Stanley Miller published his original paper that isolated amino acids from an electrical discharge in one of the most widely read scientific journals called Science. It was published on May 15, 1953. What is most uncanny about this date is that another famous scientific paper was published just three weeks earlier in the other most widely read journal in the scientific community, Nature. This was Watson and Crick’s revolutionary paper that first outlined the double helix model of DNA. Since both dramatic findings were laid in the lap of the scientific community at the same time, it would be instructive to compare their respective track records of success.
The discovery of DNA’s structure set off an explosive cascade of profound scientific discoveries that have changed everything in and continue to reverberate throughout biology. In 1956, Vernon Ingram was able to identify a single nucleotide difference between a normal gene for the blood protein, hemoglobin, and the version expressed in patients with sickle cell anemia. DNA’s role in a genetic disease was thus demonstrated. In 1958, Mathew Meselson and F. W. Stahl designed an elegant experiment that showed how the DNA molecule was replicated prior to cell division (confirming the intuitive speculation that Watson and Crick raised). In the early 1960s, many scientists, including Crick, were successful in cracking the Code, determining that specific amino acids were encoded by nucleotide triplets called codons. In the late 60s, other scientists discovered special enzymes that cut DNA molecules at precise points. This paved the way for Paul Berg and colleagues who, in 1972, used these enzymes to cut DNA into pieces and then used another enzyme, DNA ligase, to paste them back together to form the world’s first recombinant DNA molecule. Genetic engineering (or gene cloning) was born. By the late 70s, Frederick Sanger, Allan Maxam, and Walter Gilbert developed different methods for determining the actual nucleotide sequence of a DNA molecule. It was now possible to determine the actual DNA ‘text’ for any gene. During the 1980s, the Biotech Era was born, as several different pharmaceutical companies began to use gene cloning to make medicines. In 1985, Kary Mullis invented a procedure called the polymerase chain reaction (PCR), a test tube method of massively amplifying DNA molecules making it possible to create genetic fingerprints commonly used in courts of law. Throughout the 1990s, an avalanche of scientific discoveries poured in helping us to better understand embryological development, disease, and evolution, all made possible by recombinant DNA technology. Scientists began to determine the entire DNA sequence of bacteria, then yeast, then worms. In 2001, both Science and Nature published the sequence of the human genome, a scientific advance that promises to change many things inside and outside of science. As a consequence, new fields of inquiry, such as genomics, proteomics, and bioinformatics have been spawned such that we have more data than can be interpreted. One cannot overestimate the importance of Watson and Crick’s discovery, as the last sixty years of biological progress, arguably the most productive span of science in human history, owes its existence to this discovery.
But what about Miller’s study? Instead of spawning its own story of vibrant scientific discoveries that have revolutionized science and our understanding of life, it’s looking more and more like another stillbirth in science that will one day be a historical footnote:
These are powerful images, so why aren’t people more excited? Echoing many sources I spoke to, Jim Kasting, who studies the evolution of Earth’s atmosphere, said, “I am underwhelmed by it.” The main problem with the study is that Miller was probably wrong about the conditions on early Earth.
By analysing ancient rocks, scientists have since found that Earth was never particularly teeming in hydrogen-rich gases like methane, hydrogen sulphide or hydrogen itself. If you repeat Miller’s experiment with a more realistic mixture – heavy in carbon dioxide and nitrogen, with just trace amounts of other gases – you’d have a hard time finding amino acids in the resulting brew.
Parker accepts the problem, but he suggests that a few specific places on the planet may have had the right conditions. Exploding volcanoes, for example, throw up masses of sulphurous compounds, as well as methane and ammonia. These gases, belched forth into lightning storms, could have produced amino acids that rained out and gathered in tidal pools. But Kasting still isn’t convinced. “Even then the reduced gases would not be as concentrated as they are in this experiment.”
Even if our young planet had the right conditions to produce amino acids, that’s a less impressive feat than it appeared in the 1950s. “Amino acids are old hat and are a million miles from life,” says Nick Lane. Indeed, as Miller’s experiments showed, it’s not difficult to create amino acids. The far bigger challenge is to create nucleic acids – the building blocks of molecules like RNA and DNA. The origin of life lies in the origin of these “replicators”, molecules that can make copies of themselves. Lane says, “Even if you can make amino acids (and nucleic acids) under soup conditions, it has little if any bearing on the origin of life.”