Undoubtedly, the Theory of Evolution as put forth by Charles Darwin has had a profound effect upon the world as it stands today. From molecular genetics to religion, Evolution has turned the way humans think and approach the world on its head. Unfortunately, this theory is widely misunderstood and its principles are often improperly and erroneously applied. This misunderstanding flows from the seemingly ubiquitous nature of humans to personify inanimate nouns and proffer human emotion, reason, and sentiment to strictly physical phenomena.
Granting human qualities to physical phenomena is a relatively efficient means of making practical decisions as it provides a familiar “working model” with which to weigh choices. Nevertheless, personifying physical phenomena is wrought with disaster when attempting to apply scientific reason. Indeed, it is only through suspending this behavior, a task of momentous self-discipline, that scientific theories are advanced and the true state of the natural world can be investigated. The practice of suspending such convenient human behavior is made all the more difficult by an imprecise language that lacks the means of expressing scientific findings in a descriptive manner that does not invoke strictly human qualities. Humans are an egocentric bunch and as such our method of communication has evolved to describe the world as it relates to us and not to accurately portray abstract theories and complex physical processes.
A scientific theory is defined by Dictionary.com/Unabridged (Based on the Random House Dictionary, 2006) as a coherent group of general propositions used as principles of explanation for a class of phenomena. This is in contrast to the lay use of the term theory in which it means a guess or conjecture as opposed to facts. In science, a theory is a well-tested, long-standing group of principles used to explain a natural occurrence without invoking any supernatural agent. In other words, it is a model for understanding the world that has a great deal of evidence in support of it, but which is being tested continually. As such, the Theory of Evolution is simply a set of principles that allow humans to understand how living creatures grow, change, and adapt in response to the environment they find themselves in. It consists of several notions, including natural selection, random drift, inheritance, and so on and so forth. This is where we begin our discussion of what evolution is as well as what evolution is not.
Evolution, simply put, is change. Many things evolve, including technology, societal norms, religion, automobile design, and on and on and on. Darwin’s Theory of Evolution is a tool for understanding how change takes place in the special case of living organisms. Evolution is not the notion that humans came from apes, as is popularly believed, but rather the Theory of Evolution describes how and why living organisms change. In an esoteric sense it is a method of understanding how the diversity of life came to be. In more practical terms, it allows scientists to understand how bacteria change in response to antibiotics, how the HIV virus changes and evades treatment, and how selective breeding influences livestock traits, just to name a few. Evolution is a fact in that living organisms change over time. The theory of evolution is the model for understanding how the change takes place. The theory of evolution could be renamed the explanation of evolution. In other words, Darwin’s theory was put forth in order to explain, without invoking the supernatural, how the variety of living organisms that can be observed came to exist. That organisms change and adapt is not a theory, but is a fact. The method by which change in living organisms takes place is what the theory addresses.
Darwin’s book was entitled On the Origin of Species by Means of Natural Selection and the theory that it put forth was monumental. It stated that speciation (i.e. the development of distinct and separate classes of organisms) was a result of survival of those individual organisms best suited to endure the prevailing environmental pressures. In other words, the better suited a given individual was to negotiating its current environment the more likely it was to survive. By surviving, that individual was more likely to reproduce and thus its particular traits were more likely to be passed to the next generation. Over long periods of time, this led to certain traits being favored over others.
Darwin made his observation while visiting remote and exotic places during a five-year-long sea voyage. He observed that the animals on islands and in other remote locations were somewhat different from their cousins on the mainland. Though similarities could be seen, what stood out were the differences. The animals on the islands were uniquely adapted to survival on those islands. This suggested was when a group of organisms was divided into two or more groups by some geological process (an island, an insurmountable mountain range, etc.), that the differences in environmental pressures eventually led to the development of different species.
The key, Darwin surmised, was reproduction. When the group was divided, each faced separate conditions necessary for survival. An example can help to explain this. There will be one group of turtles we will call A. The turtles in group A all have the same quality whereby they have feet adapted for walking slowly on fairly level ground where there is little water and few predators. At some point in time, this group of turtles is separated when an earthquake results in an insurmountable cliff developing. On the top of the cliff there is now one group of turtles, group B, and at the bottom of the cliff is another group, group c. Because the cliff is present, group B is effectively separated from group C and no interbreeding can take place. On top of the cliff now, the environment is different from that below the cliff. On top, the ground has become uneven and a new predator has arrived that finds turtles a tasty morsel. The turtles of group B now face a new challenge, the predator. The individuals in group B all have slightly different abilities when it comes to climbing trees. Some are great climbers, some modest, and some cannot climb at all. Those that are the best climbers have bigger claws, which allow them to grip the trees more effectively. Due to their ability to climb, these turtles are able to avoid being eaten better than the poor climbers and thus live long enough to have baby turtles. These baby turtles will be equipped with the climbing abilities of their parents and, as time progresses, group B changes from predominately land-dwelling to predominately tree-dwelling. As this occurs, they also adapt to new food sources, different methods of reproduction, and a whole host of other things. Group B is now species B and arose from species A.
