Evolution - How it works
The "Watch Analogy" and What It (Unintentionally) Teaches About Evolution
Throughout this essay, we discuss misconceptions relating to evolution. Such misconceptions have had such a strong impact on modern civilization that it is important to begin by setting aside a few misguided ideas that strike at the very heart of the evolutionary process. Many of these misconceptions are embodied in a popular "argument" against evolution that goes something like this: Suppose you took a watch apart and laid the pieces on the ground. If you came back in a billion years, would you really expect the watch to have assembled itself?
This argument is a virtual museum of all the fallacies associated with evolution. First of all, a watch (or any of the other variations used in similar arguments) is mechanical, not organic or biological, which is the class of objects under discussion within the framework of evolution. In that sense, the answer to this question is easy enough: No, a watch probably never would assemble itself, because it is not made of living material and it has no need for survival.
Another problem with the watch argument is that it starts with impossibly large pieces. Let us assume that the watch is a living being; even so, one would not expect its dials and gears to assemble themselves. But evolution does not make such claims: there is nothing in the theory of evolution to lead one to believe that a collection of organs lying around on a beach eventually would piece themselves together to make a whale.
According to what paleontologists (see Paleontology) and other scientists can deduce, over the course of three billion years life-forms evolved from extremely simple self-replicating carbon-based molecules to single-cell organisms. This is hardly what one would call breakneck speed. The more visible or "exciting" part of evolution, with the proliferation of species that produced the dinosaurs and (much later) humans, took place in the past billion years. In fact, the pace of change was still very, very slow until about half a billion years ago, and it has been accelerating ever since. For the vast majority of evolutionary history, however, change has been so slow that, by contrast, watching paint dry would be like playing a high-speed video game.
Ironically, for the watch scenario to be truly analogous to anything in evolution, one would have to start with atoms and molecules not whole gears and dials. Opponents of evolutionary theory might take this fact as being favorable to their cause, but if the watch were made of living, organic material rather than metal, it is possible that the molecules would have some reason to join in the formation of organelles and, later, cells. Or perhaps they would not. Therein lies another problem with the watch analogy and, indeed, with many of the attempts to argue against evolution on a religious basis. This might be called the "fallacy of intention," or the idea that evolution is driven by some overall purpose.
THE "FALLACY OF INTENTION."
Hidden in the watch analogy is the idea of the watch itself, the finished product, as a "goal." By the same analogy, the single-cell eukaryotes of a billion or two billion years ago were forming themselves for the purpose of later becoming pine trees or raccoons or people. This is not a valid supposition, as can be illustrated by analogies to human history.
The history of human beings, of course, has taken place over a much, much shorter span than evolutionary history. (The Paleontology essay contains several comparisons between the span of human life on Earth and Earth's entire existence.) Moreover, unlike cells, people do form goals and act on intentions, so if there were any good example of change with a goal in mind, it would have to come from human beings. Yet even in the few thousand years that humans have existed in organized societies, most trends have occurred not as part of a major plan but as a means of adapting to conditions.
Consider the situation of a group of nomads who lived in what is now southern Russia about 5,000 years ago. At some point, this vast collection of tribes began to migrate outward, some moving into an area that is now central Asia and the Indian subcontinent and others migrating westward. No sane person would argue that the westward-traveling members of this group knew that in moving to the geographically advantageous territory of Europe, they were putting in place conditions that would help give their descendants dominance over most of the planet some 4,500 years later. Rather, they were probably just trying to find better land for grazing their horses.
We cannot say what the Indo-Europeans, as they are known to history, were looking for. Our only evidence that they existed is the similarities between the languages of Europe, India, and Iran, first noted by the German philologist and folklorist Jacob Grimm (1785-1863) at about the same time that Darwin was formulating his theory of evolution. Grimm, in fact, used methods not unlike those of Darwin, but instead of fossils he studied words and linguistic structures. Along the way, he found remarkable links, such as the Sanskrit word agni, cousin to the Latin term ignis and such modern English words as ignite.
In contrast to the Indo-Europeans, we know a great deal about another group of westward-moving nomads, the Huns of around A.D. 300, who were indeed looking for better grazing lands. Dislocated from their native areas by the building of China's Great Wall, the Huns crossed the Danube River, displacing the Ostrogoths. The Ostrogoths, in turn, moved westward, and this migration set in motion a domino effect that would bring an end to the Western Roman Empire in A.D. 476.
