Andy Ellington's Citation Bluffs and the Scientific Debate Over the Miller-Urey Experiment
We've already seen University of Texas, Austin evolutionary biologist Andy Ellington's low opinion of his fellow Texans who want scientific critique of evolution taught in Texas public schools. Contra Dr. Ellington, this debate is not about "teaching intelligent design or Creationism" but whether we will teach evolution as dogmatic fact. There are legitimate scientific controversies to be taught here.
For example, in his online testimony before the Texas State Board of Education, Ellington takes issue with some of Discovery Institute's claims about the Miller-Urey experiment. He cites to his own article published by the NCSE, "Gas, Discharge, and the Discovery Institute," but he provides no details of what was allegedly wrong with Discovery Institute's arguments. Dr. Ellington mocks Discovery Institute's purported inability to respond to his arguments (his article is apparently not available online, so it's not feasible to evaluate what he said at present), but ironically we have already written a response regarding the very paper he cited before the Texas State Board of Education yesterday.
Ellington's testimony cites a 2008 paper, "A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres," co-authored by Jeffrey Bada, one of my own professors at UCSD. He claims this paper (herein referred to as Cleaves et al. (2008)) shows "significant amounts of amino acids are produced from neutral gas mixtures." However, Cleaves et al. (2008) does not show what Ellington claims it does:
(1) First, the paper contradicts pro-evolution curricula which Ellington is defending by observing that the early earth probably did not have a reducing atmosphere of methane and ammonia. (2) Second, a close analysis shows the paper doesn't actually show that amino acids can be produced under actual natural conditions on the early earth.
Regarding Point 1, Cleaves et al. (2008) notes:
Instead, evidence strongly suggested that neutral gases such as carbon dioxide, nitrogen, and water vapor--not methane, ammonia, and hydrogen--predominated in the early atmosphere.
(H. James Cleaves, John H. Chalmers. Antonio Lazcano, Stanley L. Miller, & Jeffrey L. Bada, "A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres," Origin of Life and Evolution of the Biosphere, Vol. 38:105-115 (2008).)
The paper further states that "it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N2 and CO2."
This directly contradicts a number of curricula up for adoption in Texas, such as:
Technical Lab Systems, which claims that the Miller-Urey experiments (which used methane and ammonia) used "gasses similar to the atmosphere of the early Earth." Cengage Learning, which likewise claims that "In 1953, American chemist Stanley Miller (1930-) showed in a laboratory experiment how such reactions might take place." Apex Learning, which uses a diagram showing methane and ammonia in Miller's experiments and claims, "They found that when gases that existed in the Earth's early atmosphere were subjected to continuous, high amounts of energy under certain chemical conditions, amino acids were formed." McGraw Hill (School Education Group) which also claims that the Miller-Urey experiment "simulated early Earth environments."
So unless Dr. Ellington wants Texas students learning the inaccurate claim that Stanley Miller's experiments using methane and ammonia accurately simulated early earth conditions, then perhaps he ought to point out to the Texas State Board of Education that the very paper he is citing contradicts many proposed instructional materials that have been considered for adoption in Texas. Unfortunately, Dr. Ellington didn't tell this to the board.
Regarding Point 2, Dr. Ellington fails to point out that the prebiotic synthesis experiment performed by Cleaves et al. (2008) required extensive intelligent intervention to produce these amino acids. Cleaves et al. added a buffer, oxidizing inhibitors, and acid hydrolysis "to convert any precursors to amino acids." By 'seasoning' their prebiotic soup, they intentionally created an artificially reducing environment. Thus, their simulation experiment neither documents the existence of a reducing atmosphere nor the capacity of a neutral atmosphere to generate monomers without intelligent intervention. As Stephen Meyer has pointed out, such experiments "simulate, if they simulated anything, the power of, and arguably the need for, intelligence" to move chemistry in a life-friendly direction.
Like so many other origin of life experiments, the experiments of Cleaves et al. were intelligently designed to achieve the desired outcome, such that it's difficult to argue that it represented "natural" synthesis. First, some background.
The paper explains why non-reducing neutral atmospheres don't typically yield amino acids:
The main problem in the synthesis of amino acids and other biologically relevant organic compounds with non-reducing atmospheres appears to be the limited amount of hydrogen cyanide that is formed, which is a central intermediate in the Strecker amino acid synthesis and an important precursor for the synthesis of nucleobases.
