The Origin of Life: Dangers of Taking Research Claims at Face Value
Brian Miller
Brian Miller
In an article here yesterday, I wrote about philosopher Vincent Torley’s critique of my posts related to the origin of life, and I corrected his errors on thermodynamics. Today, I will correct the errors related to the state of origins research. As a general overview, origin-of-life research falls into two categories. The first is experiments that attempt to accurately model the conditions on the early Earth. The classic example is the Stanley Miller experiment which started with a combination of reducing gases (methane, ammonia, and hydrogen) that were believed to exist, and the researchers applied to the mixture electrical discharges. The resulting reactions produced several amino acids, heralded as a major breakthrough.
Unfortunately, scientists later recognized that the early atmosphere was not likely so reducing Instead, it contained a different combination of gases including carbon dioxide. All subsequent experiments conducted with more realistic starting ingredients failed to produce the building blocks of life (amino acids, carbohydrates, nucleotides, and lipids) in significant quantities. An additional challenge for all such experiments, including Miller’s, was that they produced other byproducts that would have caused deleterious cross reactions. Such conditions would have prevented any subsequent stages leading to life. All roads led to dead ends.
The consistent failure of realistic experiments led to a second class which do not attempt to model actual conditions on the early Earth. Instead, they follow what is termed prebiotic synthesis. Origins expert Robert Shapiro outlined the typical process used for RNA in his analysis of origin-of-life research. Such experiments involve a long series of highly orchestrated steps which include purifying desired products, removing unwanted byproducts, changing physical and chemical conditions, adding unrealistically high concentrations of assisting substances, and other interventions to ensure that the target molecules are achieved.
Attempting to relate such research to actual events on the early Earth leads to an almost comical series of dozens of highly improbable events. Various proposed origins scenarios over the years have involved meteorite showers, volcanos, poisonous gas, and other phenomena coupled to the precise transportation of lucky molecules through a series of multiple subsequent environments while always passing through the perfect intermediate conditions. Torley actually describes just such a fanciful scenario proposed by Sutherland. As an amusing side note, a friend reviewed origins research, and she was not sure if she was reading about scientific theories or the synopsis of the next Michael Bay natural disaster movie. Ironically, such synthesis experiments actually bolster the design argument by demonstrating that the origin of the building blocks of life and their subsequence assembly require substantial intelligent direction.
My previous article described how two of the major obstacles to the origin of life are overcoming the free energy barriers and producing the fantastically improbable configurations of atoms associated with life. The synthetic experiments bypass these challenges through intelligent intervention. As an illustration, the origin of complex molecules such as RNA and lipids must start with high free-energy solutions of reactants. However, the abundance of such sets of molecules under natural conditions drops exponentially with their free energy. Researchers overcome this challenge by starting with highly concentrated solutions of the ideal combination of pure chemicals. Highly concentrating the chemicals artificially increases their effective free energies, so reactions are driven in the desired direction.
In reality, many of the proposed starting molecules for origins theories would have quickly reacted on the early Earth with other molecules in the environment preventing substantial buildup (See The Mystery of Life’s Origins, Ch. 4). This challenge also holds true for the origination of any autocatalytic system of reactions which is another essential component for life’s origins. The dilemma is similar to that of an entrepreneur who wishes to start a business to generate a profit, but starting it requires a million dollars for an initial investment. Unfortunately, the entrepreneur is destitute and has no credit for borrowing the needed capital. As a result, he has no way to even take the first step.
The configurational challenge relates to the fact that vast numbers of chemical reactions could take place on the early Earth. However, life’s origin requires that only specific ones proceed while other far more likely ones are blocked. This hurdle relates both to the origin of the building blocks and of cellular metabolism. In addition, in large molecules the atoms can take on numerous configurations, and the right ones are exceptionally unlikely. Shapiro described how the atoms in RNA could form hundreds of thousands to millions of other stable organic molecules. Researchers overcome this challenge by forcing the atoms to achieve the desired arrangements through tightly controlling the reaction steps. Such constraining of outcomes parallels role of information in constraining messages in information theory. And, the relationship between information and precise causal control in biology was made explicit in the talk by Paul Griffiths at the Royal Society meeting on New Trends in Evolutionary Biology.
To summarize, researchers have shown how the origin of life might proceed through intelligent design, not blind processes.Shapiro illustrates this point beautifully in analyzing the experiments of John Sutherland, but his comments relate to all such experiments.
Reviewing Sutherland’s proposed route, Shapiro noted that it resembled a golfer, having played an 18 hole course, claiming that he had shown that the golf ball could have, through some combination of wind, rain, heating, cooling, dehydration, and ultraviolet irradiation played itself around the course without the golfer’s presence.
In Torley’s article he references several prebiotic synthesis experiments, but he fails to appreciate their irrelevance to the origins problem for the reasons outlined above. For instance, he describes how Sutherland and other researchers used ultraviolet light to help promote reactions leading the life. What Torley missed was that these experiments used a very specific wavelength of light (e.g., 240 nanometers) at the ideal intensity for the optimal amount of time to drive the desired reactions. If the experiments had used light mimicking that from the sun hitting the early Earth, they would have failed since other wavelengths would have destroyed the target molecules. The difference between the use of light in the experiments and the actual sun parallels the difference between the fire from a blowtorch used by a skilled craftsman and an open fire burning down a building.
Torley also describes how different researchers were able to drive key reactions even when they contained contaminants. For instance, Sutherland included a phosphate at the beginning of his experiments designed to create nucleotides. Similarly, Jack Szostak’s group created vesicles (containers) out of two fatty acids which could house an RNA enzyme (ribozyme), and he added Mg2+ which under other conditions would have prevented vesicles from forming. However, the relevance of these experiments was greatly exaggerated.
The use of such terms as “contaminant” and “messy” is highly misleading. Phosphate is an essential component of the target nucleotide molecules, and Mg2+ was essential for activating the ribozymes. They were able to include these molecules because the experiments were meticulously designed to ensure they would produce the desired outcomes. If molecules were added which would have been abundant on the early Earth (true contaminants), the experiments would have failed. As an analogy, the researchers resemble car owners boasting about how their car engines could function even in the presence of such “contaminants” as gasoline and motor oil. However, if sand and glue were added, the engines would have fared far less well.
Torley mentions one additional class of studies which use simulations to attempt to address origin-of-life challenges. Specifically, he references Nigel Goldenfeld’s research to solve the homochirality problem — many building blocks of life can come in either a right-handed or a left-handed form, but life requires only one handedness (homochiral). The results from simulation experiments are generally treated with great caution since they can be designed to model any imaginable conditions and to proceed according to any desired rules.
As a case in point, Goldenfeld’s study is based on an abstract mathematical model and numerical simulations that center on an achiral (mirror image is the same as itself) molecule interacting with the right and left-handed versions (enantiomers) of a chiral molecule to yield another copy of the latter. For instance, the “autocatalytic” reaction could start with one left-handed amino acid and end with two left-handed amino acids. The simulation set the dynamics of the reactions to eventually lead to a pure mixture of one enantiomer.
The main challenge with these results is that the underlying model is completely unrealistic. No chiral building block of life (e.g. right-handed ribose) has been shown to interact with any substance to self-replicate. On the contrary, in all realistic environments mixtures with a bias of one enantiomer tend toward mixtures of equal percentages of both left-handed and right-handed versions. Goldenfeld “solved” the homochirality problem by creating an artificial world that eliminated all real-world obstacles. All simulations that purport to be breakthroughs in origins problems follow this same pattern. Conditions are created that remove the numerous practical challenges, and the underlying models are biased toward achieving the desired results.