Did the Huns intend to destroy the Roman Empire and bring about the Middle Ages? No reasonable person would adopt such a conspiratorial view of history. Even more absurd, did the Chinese build the Great Wall with the idea of precipitating this entire chain of events? Again, no one would assert such a premise. If those trends in the evolution of societies were not goal-directed, why would we assume that cells and organisms would have to be striving toward a particular end to obtain certain results?
CONFUSING EVOLUTION WITH GOD.
In fact, there is no driving "purpose" to evolution—no scientifically based substitute for God operating from behind the scenes and manipulating the evolutionary process to achieve its ultimate aims. Evolution is not guided by any one large aim but by a million or a billion small aims—the need for a particular species of mollusk to survive, for instance.
As we discuss in the course of this essay, the idea of an underlying conflict between evolution and Christianity (or any other religion, for that matter) is almost entirely without merit. On the other hand, it is theoretically possible that all the processes of evolution took place without a creator—but this still should not pose a threat to anyone's idea of God.
There is nothing in evolution that would lead to the conclusion that there is no God, that the universe is not God's handiwork, or that God does not continue to engage in a personal relationship with each human. Neither is there anything in evolution that would lead to the conclusion that God does exist. Rather, the matter of God is simply not relevant to the questions addressed by evolution. In other words, evolution leaves spiritual belief where it should be (at least, according to Christianity): in the realm of individual choice.
Natural Selection
As we noted earlier, one of the principal mechanisms of evolutionary processes is natural selection. This in itself illustrates the lack of intention, or "goal orientation," in evolution. Like the name evolution itself, the term natural selection can be deceptive, implying that nature selects certain organisms to survive and condemns others to extinction. In fact, something quite different is at work.
Species tend to overproduce, meaning that the number of field mice, for instance, born in any year is so large that this entire population cannot possibly survive. The reason is that there is never enough of everything—food, water, or living space—for all members of the population to receive what they need. Therefore, only those best adapted to the environment are likely to survive.
FASTER, FURRIER MICE.
Suppose, for instance, that the climate in the area where two field mice live is very cold, and suppose that some of the field mice have more protective fur than others; obviously, they are more likely to live. If there are many speedy predators around, judging purely on the basis of that factor alone, it would be easy to predict that the swiftest of the field mice would survive. Thus, faster-running, furrier mice would be "selected" over the slower or less furry mice.
Natural selection is not simply a matter of one particular mouse surviving in an environment. Instead, it involves the survival of specific strains, or lines of descent, that are more suited to the environment in question. Individuals adapted to an environment are more likely to live and reproduce and then pass on their genes to the next generation, while those less adapted are less likely to reproduce and pass on their traits. The genetic strains that survive are not "better" than those that do not—they are only better adapted.
The process of natural selection is ongoing. For example, in generation A, the furrier field mice survive and pass on their "furriness" gene to their offspring. Some of the offspring may still not be furry, and these mice will be less likely to survive and reproduce. In addition, since there are almost always several survival factors affecting natural selection, it is likely that other traits also will determine the survivability of certain individual mice and their genes.
For instance, there may be furry but slow mice in generation B, which despite their adaptation to temperature conditions are simply not fast enough to get away from predators. Therefore, the mice in generation C are likely to be furrier and faster than their ancestors. Additional survival factors may come into the picture, to ensure that the average member of generation D has sharper teeth in addition to swifter feet and a furrier body.
Although this illustration depicts evolutionary changes as taking place over the course of four generations, they are more likely to occur over the span of 400 or 4,000 or four million generations. In addition, the process is vastly more complicated than it has been portrayed here, because numerous factors are likely to play a part. The essential mechanism outlined here, however, prevails: certain traits are "naturally selected" because individuals possessing those traits are more capable of survival.
THE "SURVIVAL OF THE FITTEST."
The concept of natural selection sometimes is rendered popularly as the "survival of the fittest." Scientists are less likely to use this phrase for several reasons, including the fact that it has been associated with distasteful social philosophies or murderous political ideologies—for example, Nazism. Additionally, the word fittest is a bit confusing, because it implies "fitness," or the quality of being physically fit.
This implication, in turn, might lead a person to believe that natural selection entails the survival of the strongest, which is not the case. Yet this is precisely what proponents of a loosely defined philosophy known as social Darwinism claimed. Popular among a wide range of groups and people in the late nineteenth and early twentieth centuries, social Darwinism could be used in the service of almost any belief. Industrialists and men of wealth asserted that those who succeeded financially did so because they were the fittest, while Marxists claimed that the working class ultimately would triumph for the same reason. Across the political spectrum, social Darwinism confused the meaning of "fittest" with that of other concepts: "strongest," "most advanced," or even "most moral." All of this, it need hardly be said, is misguided, not least because evolutionary theory has nothing to do with race, ethnicity, or social class.
