Darwin’s Warm Little Pond
You might remember from high school science class that life arose from some kind of primordial soup of inorganic chemicals. This was the twentieth century’s version of Darwin’s “warm little pond” that he wrote about to his colleague Robert Hooker.
“It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present. But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, – light, heat, electricity &c. present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter wouldd be instantly devoured, or absorbed, which would not have been the case before living creatures were formed. 1“
Keep in mind that this was written in 1871, when the science of biology, chemistry, and geology were still quite young. In this letter, Darwin is merely speculating along the lines of the common wisdom of his day. Darwin’s theory of evolution has come to be one of the most successful scientific theory we have, but that theory doesn’t address how life began, but rather how life has come to be so diverse from the first life form(s).
Haldane’s Primordial Soup and The Miller-Urey Experiment
Over the next 50 years, the speculation was refined by increasing knowledge about the age of the earth and the great changes in geologic and atmospheric conditions that took place over the millions of years. In 1952, a student of Harold Urey, Stanley Miller conducted an experiment2 wherein he tried to duplicate what was thought to be the conditions some 4 billion years ago in which life might have arisen from inorganic compounds, previously suggested by Alexander Operin and J.B. S. Haldane. This is known as the famous Miller-Urey experiment in which Stanley Miller placed some chemicals in a sealed container through which he passed electric current, hoping that organic compounds would be formed in the process.3
No Soup For You
Miller actually did manage to create some 20 organic compounds that are similar to those found in living organisms.4 So although the experiment was simple, it seemed to provide a satisfying answer that life could have emerged from some kind of primordial soup. In fact science textbooks had a section devoted to this experiment as recent as 15 years ago.
But what is published in high school science textbooks is often very far behind the state of the art. Scientists have known for many years that a simple puddle of chemicals would not be able to synthesize the more complex organic molecules that life would have required to get a jump-start. There is a thermodynamic problem in that the necessary reactions require too much energy to overcome some initial barriers for the needed chemical reactions. It is like having to push a round rock up a little hill and over the top before it can roll down a long steep slope by itself. Furthermore, the conditions found in the ancient earth are now thought to be very different from the water/methane/ammonia/hydrogen chemicals and gases used in Stanley Miller’s experiment 5
So in mainstream science the primordial soup theory along with the Miller-Urey experiments were moved to the back dusty shelf labeled, “interesting”.
So If Not Soup, Then What?
The question remains, however, that if the mechanisms that build these complex molecules are controlled by them, how did life ever begin without them. Or in other words, it seems that the chemical machinery of life is necessary to drive the chemistry of life.
For example, we have a very good understanding of how DNA drives the machinery for replicating DNA and even evolving DNA. And we understand how DNA drives the machinery for manufacturing all the other essential proteins and amino acids that operate the innards of a living cell. It would seem to be a kind of chicken or egg problem, and on the surface life seems to be “irreducibly complex” under the definition used by the Intelligent Design proponents.
The Big Questions
Some of the problems that needed to be overcome in the creation of life would be as follows:
- How To Obtain Energy? – At the very bottom of the energy chain, all of organic life that we find on Earth relies on the energy given off by the reaction of hydrogen and carbon dioxide. These two chemicals are plentiful in nature, but do not naturally react together without some help in getting over an initial barrier. If they are exposed to each other in a “soup”, they will not react on their own. So before life began, what mechanism had to come about to promote this reaction?
- Where Did DNA Come From? – In all living organisms, metabolism is controlled by the complex organic molecules that are built from instructions that originate in DNA. And DNA is one of those same kind of complex molecules. We know how organisms evolve complex systems through the evolution of their DNA, and that is no mystery to us at all. And we know how life comes from the replication of life, so why life continues is also no mystery. The question is, how did DNA arise before there was metabolism? It appears to be a kind of chicken and egg problem.
- Where Did Metabolism Come From? – And the next obvious question from the previous one is where did the metabolic processes come from before there was DNA?
- Where Did Cells Come From? – And we also observe in living organisms that life is built out of living cells, and all the machinery for life and making new life is contained in these cells. Cells are the “legos” of life. Cells are built out of complex organic compounds that are built by machinery driven by DNA, and the activity in cells are driven by the information contained in DNA and the environment in which the cell finds itself. Before DNA, and before metabolic processes, where did cells come from? More chicken and egg questions.
So it is no surprise that the primordial soup explanation has not been satisfying as a scientific explanation or even a scientific speculation for decades now. As critics of evolution sometimes point out, the probability of these things coming about by sheer random chance in a sloshing warm soup of chemicals is astronomically small (but only if you assume purely random processes, see article Hoyle’s Junkyard Fallacy). And science would further add that sheer luck is not the only problem because most of the reactions are not conducive to happening on their own anyway without some kind of mechanism present to overcome thermodynamic barriers that prevent them.
Breakthroughs in the Twenty First Century
In the last 15 years or so, a number of breakthroughs have taken place that have broken the field of abiogenesis research wide open. The breakthroughs are related to the discovery of certain deep-sea alkaline thermal vents that seem to contain all the chemistry and support all the metabolic mechanism that would be needed to jump-start organic life on Earth. So the problem of both chemistry and mechanism seem to be explainable by the conditions found in the dynamic geology of the ancient earth, the composition of its atmosphere, and the very special conditions found in the deep-sea alkaline vents. For more details see the article, The Cradle of Life: Deep-Sea Alkaline Vents.
- Letter to J. D. Hooker, 1871 ↩
- Miller, S. 1953. A production of amino acids under possible primitive earth conditions. Science 117:528–529. ↩
- Stanley Millers 70th Birthday (PDF) ↩
- http://www.sciencedaily.com/releases/2008/10/081016141411.htm ↩
- Chang, S. 1994. The planetary setting of prebiotic evolution. In S. Bengston, ed. Early Life on Earth. Nobel Symposium no. 84. Columbia University Press, New York. p.10–23. ↩