While group B is undergoing its changes, group C, below the cliff is also facing new challenges. There is more water than there once was and the food sources tend to be aquatic and not land based below the cliff. In group C, the same spectrum is found. Some turtles are great good swimmers, some are moderate, and some cannot swim well at all. Those that swim the best will be able to reach the food sources easier and thus are more likely to live long enough to have baby turtles. The babies will have the trait of improved swimming and over time will adapt to a more aquatic environment. They also will undergo changes in response to their new environment, developing new reproductive and feeding habits and eventually becoming species C.
What makes two groups different species is that ability to breed. Once the two cannot interbreed, even if placed together again, they are effectively two separate species. They shared the same origins, species A, but are now two distinct species, B and C. Species A was the ancestor to both B and C, but A no longer exists because the environment changed and the conditions no longer favored the survival of species A. In effect, species A is extinct. It is extinct not due to a meteor or volcano that killed them all, but instead as a result of slow adaptation. This concept is referred to as survival of the fittest and formed the basis of Darwin’s theory. Basically, selective breeding among the fittest of individuals resulted in different species arising.
In order to understand how one individual gains an advantage over another, it is important to discuss the concept of mutation. This is where many people get hung up on the theory of evolution as they have often been given conflicting and inappropriate information regarding how living things change over time. First, a discussion of the common, though incorrect, version of how organisms change.
A theory was originally put forth by a man named Lamarck suggesting that individuals were able to slowly adapt their own bodies over the course of a life time in order to meet challenges in their environment. His famous example was the giraffe. He thought that the giraffe developed a long neck by stretching to reach the leaves in tress over the course of its life. Then, that long neck could be passed on to the next generation. This of course, was false. We know that a single individual cannot drastically change its own physique during its lifetime. A neck will stay the same length over time no matter how much one tries to stretch it. How then did the giraffe’s long neck come to be?
The answer is mutation and what makes it hard to comprehend is that it is random. The truth is that DNA is the blueprint for life. Encoded with this molecule is all the information that is needed to create a given organism. In the case of the turtles, their DNA carries all the information that is necessary to make them turtles. When a turtle has a baby turtle, it makes a copy of its DNA and passes some it on to that baby. Now, the problem with DNA is that it does not always copy itself accurately. This means the DNA the parent turtle passes on to the baby may have some copying errors in it. These copying errors are referred to as mutations and come in three flavors: good, neutral, and bad.
Good mutations are those changes in the DNA that result in a change in the organism that gives it a survival advantage. In the case of our turtles from group C, this could be a change that allows webbing to grow in their feet, which translates to better swimming ability. Note that while this change is advantageous to the turtle in group C, it could be neutral or bad for the turtle in group B. In other words, the utility of a mutation is determined by the environment the individual is in at the time the mutation occurs.
Neutral mutations produce no harm and provide no benefit. These mutations occur because, though the DNA changes, the mutation is not in a critical region, does not affect the final product substantially, or provides a change that does not confer a survival benefit and also does not lead to a disadvantage. A bad mutation results in a change that leads to the death of the organism or confers a disadvantage to survival.
Obviously, good mutations are passed on with greater frequency because those individuals reach reproduction more often than those with neutral or bad mutations. Neutral mutations may or may not be passed on while bad mutations generally die out. Now, the terms good, neutral, and bad are simplistic, but they get the general point across. The point: DNA mutates randomly due to errors in copying as the DNA is passed from one generation to the next. The mutations may or may not confer an advantage onto the next individual. Those mutations that provide an advantage are passed on down the line through subsequent generations.
The reason that evolution takes so long is that mutations in DNA do not occur commonly and when they do occur, they may be neutral and result in no overall physical change. The low rate of mutation in DNA means that it takes thousands (sometimes more) of years for organisms to change. Darwin did not know about DNA or mutations during his lifetime, but his theory turned out to be predictive of what science would learn about DNA and heredity in the 1950’s and on. Darwin stated that random changes in individuals conferred changes that were either advantageous or not. The advantages led to the individuals being more likely to reproduce and thus those changes being passed on. Nearly 100 years later, science learned that those changes occurred through mutation in DNA, which is the blueprint that is passed from parent to offspring.
Of course, this theory says nothing about the origin of life. What it does imply, however, is perceived as some to be a direct threat to religion. The theory implies the following things. First, the world was not created as it is. It was a very different place many, many years ago and organisms have changed over time. This is in direct conflict with the story in Genesis. Second, in order for evolution to take place, hundreds of millions of years are necessary to allow that slow rate of mutation to lead to the number of organisms we see today. Third, the theory takes humans out of a specially selected group and puts them among the descendents of ancient primates. The literal interpretation of certain religious texts is incongruous with the theory of evolution due to the implications of the theory. Those who do not subscribe to literal interpretations will find that evolution can easily be accommodated within most any religion. Religion is beyond the realm of science in the sense that it cannot be tested. Science deals with only those ideas that can be tested, religion cannot be tested. Science deals with natural phenomena with the goal of learning and establishing natural rules that can allow humans to reliably predict and understand the way the world works. Religion is a personal choice. The theory of evolution is a well-tested, well-established body of knowledge within science that helps scientists to understand the natural world and create solutions to the problems that face humanity. The choice is individual as to what each person believes to be the ultimate truth about the origin of the universe but for understanding the world and advancing the cause of science in such fields as bacterial antibiotic resistance, human genetic disease, the development of disease and drought resistant crops, and more, evolution is the only means the human race has by which to bring about those goals and better the lives of countless humans and other living organisms.