Or: Complex Intelligent Lifeforms are the Inevitable Result of the Evolutionary Process Once It Has Begun
Near the southern end of the Appalachian Mountains, which extend along the eastern coast of the United States, lays the Great Smoky Mountains National Park, over 520,000 acres of land encompassing the most diversified ecology of plants and animals in North America. Over sixteen hundred species of plants, including one hundred twenty-five species of trees, along with two hundred species of birds, fifty species of fish, and sixty species of mammals are nestled into an area only a little smaller than the entire state of Rhode Island. Yet these numbers pale in comparison to the total number of species which currently exist on the planet. Some estimates approach thirty million species, ranging from ten thousand species of sponge, five thousand species of mammals, ten thousand species of birds, and twenty-three thousand species of fish, filling every possible ecological niche from the frozen arctic to equatorial Africa and down to the crushing depth a mile beneath the ocean’s surface. Life flourishes, it is indomitable, diverse, and adaptable. Yet the world’s surface could easily have been a barren landscape if not for something that happened over three billion years ago, an event which is wrongly called by some a miracle and by others a random act of chance.
On the surface, it seems that the likelihood of life formation is low, and it is tempting to narrow one's focus to argue that the probability of life forming here, on our planet, would be astronomical. Those who would argue that are entirely correct. But it is important to not lose sight of the fact that the universe is very, very large, and when one factors in all variables then the possibility of life forming in at least one place in the universe becomes a certainty.
Take the lottery for example. The odds of winning the MegaMillions lottery are 1 in 135,145,920. This means that one person buying one ticket has that much chance of winning the jackpot. So one might argue that the likelihood of someone winning the lottery have the same odds, but that would be incorrect. Each individual lottery ticket has those odds, true, but if the individual buys more than one ticket then his overall odds of winning go up. Holistically, the odds that someone will win the lottery likewise increase as more people participate. Change the variables in the equation, and the probability of success increases. And, given enough time and the same number of variables, the probability of at least one person winning the lottery becomes an inevitability. This truth is reflected in the fact that people do, indeed, win the lottery on a more or less regular basis.
This same logic can be applied to the likelihood of life appearing somewhere in the universe at least once. This is akin to the Infinite Monkeys Theory, which posits that if you had an infinite number of monkeys hitting random keys on an infinite number of typewriters, at least one of them will type out the complete works of Shakespeare. It is a probalistic certainty. Increase the number of variables within a set of parameters and the probability of a desired result becomes increasingly likely and, eventually, inevitable.
Astronomers have estimated that the universe is 150-billion light years wide. To put that in perspective, the United States is about three thousand miles wide and a jet flying at the average of six hundred miles per hour will take five hours to cross that distance. The Earth, by comparison, is ninety-three million miles from the sun, a distance 31,000 times larger, and light from the sun takes a mere eight minutes to arrive here. In one second of time, a beam of light will travel 186,282 miles, which means that if you could travel at the speed of light you could circle the entire Earth seven and a half times in that single second. A "light year" is the distance light would travel in one year's time, meaning roughly 5,878,612,843,200 miles. Multiply that number against 150-billion and you get the measure of the width of the universe.
The Earth is located within the Milky Way Galaxy, which astronomers estimate contains around 100-million stars, and our galaxy is only one of billions of galaxies. A conservative estimate of the number of stars in the whole universe exceeds 10^12 or 1,000,000,000,000,000,000,000,000. Now, if one assumes that the likelihood of finding similar conditions to those which brought about the creation of life on our world are one in one trillion, nearly seventy-four hundred times less likely than winning the lottery, then there still could be 1,000,000,000,000 Earth-like planets out there. Planets which find themselves just the right distance from just the right type of sun, covered in just the right amounts of chemicals under just the right conditions in which life could, possibly, appear. Even if one decreases the number of planets one works with, the likelihood that at least one planet in the entire universe would foment the creation of life becomes inevitable. The proof of this is the fact that we are here, we exist. Life did occur.
