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Our future, our universe, and other weighty topics


Friday, September 19, 2014

Another Origin of Life “Progress Mirage”

The phrase “you don't know jack” is sometimes used to mean “you don't know anything.” The phrase is a shortening of a scatalogical phrase that is one word longer. It may be a slight exaggeration to say, “We don't know jack about the origin of life,” but such a statement would not not be very far from the truth.

Now some readers will no doubt think: the origin of life – didn't Darwin figure that out? No, all that Darwin said about the origin of life in The Origin of Species was this one statement: Probably all the organic beings which have ever lived on this earth have descended from some primordial form, into which life was first breathed.”

Darwin did suggest in a private letter an idea for the origin of life: “But if (and Oh! What a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity etc., present that a protein compound was chemically formed ready to undergo still more complex changes.”

But this doesn't exactly work as an explanation for life's origin. Proteins are extremely complicated molecules that are biologically assembled using the instructions stored in DNA, instructions that consist of recipes of how to assemble proteins from smaller units called amino acids. For this to work, you also need to have the genetic code, which is the “language” used by the DNA to express its instructions. Without something like DNA and something like the genetic code, there is no chance that proteins will randomly form from smaller components.

This is why the most famous experiment on the origin of life (the 1950's Miller experiment) was only a small step towards unraveling the origin of life. Miller put some gases in a glass container, and zapped the gases with electricity. Some amino acids were formed in the water at the bottom of the apparatus. It was little like producing some letters, without actually showing how the letters can form into paragraphs and books.

Miller Experiment
The Miller Experiment


In the book Quantum Aspects of Life, scientists Jim Al-Khalili and Johnjoe McFadden (a molecular geneticist) say this about the Miller experiment:

When the work was published, there was widespread anticipation that it would not be long before simple life forms were crawling out of origin of life experiments. But it did not happen. Why not? The answer is that the situation has become more complicated. For a start, the atmosphere of the early Earth is no longer thought to have been reducing. The present guess is that it was probably at best redox neutral dominated by compounds like carbon dioxide and nitrogen. Under these conditions, it is much harder to form biomolecules like amino acids. Another problem is that while amino acids were made, no proteins (polymers of amino acids) were synthesized...A fourth problem was the many essential biomolecules such as nucleic acids were not formed in the Miller-Urey experiments and have since proven to be exceedingly difficult to form in any laboratory based primordial soup experiment.

The later statement is actually an understatement, because not only have no laboratory experiments (accurately simulating early Earth conditions) produced nucleic acids (such as DNA and RNA) – such experiments have not even produced all the components of nucleic acids (only some of them).

So it seems like the famous Miller experiment was something of a “progress mirage,” a term we may use for some scientific finding that initially seems like some great leap forward, but which really doesn't move the ball very far towards the goal line. Such progress mirages are common in the history of science.

Now we may have a new example of an origin of life “progress mirage.” Some new study has been described by Scientific American with this headline: “New Steps Shown Toward Creation of Life by Electric Charge.” Wow, sounds like scientists are making progress on that “origin of life” thing, right? But maybe not, because when you read to the end of the article you get a nasty little letdown. A scientist analyzing the new study says, “‘One criticism is that the authors chose to use a somewhat reduced or hydrogen-rich mixture in their study, whereas the atmosphere on early Earth is thought to have been carbon dioxide rich, which could entail very different chemistry in the presence of an electric field.”

It sounds like the “origin of life” investigators may be up to their old tricks again. We might call it “the Miller trick.” Having trouble getting promising results using the gases believed to exist on the early Earth? Then “stack the deck” a little bit by using some different atmosphere that makes it easier to get a positive result.

Another “progress mirage,” it would seem. The unexplained origin of life billions of years ago (defying seemingly astronomical odds) remains a major thorn in the side of anyone claiming that blind chance explains our current existence. As Al-Khalili and Johnjoe McFidden put it, “The simplest self-replicating organisms alive today are far from simple and unlikely to have formed spontaneously in the primordial oceans.” While recognizing the value of Darwinian contributions, and acknowledging the reality of a very old planet, we can search for deeper principles to help explain this origin mystery.