The Miller-Urey Experiment

The Origin of Life

Though Darwin’s theory of evolution applies to the diversification of biological life, not the origin of biological life, scientists have nonetheless attempted to find a naturalistic explanation of life’s origin through recourse to Darwinian type events. Competition between the first self-replicating molecules is thought to have led to increasingly efficient and complicated bio-molecules until the first primitive cell emerged. The question then is: where did these first self-replicated molecules come from? Every living thing known to science utilizes the same set of bio-molecules to reproduce: DNA, RNA, and proteins. These are enormously complicated molecules that, respectively, contain genetic information, the ability to translate and transport genetic information, and the ability to construct molecular machines (including other proteins) based on that information. Without all three components in place and functioning, there is no self-replication. The difficult task facing origin of life scientists is to discover which bio-molecule came first, and how, and then to show how the other bio-molecules developed to form the first reproducing organism.

Darwin himself thought that life may have arisen from a “warm little pond,” and in the early 20th century the scientists J.B.S. Haldane and A.I. Oparin independently speculated that a pre-biotic organic soup must have arisen early in the Earth’s history. Haldane and Oparin postulated a reducing atmosphere for the early Earth, an atmosphere containing abundant hydrogen, methane, ammonia, and water vapor. It was a logical assumption, as hydrogen is the most abundant element in the universe, and methane and ammonia are both hydrogen containing compounds. In this environment organic molecules were thought to naturally accumulate into the organic soup, and eventually, into life itself.

Miller’s Experiment

In 1953 a graduate student name Stanley Miller decided to test what may be called the “Oparin-Haldane Hypothesis.” Working under his advisor, Harold Urey, Miller created an experimental set-up to explore whether synthesis of organic molecules was possible in the hypothetical atmosphere of the early Earth.

Miller’s device (see Figure 1) contained three main compartments filled with water, methane, ammonia, and hydrogen. The water was boiled and electrical charges were sent through the vapors, which then passed into the next compartment and cooled and condensed. He ran the device for a week and then analyzed the resulting compounds. Miller discovered that among the compounds were some amino acids, the building blocks of proteins. This result sent a ripple through the scientific community. Miller had uncovered experimental evidence demonstrating the first steps of how life could have arisen purely through natural means. The experiment has become a staple in science textbooks, often accompanied by words like "the Miller-Urey experiment has shown that biological molecules can accumulate through natural means, and events like these led to the formation of life on Earth.1" But just how significant were Miller’s results?





Figure 1


First, it had been known for a century that organic compounds could be synthesized from inorganic ones, so the fact that organic materials can result from reactions with non-biological materials had already been discovered (Schopf 2002).

Second, it turns out that Miller’s experiment has several problems. One major problem with the Miller experiment is the assumption of a reducing atmosphere. Electrical sparks in an oxidizing atmosphere (like our current atmosphere) do not lead to any organic compounds. As mentioned above, the atmosphere was originally thought to be reducing (composed of hydrogen, methane, and ammonia) because of the abundance of hydrogen in the universe. The problem is that hydrogen is too light for earth's gravity to hold it, and it escapes out of our atmosphere (Brinkman 1969)(Catling et al. 2001). Geochemists and atmospheric scientists currently believe the Earth’s original atmosphere was neutral, not reducing (Miyakawa et al. 2002)(Shapiro 1986)(Schopf 2002)(Stanley 1999). The atmosphere came from the interior of the earth through volcanic outgassing. Small amounts of oxygen also had to be present due to photodissociation2, though the exact levels at which oxygen was present remain unclear (Brinkman 1969)(Stanley 1999). What is clear is that oxygen is present as far back as the rock record goes (Rosing and Frei 2003). In any case, it is now recognized that the early atmosphere was neutral and consisted of nitrogen, carbon dioxide, and water vapor with trace amounts of hydrogen, oxygen, and other gases (Schopf 2002)(Shapiro 1986)3.

In addition to hydrogen not being present except in trace amounts, the existence of methane and ammonia on the early Earth are also problematic. Since there was little oxygen on the early Earth, there was no ozone (O3) layer to absorb ultra-violet light. In addition, the younger sun would have produced ultra-violet light levels 30 times stronger than current levels (Schopf 2002)4. Methane and ammonia are both rapidly decomposed by UV rays and plausible suppliers of large amounts of these gases on the early earth do not exist. Neither could have been present on the early earth except in trace amounts (Schopf 2002)(Shapiro 1986). So, hydrogen, methane, and ammonia could at best be trace gases in the early atmosphere, but Miller's experiment postulated an atmosphere containing only them and water vapor. Clearly this is a fundamental flaw. Neutral atmospheres when sparked create only the simplest biological molecules, and this only with considerable hydrogen sources (Schopf 2002.) Since there are no plausible significant hydrogen sources for the early Earth's atmosphere, Miller’s experiment is something of a non-starter. However, there are other problems still.