This should not be construed as an argument for extra-terrestrial life, however. Given a certain number of monkeys on those typewriters, the probability of one of them typing something we can read is a certainty, but the probability of more than one doing so is not guaranteed. Along the same lines, the chance of life appearing at least once in our universe, given its vast size and age, is far more probable than the likelihood that it would never occur at all. That is no guarantee that it will happen again, but neither does it preclude the possibility that it could.
The complexity of life is another matter entirely. The law of entropy says that systems trend toward dissolution, that complexity always reduces to a simpler form. Things decay, they rot, they break apart. In the world of chemistry, entropy is king. On a larger scale, however, the opposite appears to be true. A primary star composed mostly of pure hydrogen will have a short lifespan and end its existence violently. Fusion is, itself, a form of reverse entropy. While the star itself obeys the general rule and reduces to a simpler form by exploding and scattering molecules, fusion has taken those hydrogen atoms and created something more complex: helium.
Then, as the star is dying, the fusion process grasps for more fuel, and the helium becomes that fuel. Helium fuses into something more complex, and that result fuses into something more complex still. When the star becomes a nova, the material it scatters includes every element on the periodic table. We would not be here if not for the death of that star. There would be no carbon, no oxygen, no iron, nickel, silicon, aluminum, gold, nor any other element that comprises the ground we walk upon, the atmosphere that covers us, or the molecules which comprise the bodies we wear.
Likewise, life itself appears to obey a rule of reverse entropy as it becomes increasingly complex over time. Lifeforms compete for resources needed to sustain the processes of life. Better, more complex lifeforms, succeed better than simpler ones. That is evolution. While the exact processes of evolution are, as yet, unknown, the results are easily observable. What began as complex chains of hydrocarbon molecules morphed into self-replicating organisms capable of improving upon their own design. When simple evolution could not provide enough of an advantage, the organisms joined together. They learned to cooperate. Our own bodies today are amalgams of differing cells uniquely suited to performing tasks that keep the aggregate alive. Whether those cells are the descendants of different original symbiotic organisms or the result of specialization of pre-existing cells is a question for a different debate.
Putting aside the question of evolutionary mechanics, we arrive at the crux of the matter. Why should evolution culminate in sentience? Well, saying that our evolution has “culminated” would be arrogance. It is quite likely that our descendants will look back upon us in the same way we look upon Neanderthals or Australopithecines. Nonetheless, we see in ourselves something that is greater than the sum of our parts, something that sets us firmly apart from all other lifeforms. We think. We are self-aware. True, those two traits cannot be proven to belong uniquely to the human species. Chimpanzees, for instance, use tools. Language is not unique to us, either. Whales, elephants, and bees are just three of many examples of species who communicate; whales with their songs, elephants through infrasound, and bees with their dancing.
“Cogito ergo sum,” stated the French philosopher René Descartes. “I think, therefore I am.” This, at the most basic level, is the definition of sentience. We are fully aware of ourselves as entities, and that leads us to conclude that there must be something, some part of us, that transcends the flesh. Scientifically, there must be an evolutionary advantage to such a phenomenon. Certainly, our intelligence has allowed us to succeed as no other Earthly species has before. We dominate all other lifeforms on the planet, from the microscopic to the gargantuan. A virus might kill us, and we might not know the cure, but we are smart enough to learn how to avoid becoming infected. A tiger might be able to attack, kill, and devour us, but we are smart enough to band together and destroy the tiger in turn. It must be that intelligence and sentience are natural extensions of the evolutionary process. An adaptation that allowed us to not only survive but to excel. If that is so, then we must conclude that intelligence is the result of a natural process, that it is, in fact, inevitable. Just as mammals survived whatever killed off the dinosaurs, just as Staphylococcus aureus became Methicillin-resistant Staphylococcus aureus (MRSA), evolutionary adaptation transformed our earliest ancestors over the course of billions of years into us.
Again, there is no assurance that such a process is universal law. Perhaps there is a place where life formed, meaning self-replicating metabolic organisms, and where there never developed a need for ecological competition. In such a case, evolution would not have begun, and those lifeforms would remain just as they are until the condition of their environment was no longer conducive to a static existence. Why, we might ask, did evolution begin on Earth? To even begin to formulate an answer to that riddle, we must look back to the very origins of life.
