Theory Of Evolution Through Natural Selection example essay topic

Charles Darwin Chad Galloway More than a century after his death, and four generations after the publication of his chief work, 'The Origin of Species', Charles Darwin may still be considered the most controversial scientist in the world. His name is synonymous with the debate that continues to swirl around the theory of evolution, a theory that deeply shook the Western view of humanity and its place in the world. We tend to speak simply of the theory of evolution, leaving off the explanatory phrase, 'through natural selection. ' At most, perhaps, the general public has heard of 'survival of the fittest' a poor phrase as far as I'm concerned, since fitness in everyday usage is associated with physical conditioning and athletic ability. 'Survival of the most suited to its environment' would be a more accurate, and convincing expression for this pedicular concept. But to most of us, 'evolution's imply means that human beings are descended from apes, a slight misunderstanding, since both humans and modern apes are descendants of a mutual ancestor that is now extinct.

It's not evolution but the theory of natural selection and the evidence he collected to prove to fellow scientists, peers, students, and most importantly the masses of public and the church that were at the heart of Darwin's contribution to biological science. Charles Darwin did not invent the concept of evolution. A number of prominent scientists and other thinkers during the eighteenth century and the first half of the nineteenth century (among them Charles Darwin's grandfather, Erasmus Darwin) had offered detailed theories of evolution (Clark, 1984, pg. 24-25). Therefor the idea of evolution went very far back in Western history.

At that time this concept was referred to as The Great Chain Of Life and was conceived in the middle ages, based on a mixture of classical and Biblical ideas. The ranking order ranged from the 'lowest' forms of life to 'higher' living beings (lion), through the various classes of human beings from peasants to nobles to Popes, and upwards through the hierarchy of angles to God. This concept, in and of itself, has nothing to do with evolution, in fact it seems to be anti-evolutionary, since every member is fixed in its own place. This chain was created in a time when the world was considered to be more static rather than a diverse collection of dynamic ideas.

But the Newtonian revolution of the seventeenth century replaced the old static world with a new world view in which everything was naturally in motion. In the course of the eighteenth century the notion of progress, of gradual but relentless pursuit of betterment, began to take hold in western thought. It was only natural that the ideas of change and of progress should eventually be applied to the Great Chain of Being. The natural implication of a 'dynamic " chain of being was a sort of tree of life, gradually sprouting upward from basic primordial ooze, branching outward into all the varied species on our fine planet, ending with, of course, eighteenth century Man. This could be called evolutionary, but it does not offer a theory of evolution, an order in which evolution took place.

It was no longer acceptable to say 'God did it'. Therefor, if evolution was to ever become a science, a rational explanation had to be offered. Such an explanation was proposed by Jean Baptiste Lamarck toward the end of the eighteenth century, and Lamarck became best known for his pre-Darwin theory of evolution. According to Lamarck, the acquired characteristics of the parents could be handed down to their offspring. Suppose, to take the most over used example, that the first generations of giraffe had a neck of ordinary length. Because the lower branches of the trees they fed off were easily striped, these early giraffes stretched out their necks to reach higher branches.

In doing so, they caused their offspring to be born with slightly longer necks, until the ultimate result was the giraffe of today. This theory had virtues far beyond the necks of giraffes. Taking this concept to its extreme one would now be under the impression that all that the past European forefathers have passed on all their acquired traits to the younger generations following them. The reasoning powers of the great philosophers, the valour of Crusading knights should have been endowed in all rather than a meagre few. According to this theory of evolution descendants could one day attain the heights Europeans had already scaled. The Lamarckian evolution had only one crucial defect, it was entirely untrue.

One could cut off a rat's tail, but its offspring would have normal tails. The rules of genetics were not known in Lamarck's day, and were not known until long after Darwin's, when the pioneering work of Mendel was rediscovered at the turn of the twentieth century. But animal breeders had long since discovered certain principles of breeding for desired characteristics, and acquired characteristics played no part in this process. Only through proper training could one find out if a hunting dog had favourable qualities. But the training did not create those characteristics in the dog's offspring. Lamarckianism was now discredited, and the question of evolution remained a mystery.

Many scientists rejected evolution and the Great Chain of Life feeling that its concepts had no place in biological science. The key was produced by the theorist of the 'dismal science' of economics, Thomas Malthus. Malthus said that human (and animal) populations increased at a geometric rate, whereas food supply increased only at an arithmetic rate. Therefore population was continually outstripping food supply, and was kept in check only by starvation, or by indirect acts such as war and diseases. Malthusianism raised a very good question which is not easily noticed. Which individuals survived in hard times, and which died?

