91短视频

Cindy Chen

In studying the history of science, biology is often a matter of special examination. And in investigating the course of this field one major subject of concentration, aside from looking at the greatest contributions made into this area and the scientists that made them, is the history of evolutionary thought. To this matter one will almost always become familiar with Charles Darwin, perhaps the greatest of all contributors. As a naturalist, Darwin was not only responsible for the theory of evolution as we know it today, but also the foundation that biological sciences are based on. His theory of natural selection as a mechanism for change over time in all species of life brought him a lifetime of praise and admiration, in addition to a great deal of criticism. Darwin’s theory was met with disapproval in two major areas, the scientific and the social. Most scientists during that era had grown comfortable with the reductionist approach of all events and models being fixed and deterministic, thus Darwin’s theory was rejected because it seemed to rely only on chance events and not on pure physical laws. Hence, regardless of whether the characteristics were being favored or not, no one believed that certain “preferred” traits would have a higher possibility of being selected to be inherited more frequently than other “unfavorable” ones. Darwin was also given much criticism in the social realm. Having been opposed to the theory of special creation or creation by design, which was widely accepted during 19th century Britain, Darwin’s thoughts were seen as anti-religious and the cause of great debates. In all, to comprehend the complete work of Darwin it is essential to know not only his scientific achievements, but social influences as well.

Charles Darwin was born in 1809 to a wealthy middle-class English family (Wall 2003). Expected to follow in his father’s and grandfather’s footsteps, Darwin was sent to the University of Edinburgh to acquire the knowledge to become a physician. His medical interests did not last long, and after only one year he dropped out of school. Wanting a respectable future for his son, Darwin’s father sent him to the University of Cambridge to study for the ministry. Although without enthusiasm, Darwin at that time had whole-heartedly believed in the words of the Bible (Bowler 1983, 1989), and entered the school prepared to follow the reasoning of Reverend Paley’s Design Argument. In the words of Paley himself, this argument can be described as follows,

Living organisms are complicated in a degree which exceeds all computation. How else to account for the often amazing adaptations of animals and plants? Only an intelligent Designer could have created them. That designer must have been a person. That person is GOD (Paley 1802).

Though Darwin took up the study of Natural Theology as an avid admirer of the Design Argument, it would not be long before Darwin renounces this belief that God created all the species on earth due to his own observations of imperfections in the design, which would not be possible if there were a benevolent Creator (Hartwig 2003). Upon entering Cambridge University Darwin became good friends with the botanist Reverend Henslow. This friendship would eventually allow Darwin the opportunity to embark on a voyage with the H.M.S. Beagle as a gentleman-naturalist. When Reverend Henslow was asked by Captain Fitzroy of the Beagle to recommend a wealthy, well-educated man to observe and take notes on all flora, fauna, and geological findings during the course of the journey, Henslow strongly suggested Darwin. With the alternative of taking up the position of a country parson at the end of his education, Darwin eagerly agreed to fill the opening aboard the Beagle. In accepting the position of being a gentleman-naturalist, Darwin unknowingly also opened the door to a scientific revolution and would lay down the foundation for future biological studies.

