This is not about what is life or what is the purpose of life; as a physical scientist, I can only leave those concerns to others such as philosophers and theologians. No, this is about how life came to be. Not how life evolved over billions of years but what happened to turn inanimate chemicals in biology. This is a discussion of the chemistry to biology hypotheses, as there are a couple of them.
The universe is over thirteen billion years old, our planet about four and a half billion, and life here on earth a scant three and a half billion years. So what happened three and a half billion years ago? It depends on which hypothesis to pursue, which requires just a smidgen of consideration of what is life. I have to consider two characteristics of life, reproduction and metabolism. Life is a continuum so obviously you have to continue, but to continue you have energy ie, metabolic energy. The parts necessary for these two activities are different but somehow have to be combined.
The reproductive part of life is absolute and requires other assistive molecules to keep the process going. The most effective hypothesis so far is the “RNA” world. RNA has a structure such that it has to capacity to spontaneously reproduce itself under the right conditions. The neat thing about RNA is that it can not only act to reproduce more of itself, but also and very importantly to simultaneously do those other assistive chores. It can act as a catalyst to speed or retard chemical processes. It’s kind of a one-stop shop for biology. An RNA must spontaneously assemble as a start – no mean feat.
Likely the biggest argument against the spontaneity of life is the improbability of it happening, hence a brief diversion to probability. Take a deck of cards, shuffle, and layout one by one. What is the probability that the first card comes up to what it is? The odds are 52 to I. For the second card the odds that it is what it is, 51 to 1. For just those two cards the probability that they are there and in that order is 52 times 51, hence 2,652 to 1. Run the calculation through your layout and the odds against that happening as you laid them out is approximately 8 followed by 67 zeros to 1. Not so probable, huh? But there it is. An extremely improbable event happened right before your eyes.
Keep in mind that I am talking about the spontaneous beginning of a very simple reproducing bit of matter, much simpler than anything we can see today. I not trying to build a Ferrari here, rather design a simple pushcart, evolution will eventually get me to the race car.
In review, life may have begun with the spontaneous assembly of a primitive molecule such as RNA which has the capacity to both reproduce itself and also catalyze other processes necessary to what we call life, as improbable as that may appear.
In part II, I will explain that I was less than forthright in this first part. These things I have described as spontaneous aren’t. They go against a simple organizing principle of physical reality – entropy. Throughout the universe disorder and randomness reigns, but that doesn’t mean organization doesn’t exist, just that work has to be done to create and maintain that order. Next time, fuel for the Ferrari, stay tuned.
Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.