Though it may seem trivial, the spark itself in Miller’s experiment is problematic, as there is no natural counterpart to the type of spark Miller used. He actually has tried simulating a lightning-type spark and, in his own words "very few organic compounds were produced and this discharge was not investigated further” (Shapiro 1986).

Miller's apparatus also contained a crucial piece: a trap which separated some of the resulting compounds, saving them from further exposure to energy. In nature, there is no such convenient trap, and the same energy that caused any molecules to bond would just as quickly (and in fact more commonly) break down those molecules. Energy is far more likely to break things down than to build them up. Effectively harnessing energy requires delicate, complicated, specific processes carried out by appropriate molecules. These processes do not occur in organic soup, and the soup would have moved toward equilibrium (the breakdown of all biological molecules is energetically favored in water) (Shapiro 1986)(Schopf 2002).
Interestingly, the specific arrangement of the device itself is in part responsible for the result of biological molecules. Miller had previously done the same experiment, with the same chemicals and spark, but with the pieces of the apparatus in a different arrangement and no biological molecules formed. The design of the apparatus favored the production of certain types of organic molecules, but in nature the process would not be so ordered (Shapiro 1986).

Ignoring all these problems, let us consider Miller's results anyway. The majority (85%) of the result can be referred to as tar, or organic goo, bearing no relevance to biological life (Shapiro 1986)(Schopf 2002). Of the approximately 50 major small organic compounds relevant to life, two were produced in Miller's experiments in a meaningful amount. These were the two simplest amino acids, glycine and alanine. There are twenty amino acids relevant to life, and though six were produced in Miller's experiment, only the aforementioned two were present in more than a miniscule amount. In addition, around half of the already small amounts of amino acids that were present are irrelevant to life due to the chirality problem (Shapiro 1986)(Schopf 2002). The chirality problem is that amino acids come in two forms, mirror images of the other. Only one type (the left-handed ones) are relevant to biology, and amino acids which spontaneously form will end being about half one type and half the other.

Miller’s results consisted of small amounts of a few of the molecules needed for life.5 The majority of a simple organism like a bacterium is composed of proteins (microscopic molecular machines), nucleic acids (DNA and RNA), polysaccharides (sugars), and lipids (fatty membranes). "None have been detected, in any amount, in a Miller-Urey experiment" (Shapiro 1986).

Conclusion

In short, even if the Miller experiment had turned out to simulate realistic conditions on the early Earth, its results are truly a most insignificant step toward figuring out how life arose. It is clear that the significance of this experiment has been grossly exaggerated. Miller himself has said as much. The severe problems with the experiment have led to interest in a variety of other ideas to explain the origin of life, including hydrothermal vents, meteorite seeding, and even panspermia (the idea that extraterrestrials planted the first life forms here).
So then, students should be taught that the Miller experiment is what it appears to be: a historically important but outdated and flawed experiment.

A further note: even if Miller’s experiment had generated every last biological molecule known to man, present in exactly the right proportions, we still would not have solved the origin of life. One could have all the right pieces together, in any conditions, and still “life” would not emerge. Scientists are unable to re-create any kind of cell even with all the right materials and controlled conditions. How then did it happen by accident on the early Earth?








1. Some modern textbooks do acknowledge the deficiencies in Miller’s experiments, but the Miller experiment remains an icon of pre-biotic evolution.
2. Photodissociation is the breakdown of H2O into hydrogen and oxygen by sunlight.
3. Scientists estimate that oxygen levels just 1% of current levels would prevent organic molecules from forming at all on the early earth.
4. The strong UV rays would have also instantly destroyed any biological molecules that had formed.
5. Subsequent Miller-type experiments have resulted in the production of almost all of the 20 amino acids found in proteins. While interesting, see the rest of this essay.



Works Cited

Brinkman, R.T., 1969, The photodissociation of water vapor, evolution of oxygen and escape of hydrogen in the earth’s atmosphere. PhD. Diss., California Institute of Technology, http://resolver.caltech.edu/CaltechETD:etd-10062004-120013

Catling et al., 2001, Biogenic Methane, Hydrogen Escape, and the Irreversible Oxidation of the Early Earth. Science, 839-843

Miyakawa et al. 2002. Prebiotic synthesis from CO atmospheres: implications for the origin of life. PNAS, 14628-14631

Rosing, M.T. and Frei, R., 2003. U-rich Archaean sea-floor sediments from Greenland – indications of > 3700 Ma oxygenic photosynthesis. Earth and Planetary Science Letters, 237-244.

Schopf, W., ed. 2002. Life’s Origin: the beginnings of biological evolution, California, UCAL Press

Shapiro, R. 1986. Origins: a skeptic’s guide to the creation of life on earth, New York, Simon & Schuster Inc.

Stanley, S. 1999. Earth System History, New York, W.H. Freedman and Company

My Job

I am a manager, administrator, secretary, and accountant.

I am an evaluator, psychologist, counselor, and diplomat.

I am a scholar, scientist, historian, and student.

I am a teacher, and I don't get paid enough for this job.

The Omnivore's Dilemma

I'm almost through the audiobook version of The Omnivore's Dilemma, and it's one of the most interesting books I've read in a while. If you eat food (and I'm pretty sure you do) you must read this book.

The Problem of Evil Solved

Hey, if Daniel Dennett can write a book called Consciousness Explained (though it does nothing of the sort) why can't I pretend to have solved the problem of evil? The intent of this post is not, of course, to actually solve the problem once and for all, but to demonstrate that the argument is less weighty than its proponents might think.

The standard formulation of the argument goes something like this: if God is good and all-powerful then evil should not exist. If evil exists, then either God does not exist or God is not like the traditional Judaeo-Christian view of him (i.e. either not all good or not omnipotent). It is usually taken as a given that evil does in fact exist and that this is a problem for the Christian God.

I admit that the problem is difficult from both an intellectual and an emotional viewpoint. Examples of evil (or suffering, as some philosophers might prefer) are easy to call to mind. The atrocities of the Nazi concentration camps, the victims of the tsunami of 2004, or the children from around the world who are abused each day are only a few of the examples one can provide. How could a loving, good, all-powerful God allow such things? It is a difficult question, but I think a few considerations significantly soften the force of the argument.

In the Christian worldview, God created the universe and then life to occupy it. Because God desired a rational companion he created humans. He created them in his image, and he created them male and female. Humans are unique among the animals, being the only ones able to think abstractly, use language, and act rationally. By granting humans agency, or free will, God was able to have a relationship with them. Now, God, or humans, can have relationships with dogs, cats, pigs, or whatever. Clearly, though, the relationship is very different than one that is between two agents. That is, between two beings able to choose among different actions, a relationship acquires meaning. The reason why your relationship with your mother, spouse, or brother is meaningful is because both parties have a choice in the matter. Having someone love you is meaningful only if they have the option to not love you. God then, was taking a risk when he created human agents. Apparently he thought it worth the risk to have the possibility of meaningful, reciprocal relationships. So then, the possibility of love entails the possibility of hate. The possibility of performing acts of love and grace towards others entails the possibility of performing acts of hatred.

One might respond that, yes, in general God has reasons for allowing free will, but what about those concentration camps, did God really have to allow that? This seems reasonable at first glance, but consider: where exactly should God draw that line? When someone wants to kill 100 people, should God step in and stop him? What about 10 people? How about just one? Killing one person is evil, just as killing a thousand is. A husband striking his wife is also evil. A child who is bullied at school can be damaged physically and emotionally. Should God step in each time a bully is about to act? How about the next time you are about to lie to your spouse about something? Or spend an extra hundred dollars on a new TV while children starve to death in another country? I suggest that if we head down this path, soon we will find ourselves unable to hate, dislike, steal, lie, or in short, do anything short of perfect acts. We would find ourselves automatons, blindly, unthinkingly acting “good.” But these acts would be meaningless, as we would not have any other choice. This is exactly what God did not want.

In the movie, The Truman Show, Jim Carrey plays a character named Truman who has unwittingly become the star of a TV show. The TV show simply follows his every day life, but Truman has no idea he is being filmed. He also has no idea that his entire life, from his birth up to his present day, has been staged. Everyone he thinks he knows are just actors. The town he lives in has been created solely for the purpose of the show. Truman's life is very "nice." He has friends, a wife, a steady job. The problem? Since his whole life is an artificial construct Truman eventually begins to suspect something is up; something doesn’t feel right. His life, though encountering little direct evil or suffering, lacks meaning and Truman can feel it. A universe where God orchestrated what we are and are not allowed to do would be similar. Without the risk of evil, we cannot have the possibility of true goodness and beauty.

What about natural disasters, then? Free will may explain why humans are allowed to cause other humans suffering, but why would God allow earthquakes to kill? First, I think that the natural disaster problem of suffering is much less powerful than the original argument. When I am distraught about the evil in the world, it is not usually the hurricanes and earthquakes I am worried about. That said, it is still a challenge for a Christian to answer, as obviously free will has nothing to do with natural disasters.

As someone who studies and teaches the earth sciences, I am quite familiar with natural disasters of all kinds. Interestingly, all major natural disasters have their roots in processes that contribute to the overall habitability of planet Earth. The molten core of Earth, for example, drives plate tectonics and generates the Earth’s magnetic field. Without the magnetic field, life could not survive on Earth’s surface due to intense solar wind (charged particles from the sun). Plate tectonics, among other things, creates livable surfaces above water (continents), replenishes nutrients to the Earth’s surface (through volcanic eruptions), and helps regulate global climate. Side effects of plate tectonics (a result of the molten core) include earthquakes and volcanic eruptions. These events can pose hazards for life on Earth. But without them Earth would probably not be habitable at all. Hurricanes are essentially release valves for the global climate system, distributing heat and moisture away from the equator to the rest of the world.

But couldn’t God have designed a habitable world without all of these dangerous side effects? I don’t know. But just the fact that they do play an important role weakens the force of the argument. A completely useless catastrophic occurrence would be a more difficult problem.

So where does this leave us? I don’t think the argument succeeds in showing that the Christian God cannot co-exist with evil, as God may have good reasons for allowing evil to exist. Natural disasters can still be difficult to accept, but there is at least a good reason for them to exist as well. I’m sure these answers won’t satisfy everyone, but I like to think it’s a start. I hope to read more contemporary philosophers’ take on this problem at some point (it’s been a few years). Comments?

Karate and Friendship

Apparently you need to practice something for at least 10,000 hours to master it. Also, we are all made of corn.

The Da Vinci Code

I just watched the last part of the movie The Da Vinci Code on TV. I watched it in the theater back when it first came out to see what all the fuss was about. It was OK as a movie: not terrible, not great. As history, though, it's kind of silly. I really can't believe that people take this book so seriously. Christians often get criticized for having "faith" in ancient texts, which may or may not be true or accurate. But a novel from some guy in New Hampshire happens to contain all these previously unknown secrets of history? Is this plausible?

There is no evidence that Jesus had an intimate relationship (nevermind children) with Mary Magdalene. I heard an interview with a scholar on NPR back when the movie was first out, and he discussed the texts which people suggest describes Jesus and Mary kissing, an indication of a physical relationship. The problem is that the texts are incomplete: many or most of the words are actually not there. The scholar quoted the sections in question. It was something like: ...and they were on their way..........from.......over to...........Galilee......Jesus.......lunch.....walking near the.....and then........Mary.......Jerusalem.....in between the........kissed.....returned from...etc etc. I'm obviously being facetious here, but it was something like that. The speculative leap from text like that to Jesus and Mary were lovers and had children is so large that, again, I find it hard to believe that people take this stuff seriously. The scholar said that there is no textual evidence for this stuff; people routinely kissed as a greeting back then, and Jesus and Mary were not the only ones mentioned in the text.

The assertion that Mary was in Da Vinci's painting of The Last Supper is also problematic. The painting is of Jesus and his disciples. There were twelve of them. If Mary is in there, John, a disciple, is not. I'm no art historian, but don't you think someone would have noticed if a disciple was missing before now? John, the disciple that is claimed to actually be Mary, is portrayed as feminine, and this is supposed to be evidence that it is a female. The problem: the character is wearing male clothing and it was not uncommon at the time (or in other works of Leonardo) for a subservient male to be portrayed as feminine. John's femininity is suppose to imply his lower status (compared to Jesus)and love for Jesus. The evidence for Mary being in the painting is therefore thin. Besides, are we really supposed to believe that Dan Brown (or the book he got this idea from, Holy Blood, Holy Grail) uncovered this secret that scholars have missed for the last 500 years?

Among other things, the movie stated that Newton was persecuted by the church. This is completely false. Newton was the leading man of one of the most conservative universities. He was a firm believer in God and believed his scientific work was uncovering the secrets God had used to create the universe. He also wrote extensively on theological matters (more than he did on science, actually).

The movie also laughably stated something along the lines of...did you ever wonder why the most talked about object in Christianity, the holy grail, is missing from Da Vinci's painting? The "holy grail" is never mentioned in the Bible, and I have never heard any Christian talk about it. It was probably an invention of some church in the Middle Ages who wanted a relic to draw pilgrims.

Anyway, if nothing else, The Da Vinci Code is an interesting example of peoples' propensity to believe nonsense as long as it somehow challenges orthodox views within Christianity.

Warm hands make you nice?

In a study from Yale University, researchers found that people who held something warm in their hands were nicer towards others than those who held something cold. The lead researcher says that subtle clues from our environment can impact our psychological disposition; warm hands help you have a "warm" heart. But...this study seems to overlook something. Something icy in your hand is uncomfortable; something warm is close to your natural body temperature and is therefore more "normal" than warm. It seems to me that merely the discomfort caused by the chill in your hand probably explains why people might be more irritable towards others, not some connection between physical warmth and psychological "warmth." In order to show that, people would need to hold something uncomfortably hot in their hands and still have the same friendliness towards others. If the comfort level is different between the two groups, then we don't know if it's really the temperature that makes the difference or the discomfort that makes the difference. Since more than one variable is involved, the results of the study are suspect. Thoughts?