On his travels with the H.M.S. Beagle, Darwin observed many species of plants and animals throughout the voyage. He also noted that there were obvious variations in the species that he noted to be correlated with the changes in the climate. But this conclusion became less and less evident as he sailed through the archipelago, where many species of flora and fauna were witnessed to have discrepancies in various traits while the climate still seemed to be almost without change. This deviation from his earlier deduction was even more apparent during his observations of the plant and animal species of the Galapagos Islands, a group of about nine small islands all lying about the equator approximately 1,000 miles from South America. Throughout his exploration of these islands Darwin found that even with a steady climate for all islands, the inhabitants of each island still had visible differences. Fascinated by what he saw Darwin carefully logged all that he observed, and drew detailed sketches of the varying traits. One species that was of particular interest to Darwin were the finches of the Galapagos, whose traits he carefully noted. With the assistance of an ornithologist, Darwin determined that the Galapagos finches were all associated, yet still possessed distinct characteristics, ranging from body height to body length. But the trait that Darwin focused on most was the finches’ beaks, which he noticed to be different for the birds of each island. He noticed that some finches had large rounded beaks, while others had less rounded beaks or smaller beaks, and still others had narrow pointed beaks. He observed that all beaks were specialized for the birds to better obtain food on each specific island, whether it is to crack open the abundant amount of nuts on a certain island or dig in the worm-filled soil of another. As he surveyed the islands, Darwin drew from his records of the beaks and the type of food available in each habitat, and was successful in concluding that the variations observed were advantageous for each species in order to survive. In addition to this, with the knowledge he had gained from reading Lyell’s essays on evolution as a process of uniformitarianism, where all physical characteristics of the Earth were attributed to natural causes operating in an uniform manner over long periods of time, along with the evidence he had collected of the distinct features of the animal and plant populations and the ancestral fossils he found on the islands, Darwin was convinced that these variations could not have happened by random or taken place in just a short amount of time (Wall 2003). Hence these differences were due to slow modifications occurring in a consistent way from their ancestral forms. In other words, they evolved over time. Yet even with the success in figuring out that the differences in traits came by way of gradual evolution, one thing still occupied Darwin’s mind; he could not find the answer for why these variations occurred.

In search for a mechanism to explain the process of evolution he deduced to have taken place on the Galapagos Islands, Darwin settled in London upon his return from the five-year expedition and committed himself to working out the puzzle of inheritance. In his quest for the answer Darwin came about Reverend Thomas Malthus’ book on population in 1838, which states that with the human population increasing at a rate significantly higher than that of the most optimistic rate for the growth of resources, the human race would eventually end up competing with each other for food in order to survive. In competing for these resources, some would have an advantage such that the better equipped you are the higher the chances of obtaining these means. From this, Darwin concluded that the competition for limited resources predicted for the human race could also be applied to animal and plant species as well, to explain the observations he gathered on the Galapagos Islands. If the rate of increase in both flora and fauna were also vastly greater than the resources that sustain their survival, there too would be a competition for food. And in this struggle the victors are those who are equipped with the traits that would allow them to obtain the food and continue to live, while the failures are those who lack those qualities. Hence the qualities producing the advantages would be preserved via an increased frequency of passing on the genes that create these traits, and the unfavorable ones destroyed with the eventual fading out of these characteristics from a lack of being inherited by offspring (Molles 2002, 1999). With this deduction and from what Darwin already believed from Lyell’s theory of change over time, Darwin formulated his theory of evolution by natural selection. But it would be many years and many drafts before he would share his revolutionary theory with the rest of the world.

When Darwin finally felt confident enough to share his work with the rest of society, it was nearly seventeen years after he had produced his first draft. Afraid of being over shadowed by another naturalist named Alfred Russel Wallace, who had witnessed the same incidents of the transformation of species on a trip to the Amazon as Darwin did in the Galapagos Islands, and who also intended to write a book explaining the means of evolution after the publishing of his first essay on the coming to existence of species, Darwin hastily complied a five hundred page abstract of his theory, which was published on November 24, 1859. His essay titled On the Origin of Species By Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, summarized would read as follows:

If during the long course of ages and under varying conditions of life, organic beings vary at all in the several parts of their organisation, and I think this cannot be disputed; if there be, owing to the high geometrical powers of increase of each species, at some age, season, or year, a severe struggle for life, and this certainly cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred useful to each being's own welfare, in the same way as so many variations have occurred useful to man. But if variations useful to any organic being do occur, assuredly individuals thus characterised will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will tend to produce offspring similarly characterised. This principle of preservation, I have called, for the sake of brevity, Natural Selection (Darwin 1859).

