form RNA, but neither chemists nor laboratories were present when life began on the early Earth. The Watson-Crick theory sparked a revolution in molecular biology, but it left the origin-of-life question at an impasse.

Fortunately, an alternative solution to this dilemma has gradually emerged: neither DNA nor RNA nor protein were necessary for the origin of life. Large molecules dominate the processes of life today, but they were not needed to get it started. Monomers themselves have the ability to support heredity and catalysis. The key requirement is that a suitable energy source be available to assist them in the processes of self-organization. A demonstration of the principle involved in the origin of life would require only that a suitable monomer mixture be exposed to an appropriate energy source in a simple apparatus. We could then observe the very first steps in evolution.

Some mixtures will work, but many others will fail, for technical reasons. Some dedicated effort will be needed in the laboratory to prove this point. Why have I specified five years for this discovery? The unproductive polymer-based paradigm is far from dead, and continues to consume the efforts of the majority of workers in the field. A few years will be needed to entice some of them to explore the other solution. I estimate that several years more (the time for a PhD thesis) might be required to identify a suitable monomer-energy combination, and perform a convincing demonstration.

Who would be disturbed if such efforts should succeed? Many scientists have been attracted by the RNA World theory because of its elegance and simplicity. Some of them have devoted decades of their career in efforts to prove it. They would not be pleased if Freeman Dyson's description proved to be correct: "life began with little bags, the precursors of cells, enclosing small volumes of dirty water containing miscellaneous garbage."

A very different group would find this development as dangerous as the theory of evolution. Those who advocate creationism and intelligent design would feel that another pillar of their belief system was under attack. They have understood the flaws in the RNA World theory, and used them to support their supernatural explanation for life's origin. A successful scientific theory in this area would leave one less task less for God to accomplish: the origin of life would be a natural (and perhaps frequent) result of the physical laws that govern this universe. This latter thought falls directly in line with the idea of Cosmic Evolution, which asserts that events since the Big Bang have moved almost inevitably in the direction of life. No miracle or immense stroke of luck was needed to get it started. If this should be the case, then we should expect to be successful when we search for life beyond this planet. We are not the only life that inhabits this universe.