In 1952, Stanley Miller and Harold Urey, two scientists at the University of Chicago, conducted an experiment in which they attempted to generate life from inorganic materials. By combining water, methane, hydrogen, and ammonia in a sealed, sterile system and applying heat and electricity, they were able to synthesize twenty-two amino acids, the building blocks of life. While they did not create life per se, it seems clear that their experiment proved that given sufficient time life, or something life-like, could arise from the primordial soup that was the very young Earth.
The Earth of 3.5 billion years ago was a very violent place. The young planet was barely a billion years old by then, only 30 million years younger than the Sun itself. Land masses and oceans had formed. The moon hung in the sky, the magnetic field had been established, and the atmosphere was charged with energy. The ocean of the distant past was nothing like it is today, not rich with mineral salts or, probably, not even quite as viscous. It was, however, thick with probiotic chemicals. It would have been a hot, energetic environment, exactly the environment that Miller and Urey recreated in their experiment. In a short time, Miller and Urey were able to create amino acids. The Earth could do it at leisure.
But what then? Amino acids, we know, combine to form proteins, but life is comprised of more than just proteins. The life we know is based upon genetics, meaning the presence of DNA or RNA. In the early 1960s, a scientist named Juan Oro conducted a follow-up experiment to the Miller-Urey research. In his experiment, he combined hydrogen cyanide and ammonia in an aqueous solution, which is theorized to also be a part of the “primordial soup.” The result was the production of adenine which is an essential amino acid for the formation of DNA. Further experiments produced thymine, guanine, cytosine, and uracil, the other amino acids needed for both DNA and RNA.
It is argued that the conditions of those experiments might not have matched the early environmental conditions of the young Earth, or that the constituent components of the “primordial soup” can not be accurately known. Taking that into account, scientists have questioned the results of both experiments. However, on September 28, 1969, a meteorite was recovered near Murchison, Australia, from which over 90 amino acids were able to be extracted. Nineteen of those amino acids are found naturally on Earth. If amino acids form so readily that even a piece of space debris contains over 90 of them, then it is not far fetched to assume that they could occur spontaneously under whatever conditions existed 3.5 billion years ago.
An alternative to the theory of abiogenesis (the theory that life arose from inanimate matter) is the theory of panspermia, the idea that life arrived on Earth pre-formed, delivered by the same kind of meteorite that fell in Australia in 1969. Such an argument sidesteps the real question, which is to ask why such life would have formed anywhere.
The oldest fossils of microbe-like objects date are 3.5 billion years old. By “microbe-like,” the reference is to organic structures called protobionts. Protobionts are simply organic compounds surrounded by a membrane-like structure which is, itself, comprised of other organic substances. While protobionts are not, technically, “alive,” they do provide an indication as to how self-replicating metabolic organisms could have arose. Abiotic replication is not a rare phenomenon, and that also gives us a clue as to how life could have formed from non-living substances.
Let’s look, for example, at a simple chemical compound such as water. Water is comprised of hydrogen and oxygen or, more specifically, one atom of oxygen and two atoms of hydrogen (hence “H2O”). Atoms are comprised of three basic components: protons, neutrons, and electrons. Protons and neutrons combine to form the atomic nucleus while electrons orbit the nucleus in complex orbits determined by natural laws. Such formations create points on the atom where other atoms are able to bind. Hydrogen has one available bond while Oxygen has two. They fit together like children’s building blocks. Likewise, complex molecules are also capable of bonding. The more complex the molecule, the more complex the bonding process becomes.
A long chain of molecules would not, for example, bond with just anything else. The analogy of children’s building blocks is apt here. Picture a complex construction of blocks, large ones and small ones, twisting and turning because the geometry of their shape dictates it. Now imagine it is floating weightless in a large room filled with other similar constructions, some of them identical but most of them not. Some constructions fit together perfectly, but only some, and the rules of connectivity are determined by the geometry of shape, which was in turn dictated by the construction of the individual components.
