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Zombie Science: Miller-Urey Experiment Is Back from the Dead, Barely

David Coppedge
Image source: Illustra Media.

With the flasks, tubes, and sparks, the Miller-Urey experiment of 1953 was too good a propaganda visual to let die. This story of what biologist Jonathan Wells calls zombie science should have died the year it went viral, because Harold Urey and Stanley Miller, both well-informed biochemists, knew well that the formation of a few simple amino acids was a far, far cry from a living cell. 

They observed the tar of toxic byproducts that formed in the flask. By trapping out the products they wanted, they committed investigator interference. Scientifically speaking, the Miller experiment was a non-starter. Then later, when the atmosphere they used was called into question, the evolutionary icon was doubly dead. 

Now It’s Back

But only twitching on the table. Three geophysicists from the Technical University of Denmark, writing in Geophysical Research Letters, simulated the requirements to light sparks in the assumed prebiotic atmosphere. They used Miller’s original mixture and the revised mixture by Kasting (1993) that was more weakly reducing than Miller’s mixture of hydrogen, methane, and water vapor. The results were not encouraging. The possibility of spark generation is too doubtful to raise the Miller-Urey zombie to walking position.

In the 1950s Miller and Urey performed discharge experiments in a gas mixture resembling the atmosphere of Ancient Earth and showed that a significant amount of prebiotic material was produced, possibly laying the foundation for the further synthesis of the first biomolecules. We perform numerical computer simulations of electron avalanches in the gas mixture used by Miller and Urey as well as in a mixture suggested more recently for the composition of Ancient Earth’s atmosphere 3.8 Ga ago and study the conditions needed for the inception of filamentary discharges. We calculate electron and discharge properties and compare them with results for discharges on Modern Earth…. Our simulations show that discharges in the Miller-Urey mixture incept at lower fields than in Kasting’s mixture and partly on Modern Earth which implies that discharges in the atmosphere of Ancient Earth might have been more challenging to incept than previously thought. [Emphasis added.]

No sparks; no amino acids. No amino acids, no life. Perhaps some molecules would form from UV light or cosmic rays, but those energy sources lack the pizzazz of sparks. The textbook cartoons would be boring without those blue sparks in the flask. Everybody seems to have assumed that sparks in the flask were a good proxy for sparks in a prebiotic atmosphere. One should never assume such a key piece of the story without evidence. These authors believe it “might have been more challenging… than previously thought.”

What Did the Team Accomplish?

It’s not clear what the team accomplished if anything. They didn’t operate a Miller-type setup. They didn’t try instigating discharges in Miller’s strongly reducing atmosphere, nor in the weakly reducing atmosphere revised by Kasting in 1993 to be more plausible for the prebiotic Earth. That atmosphere eliminated the methane and hydrogen from the mix and relied primarily on nitrogen and carbon dioxide. Neither did they try getting sparks to start in a modern Earth atmosphere, although lightning is a common observation to us all. In fact, they admit that they don’t even know how lightning starts in our modern atmosphere.

Since it is known for Modern Earth that the large-scale electric fields in thunderstorms are in the order of 0.1Ek, hence seemingly too low for streamers and subsequently for lightning to occur, it is still an enigma how lightning can occur on Modern Earth (Dubinova et al., 2015; Gurevich & Karashtin, 2013). Thus, although the difference in the streamer inception electric field is rather small, it could potentially make a big difference on how efficiently streamers incept. Nonetheless, it is more difficult to incept streamers as precursors of lightning in the weakly reducing Kasting mixture than in the mixture used by Miller and Urey or in modern day air. On the contrary, in local environments, with a significant contribution of methane and ammonia, it might be easier to incept streamers, to observe discharges and maybe even create prebiotic molecules.

Might? Maybe? 

All they did was create a computer model of the requirements for streamer formation that might initiate the avalanche of electrons we call lightning. Once again, they say it was probably more challenging than thought: 

We provide a table summarizing the electric fields needed for discharge inception in these different atmospheres. Our simulations show that discharges in the Miller-Urey mixture incept at lower fields than in Kasting’s mixture and partly on Modern Earth which implies that discharges in the atmosphere of Ancient Earth might have been more challenging to incept than previously thought.

Without performing experiments, and without calibrating the conditions required for spark inception, their model is basically useless. So, what did their paper achieve? 

PR for Their Work

The only motivation that seems apparent was to get some PR for their work by tying it to the Miller-Urey experiment. In Icons of Evolution (2000), Jonathan Wells summarily executed the Miller-Urey experiment as having any relevance to the origin of life, but it didn’t stay dead. He slew it again in Zombie Science (2017). Now, again, the dead theory makes another appearance in the academic literature of the American Geophysical Union. It’s too popular to let go. Google search on “Miller-Urey” and scroll through dozens of illustrations. The focal point of them all is the spark in the flask.

Use of the wrong atmosphere is just one of an array of showstoppers that kill the Miller-Urey experiment. Others include chirality, probability, damaging cross-reactions, lack of most of the amino acid species that exist in life, and the lack of other requirements for life: a membrane, metabolism, and genetics. As if overkill were needed, this paper removes the assumption that sparks were available to get the celebrated “building blocks of life” in the first place. 

The Miller-Urey experiment is dead, dead, dead. Its promoters keep it walking with special effects, not science.

For more on problems with the Miller-Urey experiment, see also: