Thursday, February 12, 2009

The Origin of Life




Today is the 200th anniversary of Charles Darwin's birth. Fifty years later he published "On the Origin of Species by Means of Natural Selection," and the world of science has never been the same. Today also happens to be Abraham Lincoln's 200th birthday, a strange and almost awe-inspiring historical juxtaposition, but a story for another blog post.

Darwin's theory focuses on how life evolves, but not so much on how it arose in the first place. Still, his belief that the evolution of species, one into another, could be described by natural law has influenced other scientists searching for explanations for how life arose on the earth. Several ideas have been put forth involving molecules of life arising in the prebiotic soup and coming together in some way to form a living thing.

The images shown here illustrate how such a thing might have occurred. The color image is a snapshot of a chemical reaction (more on that below) which organizes itself into spiral wave patterns. The black-and-white image looks quite similar but is, remarkably, not a chemical reaction at all but a field of slime mold amoeba organizing themselves in response to a food and water shortage. The similarity of the two images has inspired a generation of scientists to determine what exactly is going on that makes these two systems produce such strikingly similar behavior.

Darwin began his university studies in medicine, following in his doctor-father's footsteps, but neglected his studies so much his father pulled him out of school and sent him off to Cambridge to study to be an Anglican clergyman. Although he was never ordained, he was much influenced in his studies by naturalists who were also theologians. Many scholars have studied Darwin's writings, trying to determine what this man really believed, but we may never fully know the truth of this. However, it is clear his scientific work was originally influenced by and, in fact, would always be intertwined with religion.

I was introduced to this subject when I was 19 years old and an undergraduate at Montana State University. I had just slipped into one of the lecture halls in the chemistry building. A slight, bearded man stood at the front of the room setting up a large flask into which he poured a clear blue liquid. As more people entered the room and took their seats I settled into a chair in the back, trying to look like I did this sort of thing every day, and watched as the man switched on the stirring mechanism. Blue liquid began to swirl in the flask.

The man, who I later learned was Richard Field, a new chemistry professor at the nearby University of Montana, began his lecture, talking about things I didn’t understand but using words which fascinated me—inorganic reactions, chemical kinetics, catalysts. I tried to concentrate on the unfamiliar topic, but my attention kept shifting to the blue liquid, swirling furiously in the tall, conical flask. I stopped listening altogether when a few streaks of red appeared in the blue. Before the red streaks had traveled even once around its perimeter, the entire contents of the flask blinked to red.

Members of the audience gasped and Dr. Field, a wiry man with twinkling eyes, stopped talking and shot a smile toward them. The red liquid, just as suddenly as it had appeared, flashed back to blue. The crowd gasped again and the bearded man smiled broadly, like a magician playing to his audience. As we watched together, amazed, the liquid in the flask began an alternating display of color: first red, then blue, then red again followed by blue – the flask oscillating between one color and the other every minute or so.

"It's called an oscillating reaction," Prof. Field explained. He had driven the distance from Missoula to Bozeman that day to meet his new colleagues at MSU. Prof. Field went on to explain that the oscillating behavior, quite unusual for chemical reactions, was an example of a larger class of behaviors called self-organization. The name, he explained, comes from the fact that the chemical reaction organizes itself into orderly patterns in either time or space—the alternating pattern of red and blue doesn’t come from anything outside the beaker, but, rather, from the interactions between the chemicals themselves. You can see a picture at the top of this post of the patterns produced when this chemical mixture is poured into a petri dish.

I was sitting in that audience listening to Prof. Field because I’d been trying to figure out what to do with my life—or, like many 19-year-olds, what my major should be —and somebody had suggested I attend the lecture to see if Chemistry might be it. I had been recruited to MSU the year before by the engineering school, offered a scholarship because (a) I had good math scores and (b) I was a girl. While it was true I was good at math, I was actually a rather unlikely prospect for science.

For one thing, very few people in my family had a college education. I grew up in Idaho in a town—Idaho Falls—that, while the second largest “city” in the state, had only about 35,000 residents at the time. Fathers of my friends were an odd combination of potato farmers and nuclear physicists due to the fact that the largest employer in town was the Atomic Energy Commission (AEC). The AEC lab, known in those parts as “the site,” holds the distinction of being the home of the world’s first ever breeder reactor, used to convert radioactive Uranium into Plutonium.

We often camped out, spreading our sleeping bags directly under the stars. Lying on my back and gazing up into the Milky Way never left me feeling insignificant and small in the face of such vastness but, rather, awed to be part of the great, wonderful mystery called the Universe. The thought of my “self” looking out through my eyes at the stars and being able to know that I was doing that always left me feeling a little bit scared; who was I, anyway, who even knew I was here? I had always had a lot of questions that half-scared, half-excited me. These moments were my first glimpse of what I would later come to think of as the Attractor in my life. They were also the first formulations of what I called my Big Question: "How is it that I know I am here?"

I am still trying to determine if this was a religious impulse or the beginning of my scientific career. Perhaps it was both.

Although I’m certain I didn’t understand this at the time, I learned later that the red/blue oscillating reaction which I had observed in Dr. Field’s lecture is a simple inorganic reaction, undistinguished in its details and very much like many other chemical reactions. One key component of the reaction—known as the Belousov-Zhabotinsky reaction after its Russian discoverers—is a catalyst molecule whose color is red in one form and blue in another. The color changes occur as the catalyst cycles between these two states, slowly converting the reactants into products in the closed flask. By the end of Dr. Field’s lecture, the near-cyclic reaction (actually more of a decreasing spiral) had run its course and the red and blue flashes that had made the flask seem almost alive had ceased. Filled with a murky purplish-colored liquid, the flask and its contents no longer looked particularly alive to any of us in the audience. In later years I would see even more experiments with this fascinating reaction, including those in which the beautiful traveling waves seen above are produced when the chemicals are simply poured into a petri dish.

But I couldn’t stop thinking about it. What made the colors change like that? Nothing I had ever seen in my growing up years—except the bubbling mud pots and geysers in nearby Yellowstone Park—could match this spectacle.

After I heard Richard Field’s talk, I attended another lecture, one of a campus series. In my quest to figure out what my major should be, I decided to go to them all. This particular lecture was given by Dr. Stanley Miller of the University of Chicago. He spoke in a packed auditorium about his now-famous experiments carried out with Dr. Harold Urey of the University of California - Berkeley. The Miller-Urey experiment attempted to reproduce conditions present on the early earth at the moment life first appeared. Miller and Urey mixed sulfuric acid with several other chemicals to simulate the early ocean—the sulfuric acid mimicked the run-off from volcanoes—and placed the mixture into a large flask pumped full of methane and carbon dioxide, the likely components of earth’s early atmosphere. Then, they shot electrical charges through the entire apparatus to mimic the action of lightning storms.

When Drs. Miller and Urey and their students inspected the contents of the flask they found, lo and behold, amino acids—molecules which, when chained together, form proteins. The electrical discharges had apparently caused the atoms in the carbon dioxide, methane and sulfuric acid molecules to rearrange themselves into new molecules, the very building blocks of life. These amino acid molecules were not alive, of course, but the fact that amino acids were formed, as opposed to, say, the building blocks of plastic, was astounding to me.

As I left the lecture hall that night, swirling in a crowd of students and professors into the cold Montana evening, under a blanket of stars that were always brilliant in that high-mountain town, my brain lit up with a thousand questions: When does a soup of molecules pass from being just a bunch of chemicals to being alive? Could a solution of amino acids keep on changing, organizing themselves—somehow—into a life form? And, if so, how in the world could they do that?

The chemicals in Miller and Urey’s flask were not alive, and neither were the ones flashing red and blue in Richard field’s demonstration of the Belousov-Zhabotinsky reaction, or BZ reaction for short—but the juxtaposition of those two lectures ignited a series of questions that I could not turn away from. Dr. Field’s explanation of the oscillating color changes as an example of self-organization intrigued me. If a simple chemical reaction could organize itself like that, what might a soup of amino acids do? Giving the mysterious process a name—self-organization—told me that these scientists, the ones who presumed they could name a phenomenon as amazing as this, might be able to guide me toward answers to the host of questions that crowded my mind after those two lectures. Maybe science held the key to finding the answers I sought.

So, here I am, decades later, still thinking about these things and delighted to be able to share a little of what I've learned in the process of finding answers to my Big Question.

2 comments:

  1. I like this, Raima! Sort of reminds me of what I like about Terry Tempest Williams' book called Refuge. The topics are way different, but it's a neat mix of personal and scientific ... or wait! E.O. Wilson's Naturalist is maybe a better example: the mind behind the science. Anyway, good stuff. Nice job!

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  2. Thank you, Anne! That means a great deal to me, coming from a great writer like you. And to be put in the company of Terry Tempest Williams and E.O. Wilson...well, gosh! I'm flattered.

    This is an excerpt from a book I am writing...working title is "God the Attractor: Spiritual Lessons from the Newest Science." Hope to start shopping it around in the next few months.

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