My thesis in this essay is that Darwinian evolution, succinctly summarized as “survival of the fittest,” is much more than a “theory,” the view deprecatingly offered by the Religious Right. My argument is that evolution is a natural law. First, it is a law because there are no exceptions; by definition, the survivors of any system are the elements that were the fittest. Second, it is “natural” because it is a law that applies to all mechanical and/or chemical systems. These are arrangements in which several outcomes can occur but, gradually, the “unfittest” outcomes are eliminated. The “natural law” is not restricted to living creatures.
But first, I would like to morph or evolve “survival of the fittest” into “here is a stable system.” A system that remains substantially unchanged for a reasonable period of time is a stable system. In the sense used in this essay, a stable system is one that has survived many competing forces: This is what remains after unstable configurations have been eliminated and the dust settles down.
Two examples are given below.
1) Consider the solar system. Cosmologists are far from being able to put all the pieces together, but we eventually ended up with our sun, which is an average star, surrounded by orbiting offspring. It is a stable system—stable, at least, for 10 billion years. A flock of planets orbit the sun; each planet, in turn, is orbited by moons or satellites. A tremendous number of lesser objects also orbit the sun.
Why is this system stable? Because each planet is gravitationally attracted to the sun, but this is balanced by the centrifugal force, similar to that of a weight attached by string as it swings around a central stationary point. If a planet moves closer to the sun, its speed increases, which increases the centrifugal force, pushing the planet back to its original position. If the planet moves farther away, its speed decreases, the centrifugal force decreases, and the sun pulls the planet back to its original orbit.
2) As a second example: “The Strangest Satellites in the Solar System” is the title of an article by D. Jewitt, S.S. Sheppard, and J. Kleyna in the August 2006 Scientific American. A satellite, in this case, is the moon of a planet. Most planetary moons orbit in the same direction (retrograde) as the planet’s spin– for instance, the Earth’s moon orbits in the same direction as that of the Earth’s rotation. The “strange” satellites orbit in the opposite (prograde) direction, but are in a minority. What is the reason for this? I quote the authors: “The otherwise modest effects of solar gravity accumulate over time, destabilizing the [moon’s] orbit; the ellipse elongates to such an extent that the moon either collides with the planet (or one of its larger moons) or … falls into the gravitational clutches of the sun. Prograde orbits are more vulnerable than retrograde ones. If irregular moons were originally equally likely to be either prograde or retrograde, this resonance could explain why most moons are now retrograde.” In other words, prograde moons don’t survive as well as retrograde moons; they are not as “fit.”
Continuing with the thesis that Darwinian evolution is a natural law, let’s apply it to the evolution of life. Stable systems are the foundation upon which the tree of life grows. I emphasized above that the solar system is an example of a stable configuration. A DNA molecule is, of course, stable (we are excluding, needless to say, unstable human characters). Human DNA contains billions of atoms. We can chemically, or mechanically, or electrically break a DNA molecule into millions of small molecules, each of which is stable. If we keep at it long enough, we will end up with the simplest possible group of atoms, the “organic” atoms: carbon, hydrogen, oxygen, and nitrogen (CHON), plus a small number of lesser building blocks such as sulfur and iron.
Now take all of these breakdown atomic products of a DNA molecule, place them in a glass container, and shake violently. Will the original DNA molecule eventually be reconstituted? Theoretically, the answer is “Yes,” under the proper sequence of temperature, pressure, and energy stimuli. But the chance of synthesizing aviable DNA (or RNA) molecule is extremely small. Nevertheless, this is how life began, with survival of the fittest molecules.
How can we be so sure of that? Well, in 1952, chemistry student Stanley L. Miller set up a famous experiment: He didn’t start with CHON, but with a slightly more complicated mixture of gases: methane, ammonia, hydrogen, and water (steam). As part of his Ph.D. thesis, he placed the mixture into a flask above a heater, passed the hot gases through a spark generator (to ionize the ingredients), cooled the “soup” off, and returned it to the flask, thus forming a repeating cycle. This was a hermetically sealed system. Well, after two days, the soup became a pale yellow, and Miller found that glycine, an amino acid component of DNA, had been generated. Subsequent work synthesized many more amino acids and organic compounds.
A good description of Miller’s experiment is given in J. William Schopf, Cradle of Life, Princeton Univ. Press, 1999.
The main point here is that some atoms come together to form stable molecules, and some small molecules assemble to form larger stable molecules, and so forth. This “sticking togetherness” is reserved for only a relatively few species of atoms and molecules, but the possible number of combinations is so vast that every human (except for identical twins) has his/her own unique DNA molecule. Different species, of course, are built upon different DNA molecules; these molecules are all here because they are the fittest to survive.
Another perspective is that the buildup of large molecules, in the primordial soup, followed Darwinian evolution with this difference: Small molecules come together randomly, and stick to each other if electrostatic surface fields are compatible. In everyday conventional evolution, however, organisms with different DNA, and new species, are formed via random mutation. “Survival” here means that the DNA molecule can be stable, but the plant or animal usually doesn’t survive because most mutations do not lead to a viable organism.
Next, let’s examine the origin of life as an evolutionary process:
Via gravitational attraction, the earth formed some 4550 million years ago. For 500 million years, bombardment by meteorites kept the earth too hot for living organic molecules. Then, about 4000 million years ago, in various oceans or puddles of impure water, mud, goo, or whatever, large stable organic molecules began to form. What are the chances that the first viable DNA or RNA molecules formed via this random process? Practically, but definitely not, zero. Some simple molecules can grow via polymerization, but this is a far cry from a living cell. The first living cell had to be some kind of bacteria. The first significant biological act was the formation of a membrane surrounding the DNA or RNA molecule because this is what converted, or evolved, the molecule into becoming part of a cell.