Luck was probably the largest factor, but not the only one, other factors applied, such as the strong, the courageous, or the adaptable had a somewhat better chance of surviving than those who lacked those characteristics. To the degree that strength, drive, or adaptability were acquired characteristics, they would have no effect on future generations since Lamarckianism had been proven wrong. But to the degree that some individuals inherited these characteristics, they were more likely to survive, to hand down these same characteristics to their descendants. As the lower branches of the ancient African trees were plucked bare, the longer-necked ancestral giraffes were more likely to survive than their shorter-necked cousins, and they handed down the tendency toward long necks to their descendants. The modern, long-necked giraffe thus evolved through countless generations of natural selection. A few people may have stumbled upon this idea before Darwin did, but Darwin was the first to develop it.

The development was indeed more crucial to the ultimate acceptance than was the insight alone. By itself, evolution by natural selection is an amazing theory, and although this might explain a great deal, it does not prove that it is true. Lamarckianism was amazing in its time but it did not stand up close to scrutiny. Before offering his insight to the world, Charles Darwin determined that he would subject it to close scrutiny. He spent the next two decades of his life collecting masses of evidence, from the distribution of natural species to the experience of pigeon breeders, to develop and support his argument. As far as he was concerned, Darwin was nowhere near ready to present his theory when, in 1858, Alfred Lord Wallace, sent a paper to him.

Wallace's paper stated the very theory that Darwin had been labouring on for two decades. Soon a joint paper was written and published, and the theory of evolution through natural selection was at least presented to the scientific world (Darwin and Wallace, 1858). Two years later Darwin published his full theory in The Origin of Species. If Thomas Edison said that invention was one percent inspiration and ninety-nine percent perspiration, Darwin showed that the same was true of discovery.

Evolution through natural selection was a brilliant idea, and one that might be debated endlessly. The process through which one species evolved into a distinctly different species was far too time consuming to be directly demonstrated. All the naturalists had available, apart from bones, was an understanding of the state of life as it is on earth today. Essentially, The Origin of Species approached the problem of evolution through two lines of argument and interpretation, both rooted in the concept of inherited variation. Darwin showed that the distinction between species was not hard and fast. There are varieties of a given intricately adapted to different conditions, that routinely interbred along the boundary between their home territories, but the mixed varieties tend to remain confined to the boundary area, since they are less adapted than either of the base varieties to their own home territories.

Specification in nature did not require dramatic jumps, but could emerge out of gradually widening variation. Darwin examined variation under domestication to demonstrate that the deliberate selection of breeders could produce varieties as markedly different from the root stock as the varieties found in nature. Deliberate selection through breeding was obviously a much faster and 'efficient' process than natural selection through differential rates of survival in the face of environmental pressures, but the end result would be essentially the same, the variety of a given species that was most adapted to a given environment would gradually replace the root stock in that environment. The theory of evolution through natural selection would most certainly have appeared, even without Darwin, it would have appeared at the same time, since it was Wallace's independent development of the theory that prompted his and Darwin's joint paper. The idea of natural selection was circulating in the mid-nineteenth century, just as the idea of evolution had been circulating in the eighteenth. But had the century of evolution through natural selection appeared only in outline form, it might have been many more years in winning general acceptance.

The collected evidence of The Origin of Species was sufficient to persuade most biologists that this was the key that they had been looking for. Quite a few scientists held out, notably Louis Agassiz, but the younger generation of students coming into the field seem almost without exception to agree to the adopted theory. Within a few decades, evolution through natural selection was a fundamental paradigm of biological thought. The development of biology through the century since that time has not essentially altered the situation. Alot of changes have been introduced, or at least debated.

Once genetics was more fully understood, it was realized that major steps in specification might just owe more to favourable mutations than to the regular process of variation. But the introduction of mutation did not change the principle of natural selection. Natural selection, as Darwin saw it, simply can not be ignored. For just as a largely barren earth is re-colonized by the survivors descendants, which must adapt through either variation or mutation to fill the ecological niches left empty by the prior extinctions. Just as an area devastated by a forest fire a refilled by an evolution of new forms, not by the existing ones from unburned areas.

We may not be able to see the entire history of evolution but from our viewpoint we have hundreds of examples of natural selection taking place all around us each and every second of each and every day. Fortunately, Charles Darwin (and maybe I should credit Alfred Lord Wallace) had the insight and boldness to conceive and develop a theory so controversial to his time and culture.

Bibliography

Clark, R.W. (1984).
The Survival of Charles Darwin. New York: Random HouseSproule, Anna (1990).
Charles Darwin. Concord: Irwin Warburton, Lois (1992).
Human Origins-Tracing Humanity " evolution. San Diego: Lucent Books Howell, F.C. (1980).
Early Man. Virginia: Time-Life Books Nouvelle, C (1885).