In fact, "survival of the fittest," in a more accurate interpretation, means that individuals that "fit," or "fit in with," their environments are those most likely to survive. This is a far cry from any implication of strength or superiority. Imagine a group of soldiers in combat: Which type of soldier is most likely to survive? Is it the one who scores highest on physical training tests, looks the finest in a uniform, comes from a more socially upper-class home, and has the most advanced education? Or is it the one who keeps his head low, acts prudently, does not rush into dangerous situations without proper reconnaissance, and obeys instruction from qualified leaders?
Clearly, the second set of characteristics has much more to do with survival, even though these qualities may seem less "noble" than the first set. Yet it is by adapting, or proving his or her adaptability, to the environment of war that a soldier survives—not by displays of strength or other types of "fitness" that simply appear impressive. In the same way, the fitness of a species does not necessarily have anything to do with strength: after all, the lion, the "king of beasts," would die out in a polar climate or a desert or an aquatic environment.
Mutation
Although natural selection is of principal importance in evolution, mutation also plays a pivotal role. Mutation is the process whereby changes take place in the genetic blueprint for an organism as a result of alterations in the physical structure of an organism's DNA (deoxyribonucleic acid). DNA is a molecule in all cells and in many viruses that contains genetic codes for inheritance. DNA carries genetic information that is transmitted from parent to offspring; when a mutation occurs, this new genetic information—often quite different from the genetic code received by the parent from the grandparent—is passed on instead.
Under normal conditions of reproduction, a copy of the DNA from the parent is replicated and transmitted to the offspring. The DNA from the parent normally is copied exactly, but every once in a while errors arise during replication. These errors usually originate in noncoding regions of the DNA and therefore have little effect on the observable traits of the offspring. On the other hand, some mutations may be lethal, and thus the offspring does not survive for the mutation to become apparent. In a very few cases, however, offspring with a slightly modified genetic makeup manage to survive.
CONTRAST WITH ACQUIRED CHARACTERISTICS.
Mutation is not to be confused with the inheritance of acquired characteristics, a fallacious doctrine that had its adherents when Darwin was a young man. If acquired characteristics were taken to an extreme, a lumberjack who loses his arm cutting down a tree and later conceives a child with his wife would most likely father a child who is missing an arm. This notion is absurd, and attempts to put forward a workable theory of acquired characteristics in the late eighteenth and early nineteenth centuries involved much greater subtlety. Still, the idea is misguided.
The French natural philosopher Jean Baptiste de Lamarck (1744-1829), one of the leading proponents of acquired characteristics, maintained that giraffes had gained their long necks from the need to stretch and reach leaves at the top of tall trees. In other words, if a giraffe parent had to stretch its neck, a giraffe baby would be born with a stretched neck as well. Later, Darwin's natural selection provided a much more plausible explanation for how the giraffe might have acquired its long neck: assuming that the nutrients it needed were at the highest levels of the local trees, the traits of tallness, long necks, and the ability to stretch would be selected naturally among the giraffe population.
MUTATIONS AND SURVIVAL.
Unlike the idea of acquired characteristics, mutation does not entail the inheritance of anatomical traits acquired in the course of an organism's life; rather, it is changes in the DNA that are passed on. For example, when mind-altering drugs became popular among young people in the 1960s, concerns were raised that the offspring of drug takers might suffer birth defects as a result of alterations in their DNA. For the most part, this did not happen. Conditions such as Huntington disease and cystic fibrosis, however, are the result of mutations in DNA; so, too, is albinism, which eliminates skin pigment.
Although mutations often are regarded as undesirable because they can affect the health of individuals adversely, they also can have positive effects for the population in question. Suppose a group of bacteria is exposed to an antibiotic, which rapidly kills off the vast majority of the bacteria. In a fraction of those who survive, however, a mutation may develop that makes them resistant to the medication. Eventually, these mutant bacteria will reproduce, creating more mutants and in time yielding an entire population resistant to the antibiotic.
This is the reason why antibiotics can lose their effectiveness over time: bacteria with mutant genes will render every antibiotic useless eventually. The same often can happen with insect sprays, as roaches and other pests develop into mutant strains that are capable of surviving exposure to these pesticides. Such species, with their short cycles of birth, reproduction, and death, are extremely well equipped for survival as a group, which explains why many an unpleasant "bug" (whether a bacterium or an insect) has long been with us. (See Mutation for more on this subject.)
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