Remembering Stanley Miller’s 50-year-Old abiogenesis experiments on Darwin Day
A.H. Jaffor Ullah
“In this life we want nothing but facts, sir; nothing but facts.” – Charles Dickens in ‘Hard Times’
On February 12, 2009 the world is going to celebrate the bicentennial of Charles Darwin, the famous Naturalist of nineteenth century, whose seminal findings on evolution had changed the thinking of modern men when the issue is how life forms have evolved from simplest such as bacterium to complex one such as human being.
As a lifelong student of Darwin’s theory of evolution I was thinking how I should remember the life of this great discoverer on his 200th birthday. It will be redundant to enumerate the life story of this extraordinary human being. There will be other writers who would pen article to glorify his accomplishments. I however decided to discuss chemical evolution, which Darwin had no idea whatsoever.
Most biologists agree that the primitive life forms were much simpler than the ones that evolved later. Similarly, the chemicals (organic molecules) that make up simpler microorganism should also be simpler. Therefore, how these organic molecules first arose spontaneously should be a subject of interest to any students of ecology and evolution.
On October 17, 2008 New York Times ran a story on Prof. Stanley Miller’s legendary experiments that were completed about 50 years ago but this time there was a little twist to the story.
Stanley Miller who being a graduate student was a budding researcher in 1953 at the University of Chicago. His thesis advisor was Professor Harold C. Urey, a famous organic chemist at the time. Prof Urey and Miller performed experiments to probe the origin of life at chemical level. Those experiments open the mind of many researchers in the 1950s and 1960s. However, the data collected at the time was re-analyzed and these yielded new results.
It is befitting to discuss the seminal works of Miller and Urey on Darwin ’s Day celebration in 2009. Scientific truth has infinite shelf life; therefore, as long as the conclusions drawn from those experiments are still valid and irrefutable, we could discuss the findings to enrich our mind. At the heart of Miller and Urey’s experiments was this question: Could simple chemical units of life be generated spontaneously?
This year marks the 150th anniversary of the publication of Darwin ’s book “Origin of Species.” During Darwin ’s time biologists specializing on speciation and other related subjects were more interested in relatedness among species. Many of the scientists were called Naturalists. There weren’t many people interested in the chemical aspect of origin of life. That will come about 40-50 years later at the time when academic communities allover the world had already accepted Darwin ’s scientific theory of evolution.
Many Darwinists would have argued in the dawn of the twentieth century about chemical basis of life. Did those molecules that sustain life at cellular level evolved spontaneously as earth was cooling down after the “Big Bang”? Now, what were the constituents of both the primitive cells (simple prokaryotes) and modern cells (eukaryotes)? The primitive cells were more interesting to biologists, undoubtedly. Scientists in early twentieth century knew that the cell of Mycoplasma (a primitive bacterium) had primarily lipid, nucleic acids, proteins, and secondarily other metabolites. Therefore, many life scientists in 1920s and 1930s asked – could the building blocks of nucleic acid, protein, and lipid be formed spontaneously? Professor Aleksandr Oparin was the first scientist to ask this question in 1920s. To unravel this scientific problem Professor Urey directed Stanley Miller, a grad student at the time, to design a few experiments.
These earlier experiments conducted at the Chicago University are known as Miller-Urey experiments. Any good high school textbook of biology should contain the summary of these experiments. Yes, a handful of amino acids were synthesized when Miller put ammonia (a nitrogen source), methane (a carbon source), and hydrogen – all in gaseous form along with water in a sealed flask (under reducing environment) and applied electrical sparks to simulate the effect of lightning. A week later, amino acids, the building blocks of proteins, were formed out of simple gaseous molecules, which were presumed to be abundant when simple life forms were evolving. However, a few critics noted that earth’s environment was not 100% anaerobic when earliest life forms were evolving and Miller acknowledged this pitfall in his experiments. Nonetheless, Stanley Miller became quite famous for his discovery and he went on to become a professor at the University of California at San Diego after his postdoctoral stints at Columbia and Caltech. He died at the age of 77 in 2007.
After the death of Prof. Miller, Dr. Jeffrey Bada of Scripps Institution of Oceanography in San Diego, who happened to be Miller’s ex-grad student, found boxes containing hundreds of vials of dried residues collected from the experiments done during 1953-1954.
Dr. Bada carefully read the description under which Prof. Miller performed these experiments. Interestingly, two sets of experiments were carried out under varying conditions. One used a different spark generator and the other injected steam onto the sparks. The second set was thought to be interesting because Miller had replicated what might have existed in lagoons and tidal pools around volcanoes where primitive life forms may have seen first light of the day, figuratively speaking, of course!
Dr. Bada gave the task of identifying amino acids in Miller’s samples to Adam Johnson, a visiting grad student from Indiana University to his lab. In his 1953 paper Miller reported the synthesis of 5 amino acids. Samples taken from the original set of experiment had been re-analyzed by Johnson using more powerful analytical instruments available today and the result was astounding. Nine more amino acids were present in minute amounts in the original sample. When Johnson analyzed samples from the apparatus with the steam injector, he detected 22 amino acids, including 10 that had not been detected before in the original Miller-Urey experiment. This new finding was published on October 17, 2008 issue of the prestigious Science journal.
Now, what does all this means? First, nearly all amino acids were synthesized through abiogenesis. In presence of minute amounts of water vapor the spark was able to split apart water molecule resulting in a wider range of chemical reaction to take place. It is remarkable that under this condition nearly all the amino acids were formed from simple gaseous compound.
Many evolutionary biologists now think that ocean bottom is the most likely place where the building blocks came together as a living organism. Then, there are other schools of thought on how the building blocks of life came to earth. The discovery of amino acids in meteorites hinted that building blocks of life came from space. It hardly matters where the building blocks of molecule such as amino acid came from. Mother Nature had a rich inventory of molecules in the dawn of the evolution to work with and set the stage for the first life to begin.
In summary, about 150 years ago Charles Darwin published his famous book on origin of species. Since then, many scientists explained the chemical basis of life. One intriguing question was how the first set of molecules that are needed for life was created. Stanley Miller and his research advisor, Harold Urey did the first experiment in 1953 to synthesize in the lab a set of 5 amino acids. A modern method now reveals an extra set of 9 amino acids. When Miller injected steam into the reaction vessel, all 20 amino acids were made through abiogenesis. This result was published in October 2008 after re-analyzing the original sample with modern analytical instrument. This new finding goes to prove unequivocally that life could be formed from simple chemicals produced through abiogenesis. If Charles Darwin were to be alive today, he would have been very pleased with the new findings of Johnson and Dr. Bada. I think it is befitting that this new discovery came at a time when the world is celebrating the bicentennial of Darwin whose seminal work on evolution has changed the course of scientific discourse among evolutionary biologists. That is not his theory had impacted such other fields of learning as anthropology, sociology, philosophy, medicine, etc. It is only a matter of time when Darwin ’s work will be accepted universally. Let me bring the closure to this article by quoting Henry David Thoreau who wrote, “Let us not underrate the value of a fact; it will one day flower into a truth.”
Dr. A.H. Jaffor Ullah, a researcher and columnist, writes from New Orleans , USA