Now imagine that some of the constructs are broken apart or never fully formed into a whole. Those parts might fit piecemeal into place against larger, whole constructs. Additionally, other blocks floating freely, not part of a construct at all, could adhere to matching portions of the whole. In other words, a whole or a fragment of the whole would “collect” other fragments or constituent parts.
Replace the child’s constructions with structures comprised of amino acids, structures which have occurred as the result of a completely natural process. Some chains of amino acids connect together, others don’t, because of natural laws that dictate molecular structure. A complete nucleic chain which gathers fragments or constituent parts to the point that another complete nucleic chain has formed can be said to be replicating. Replication is not, however, an indicator of life. For that, replication must be combined with an ability to metabolize.
While abiotic replication might be a natural function of complex proteins, metabolism might not be. Miller and Urey theorized that the environment of 3.5 billion years ago was one rife with energy. That energy might have come from intense electrical storms, geothermic heat, or increased luminosity from a young Sun. Carl Sagan, the noted astronomer and astrophysicist, proffered the theory that cosmic radiation was the primary energy source for early metabolic processes. In other words, replication was driven by an existence within a highly energetic environment and so there was no need for proteins to generate any energy of their own. Then, as sources of external energy waned, so would abiotic replication. For replication to continue on a prolific scale, proteins would have to utilize less energy, and the easiest way to do that would be to assimilate larger fragments of matching nucleotides rather than binding amino acids one at a time.
Again, look at the analogy of the child’s toy constructs floating in space. Not all of the constructs share similar structures, either in whole or in part. However, part of one entire construct might match a portion of another. It would be much more efficient for one to take from another that portion that it would need in order to replicate. It would have to consume. And the process of consumption for the purpose of assimilating necessary molecular nutrients would be the first step toward becoming true life. As environmental energy waned, the process already underway, that of increasingly complex amino acid constructs to replicate via the consumption of raw materials, would have to be fueled by an alternative energy source. In fact, the very consumption of raw materials could provide that energy as required constituents are absorbed and nonessential molecules are cast aside. Chemical bonding and reactivity will naturally produce energy even if replication or metabolic processes are not involved. Fire is a prime example of a chemical reaction producing copious amounts of energy.
Those amino acid constructs which were able to perpetuate replication by utilizing energy released by chemical reactions were the ones which continued to “reproduce” even after there was insufficient environmental energy to sustain the process. The first instance of evolution in action. From that point on, it was competition for resources which drove evolution, pushing amino acid chains to become protobionts and subsequently change into prokaryotes (simple bacterium).
But, one might argue, what if the probability of achieving “perfect conditions” for the formation of life are much less likely than the posited one in one trillion? The answer is that requirements of meeting the definition of “perfect conditions” are much broader than one might expect. As Stanley Miller was quoted in an interview, “Just turning on the spark in a basic pre-biotic experiment will yield 11 out of 20 amino acids.” So it would seem that the emergence of self-replicating metabolic life is inescapable when conditions conducive for it to occur are present. Conditions which probability says must happen at least once. And, once life has begun, so does the evolutionary process. A process which is conducive to the advancement of increasingly complex organisms. A process in which intelligence becomes perhaps the most powerful survival trait of all. Our existence is not the result of accident or miracle, it is the inevitable result of natural processes. The physical laws that govern the behavior of subatomic particles do, in turn, govern the behavior of atoms, which dictate how molecules are able to form. Molecules that can become such things as DNA.
Much of these conclusions are based upon assumptions. It is very difficult to determine just what ingredients were in the “primordial soup.” Exactly what sparked the emergence of life, of metabolism, and what processes really drive evolution are all still merely theories. However, one inescapable fact remains: we are here. If we attempt at all to explain our existence without resorting to religion or mythology, such assumptions which best fit observable data must be made. From those assumptions, extrapolation of experimentation and theory must explain the conclusive result. When all is considered, it is not far-fetched to conclude that complex intelligent lifeforms are the inevitable result once self-replicating metabolic organisms have appeared and the evolutionary process has begun.
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