Likewise, authority James Kasting alluded to such problems when he wrote:
In the absence of a volcanic source of methane and ammonia, the post-heavy bombardment atmosphere was probably dominated by CO2 and N2 ... With regards to the origin of life, the key question is whether such an atmosphere could have generated formaldehyde (H2CO) and hydrogen cyanide (HCN). The former is needed for synthesis of sugars, the latter for synthesis of amino acids and nucleotides. ... Formation of HCN is much more difficult because it requires breaking both an N≡N and a C≡O triple bond (if one starts from N2 and CO2). Both bonds can be severed in the high temperature core of lightning discharges, but the resulting N and C atoms are more likely to combine with O atoms than with each other unless the atmospheric C:O ratio exceeds unity.
(James F. Kasting, "Earth's Early Atmosphere," Science, Vol. 259:920-926 (February 12, 1993).)
Another problem for Miller-Urey experiments is that in neutral atmospheres, products like nitrate and nitrite tend to oxidize amino acids and break them down. Cleaves et al. (2008) thus intelligently designed their experiments in two ways to effectively convert a neutral atmosphere into a reducing environment:
(1) they maintain a constant pH using a buffer system (calcium carbonate), and (2) they add oxidizing inhibitor (ascorbic acid). (They acknowledge that "[a]scorbic acid is an unlikely prebiotic anti-oxidant," so then they add ferrous iron instead.)
Thus, in a key statement, the Cleaves et al. (2008) paper exposes the tricks that were used to 'season the soup' and produce amino acids:
Buffering the reaction solution with respect to pH and the addition of oxidation inhibitors such as ascorbic acid or Fe2+ prior to hydrolysis results in the recovery of up to several hundred times more amino acids than reported previously
By adding ferrous iron, the "oxidation inhibitors" were actually reducing agents intentionally added to convert a neutral environment into a reducing one. Thus, this paper was not like Miller's original research which set up a mixture of gasses and then simply passively assessed what organic molecules were produced. This experiment did not "revisit" the Miller-Urey experiments but rather was carefully intelligently designed to convert a neutral environment into a reducing one that is favorable to producing amino acids.
The question is whether such oxidation inhibitors or pH buffers were available on the early Earth. A Ph.D. chemist (who holds a prominent research position), who is skeptical of many origin of life claims, privately critiqued the Cleaves et al. (2008) paper to me as follows:
They talk about ferrous ion as if it merely trapped unwanted competing oxidative species from destroying amino acids, etc., but given the large excesses, what they are really doing is using ferrous ion to give them a reducing chemical environment. Once this is achieved, we are back to Miller's highly reducing atmosphere scenario. While this may be reasonable from a variety of perspectives, it too begs the question: is the neutral atmosphere plus ferrous ion in the ocean a 'random condition' or a designed one? To be honest, there is no way to know for sure. At this point, the science has left the question unanswered.
The chemist continued saying that by adding all the ingredients, "They switched from passive observers to intentional controllers."
Is it appropriate to season the prebiotic soup with buffers and ferrous iron? The authors claim their position is "reasonable," but admit they don't know really the answer to that question, tentatively stating: "Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself." The authors don't know if their experiment was "natural."
There's one final artificial aspect of this experiment, as the authors note:
In our analytical procedure, the reaction mixture was acid hydrolyzed in order to convert any precursors to amino acids. Under natural oceanic conditions with the pH near neutral, hydrolysis of the precursors would likely proceed slowly, but nevertheless take place over reasonably short geologic time scales. Acid hydrolysis simply expedites this hydrolysis process in the laboratory.
Surely speeding up the reactions is necessary for practical experimental concerns, but speeding up the reactions certainly prevents many opportunities for natural conditions to break down fragile organic molecules like amino acids (which can have short half-lives). This speeding up of the reaction may provide unnatural protections to the organic products.
In closing, Ellington states:
The best source of science is scientists. If you choose to use facts, interpretations, or materials that are not validated by the scientific community, you will almost certainly find yourself in a position of trying to explain to Texas students, Texas parents, and Texas businesses why your actions have led to the willful propagation of falsehood. We cannot afford the loss of trust nor the loss of competitiveness.
Ironically, the very paper Ellington cites demonstrates that the pro-evolution teaching material submitted in Texas contain falsehoods. As for Ellington's bold claims that amino acids can be produced under neutral atmospheres, this claim is also called into question by credible scientists trained in the origin of life.
What we see evidence of here is a scientific debate over the origin of life, which is exactly what the Texas Science Standards call for when they ask students to "analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student."
By disregarding that requirement, Ellington's approach would deprive students of the very teaching methods that could solve the problems he rightly observes are facing science education today.