Origin of Life Theorists Perpetuate the Implausible Miller-Urey Experiment
A ScienceNOW news release from last Thursday, October 16, states that re-analyses of the products of Stanley Miller and Harold Urey's famous origin of life experiments from the 1950s have shown that more amino acids were present than were previously thought. Origin of life theorist Robert Hazen is quoted saying the study "highlights how easy it is to make the building blocks of life in plausible prebiotic conditions."
But did the experiments use "plausible prebiotic conditions"? The news release acknowledges that ammonia and methane were "gases presumed at the time to be the main constituents of the atmosphere billions of years ago." (emphasis added) Even Miller himself admitted that he ASSUMED these atmospheres because they produced the desired result for origin of life research, NOT because of the actual physical evidence:
"It is assumed that amino acids more complex than glycene were required for the origin of life, then these results indicate a need for CH4 (methane) in the atmosphere." (Stanley Miller and Gordon Schlesinger, "Prebiotic Synthesis in Atmospheres Containing CH4, CO, and CO2," Journal of Molecular Evolution, Vol. 19:376-382 (1983).)
"We believe that there must have been a period when the earth's atmosphere was reducing, because the synthesis of compounds of biological interest takes place only under reducing conditions." (Stanley L. Miller, and Leslie E. Orgel, The Origins of Life on the Earth, pg. 33 (Prentice Hall, 1974).)
Regardless of how many chemical products useful to origin of life theorists came out of Miller's experiments, many sources have shown that the earth's early atmosphere was mainly composed largely of carbon dioxide (CO2) and nitrogen (N2), NOT methane or ammonia, as Miller's experiments required. The geochemical evidence is very clear on this point: the news release even admits, "The problem was that theoretical models and analyses of ancient rocks eventually convinced scientists that Earth's earliest atmosphere was not rich in hydrogen," and the Science paper admits, "Geoscientists today doubt that the primitive atmosphere had the highly reducing composition." Thinking along these same lines, leading origin of life theorist David Deamer observed that, "Carbon dioxide does not support the rich array of synthetic pathways leading to possible monomers, so the question arose again: what was the primary source of organic carbon compounds?" (Microbio. & Mol. Bio. Reviews, 61(2):239-261.)
A Local Volcanic Origin of Life?
The original excitement produced by the Miller-Urey experiment stemmed from the fact that it might indicate a vast primordial soup, filled with interacting organic molecules, and sufficient to overcome any great odds associated with the origin of life. After all, just last month Deamer said when asked about the "origin of the gene" that "genetic information more or less came out of nowhere by chance assemblages of short polymers." So chance still plays a big role in origin of life thinking, and one must somehow accumulate sufficient probabilistic resources to satisfy the mandates of "chance."
Since the earth's atmosphere is clearly not conducive to Miller-Urey type chemistry, the vast primordial soup hypothesis was abandoned. The ScienceNow news release suggests that instead, "It is possible that volcanoes, which were much more active early in Earth's history, seeded our planet with life's ingredients." Similarly, the paper states that "the volcanic apparatus experiment suggests that, even if the overall atmosphere was not reducing, localized prebiotic synthesis could have been effective."
But how will you get such localized highly reducing conditions in a few places on earth with a non-reducing atmosphere everywhere? In a paragraph in the Science paper describing such speculation, there is one "may" and four "coulds." Even if the "mays" and "coulds" imply a "did," such a scenario greatly reduces the amount of primordial soup to little localized pockets near island arc volcanoes, vastly reducing the ability to meet the odds required by Deamer's "chance."
I doubt that producing little localized collections of pre-biotic soup around island-arc volcanoes can produce anything remotely close to the amount of primordial soup needed to overcome the odds facing the chemical production of life. Having sufficient primordial soup to overcome the odds facing the chemical origin of life is especially important in light of the fact that origin of life scenarios still rely upon chance. But...
"The big question is what happened next"
Even if these experiments did use "plausible prebiotic conditions," they're millions of miles away from making life. Stanley Miller himself conceded in an undergraduate seminar I took from him at UCSD that "making compounds and making life are two different things." He's made statements to a similar effect publicly:
Even Miller throws up his hands at certain aspects of it. The first step, making the monomers, that's easy. We understand it pretty well. But then you have to make the first self-replicating polymers. That's very easy, he says, the sarcasm fairly dripping. Just like it's easy to make money in the stock market--all you have to do is buy low and sell high. He laughs. Nobody knows how it's done.Likewise, the news release states: "The big question is what happened next--how did those molecules turn into self-replicating organic compounds? 'That's the frontier,' [Jim] Cleaves says, 'and we're sort of stuck there.'"
(Peter Radetsky, "How Did Life Start?" Discover Magazine at http://discovermagazine.com/1992/nov/howdidlifestart153/)
Perhaps all this explains why origin of life theorists are so excited about these new reports of more amino acids from Miller's outdated and highly implausible experiment: they're a bit over-eager for some good news.