As logical and acceptable as Darwin’s ideas of the preservation of advantageous variations resulting from those traits being inherited by the offspring of the survivors in the struggle for life, which in turn was caused by changes in the environment over time may seem to readers and scientists today; these ideas were not as palatable during Darwin’s era. As mentioned earlier, much of the scientific community of 19th century Britain rejected Darwin’s theory, mainly on the basis of his theory being too dependent upon chance events. With the focus of science having moved from uncertainty to certainty, any scientist would need to provide a rigid conclusion that could be supported by hard evidence to get the acceptance of others. Many scientists felt Darwin failed to do so, and that his theory of evolution was established on a number of assumptions. He first supposed that Lyell’s theories were correct and that the earth was old, having evolved over countless years. Along with this he presumed Malthus’ concept of a struggle for food and survival in the human race due to high birth rates and slow resource reproduction could also be applied to the flora and fauna species as well. Then he assumed that this struggle would result in chance selections of certain advantageous traits that would be passed on to offspring. In addition to these objections, it was even harder for others to accept his ideas, for the views of numerous biologists were that all traits would be inherited equally by the offspring from any parent. For instance, if a red flower and a white flower mated it was expected for the progeny to exhibit a pink flower, there would be no ‘selection’ for the better color, just as there would be no natural selection for more beneficial traits. With his premises based on postulations and a lack of evidence to prove that inheritance of beneficial characteristics occurred at higher frequencies Darwin’s theory was snubbed by many of his colleagues.

Another, and perhaps the most immense, source of rejection towards Darwin’s theory of evolution came from the social realm. Belief during the 19th century was very much centered on religious values. Stemming from this the traditional belief was the Design Argument, or that the view that designs in life were too complex, and therefore must have been created by a benevolent God (Bowler 1983, 1989). Having been a supporter of this theory originally, Darwin was seen as a traitor who had broken ties with convention. His certainty in the fact that natural laws were the cause of evolution in a competitive world where only the fittest would survive was an out right stand against the creationism. Although this criticism of being an atheist swayed Darwin somewhat, in that he began to isolate himself from the rest of society only keeping in touch with a few trusted friends, he was steadfast in his beliefs and did not return to the argument from design. In fact, in order to redeem himself among the scientific society, Darwin made grounds for his theory by attacking the theory of Design. Darwin first claimed that the logic behind the Design Argument was faulty because it did not exclude the possibility of other mechanisms in the creation of the designs. The fallacy in the argument is seen when it is set up as a syllogism. Written in this form, the argument would read, that the hypothesis that God created all the species on earth is evidenced by the intricate designs observed in nature, so that the hypothesis implies intricate designs and in turn the intricate designs implies the hypothesis. But when Darwin’s theory is arranged in the same manner, stating that his hypothesis of evolution by natural selection can also be evidenced by the designs in nature, so that his theory also implies the existence of these designs, and in turn the designs too implies his theory is possible. There in lies the fallacy, the logic behind the argument for design is invalid in that both explanations have form; the hypothesis of God or evolution would both imply intricate designs, and intricate designs can imply both hypotheses (Wall 2003). Therefore, even though Darwin did not disprove the Design argument completely, he succeeded in making his case seem plausible using the logic of the opposing view, and in doing so disrupted the foundations of the case for an intelligent Creator. With this assertion made, Darwin was able to regain new grounds for his theory, and in turn gather some support and confirmation.

In conclusion, although Darwin still did not figure out the puzzle of inheritance, he is still considered one of the greatest, if not the greatest, contributor to the field of biology. His revolutionary theory of evolution by natural selection allowed people to break free from the traditional belief of special creation. It also gave them the opportunity to build their works on a purely scientific foundation. Through immense disapproval and doubt, Darwin was able to find ground for his theory, and hence allowed for its prevalence into today’s science. Of course, there are still those who believe in an all-mighty Creator and even to this day many schools debate which side of the story to tell. Even though all are entitled to their beliefs, I personally am a supporter of the Darwinian school of thought, and am grateful for the observations that he made which led to the theory of evolution I know today.

Works Cited

• Bowler, P.J. Evolution: The History of an Idea. Berkeley, CA: University of California Press. 1989.
• Darwin, C. The Origin of Species by Means of Natural Selection: Or, the Preservation of Favored Races in the Struggle for Life. London: John Murray Publishers. 1859.
• Hartwig, M. March 9, 2003. What is Intelligent Design? Access Research Network.
• Molles Jr., M.C. Ecology: Concepts and Applications. New York: McGraw-Hill Companies, Inc. 2002.
• Paley, W. “Natural Theology: Excerpts” in But Is It Science? Ed. M. Ruse. Amherst, NY: Prometheus Books, 1996. pp. 46-49.
• Wall, B. Glimpses of Reality: Episodes in the History of Science. Toronto: Wall & Emerson, Inc. 2003.