Picture large, stable molecules constantly forming in millions of cubic meters of goo over a period of 100 or 200 million years. Perhaps survival of the fittest always applied even in the primordial soup. Molecules that could replicate themselves and use energy more efficiently competed more successfully for resources. They were fitter. That’s how all those aerobic and anaerobic cycles of energy conversion and sugar formation evolved. The best enzyme for each step outcompeted other enzymes, and so forth. Some day, chemists will succeed in setting up a cubic meter of goo and, applying proper temperature, pressure, and energy source, succeed in getting a viable DNA molecule.
What happened after the first viable DNA molecule was synthesized by random accretion and grew a cell membrane around itself? Next, it imported “food” molecules from the surrounding soup. It had no enemies, no pathogens, no viruses. Eventually, as directed by its genes, it divided into two daughter cells. In a relatively short time, depending upon the external environment (food, temperature, pressure, and so forth), the first viable cell duplicated itself almost everywhere, and we had a one-species earth. The first species probably used the heat inside the earth as a source of energy.
The remainder of the story is history as we know it. Mutations gradually gave some cells an advantage in certain niches. Survival of the fittest took over.
Consider the following Evolutionary Sequence table that gives the dates when various important episodes occurred:
years since Millions of
Start of earth formed years ago
Formation of earth 0 4550
First living cells 550 4000
Single-celled algae 2550 2000
Sexual reproduction 3400 1150
Many-celled 3650 900
Trilobites 3900 650
Land plants 4100 450
Dinosaurs 4350 200
Mammals 4485 65
The table certainly contains some surprises. Life began 550 million years after the earth formed. But algae didn’t show up for 2000 million more years; Schopf has a rational explanation for the long time delay. After that, events happened faster. “Only” 850 million years for sexual reproduction between single cells. Shortly thereafter (250 million more years), single-celled plants and animals discovered the advantages of cooperative living. Trilobites, a very primitive animal, appeared 650 million years ago. Until then, life demanded a marine existence, and the land surfaces were bare. Plants finally made it to dry land some 450 million years ago. Animals, also, emerged from the sea, with dinosaurs making their debut 200 million years ago. When the dinosaurs died off, 65 million years ago, mammals took over.
Looking at the table, it is difficult to see how people of the Religious Right can insist that “evolution is only a theory.” They think it is a theory because they don’t believe that anything this complex can simply evolve. The first step is missing, the emergence of the first cell, but the science here is incomparably ahead of biblical documents that are a mixture of fact and fancy. Eventually, after reverse engineering from DNA to its constituents such as methane, ammonia, hydrogen, and water, our chemists will succeed in synthesizing the simplest of DNA or RNA molecules, and we will finally prove that goo can give birth to greenery.
Another example of evolutionary “survival of the fittest” is the sacrosanct creativity of the human mind. Peel the hype away, and what lies underneath? The nervous system of a human brain (and that of a salamander or any brain) sends electrical pulses (action potentials) along conductors (axons) from one neuron to the next. “The next” can consist of anywhere from one neuron to 100,000 neurons. The connections between one neuron and the next are “synaptic junctions”; it is here that memory is stored in the form of synaptic junction “strength,” and by the number of synaptic junctions.
Now let’s consider the creative process: You are writing a letter, say. The letter has not been memorized beforehand. Obviously, fingers move to write or type, but that is not part of creating something new. We are concerned here with the thought process. What are you thinking about in connection with that particular sentence about to be written down? For this purpose it is convenient to imagine a “consciousness platform” upon which appears 1) the visual signals (after preprocessing, with the two eye inputs merged into a single image); 2) similarly, the two auditory inputs merged into a single sound input; 3) any unusual stimulation of touch or pain from anywhere in the body; and 4) the most important part of the consciousness platform, the thought process, or what you are thinking about.
Returning to the particular sentence about to be written: Several possibilities appear, based on what has gone before, and your entire life history related to the subject at hand. This is evolution at work, again. The sentence that you select is the “survival of the fittest.” There are mutations—sentences that don’t fully make sense, and that have to be modified. But some mutations are beneficial, and may mark you as an “elegant” writer.
So the link between evolution and consciousness, in the title of this essay, takes place via the thought patterns on the consciousness platform. But this has deeper implications: A thought pattern consists of action potentials—millions of them—flying between visual input as you read the previous sentence, and memory of your past history, and the way a sentence should be constructed, and the myriad number of action potentials to the muscles of your hand, and so forth. Now imagine a robot that has exactly the same electrical equivalents of your brain: It will come up with exactly the same sentence! This is the basis for the philosophic assertion that “free will” is an illusion. All of your future actions are predetermined by the past interacting with the environment. In this sense you are a robot, fulfilling the destiny encoded in your nervous system.
Finally, there is something important to add where consciousness is concerned. One fine day in the twentieth century, say, you were born. You received the glorious, fantastic, unbelievable gift of consciousness (whatever that is). This means that, after 4550 million years of the earth’s development, you were privileged to get a ringside seat and watch the goings on for a relatively brief period of time. Much of the show is a horror story– people endlessly at war, people killing each other over the same deity, people dying in natural disasters such as earthquakes and hurricanes. But the fact that you are part of it is the most beautiful and precious gem of being alive. One can regret the many years “growing up,” and the many hours in unconscious sleep. But by all means, become an active participant; get out of your ringside seat, make believe that free will is not an illusion, and try to harness science for the betterment of mankind!