Few books have caused such turmoil as the Origin of Species by Charles Darwin. It was originally published in 1859, under the title, on the origin of species by means of natural selection or, The Preservation of favored races in the struggle for life (Darwin 2004). The whole book and theory, if broken down into simplistic terms, just says that all living things developed down from a single ancestor and complex things developed from simple things. When genetic mutations happened over time, the beneficial alterations were kept, which the author termed ‘natural selection’ and were passed on to the next generation and the process is continuing (Darwin’s theory of evolution 2009). The theory had such a profound impact on the world of biology that the phrase “nothing makes sense in biology except in the light of Theory of Evolution” came into existence. Darwin’s Theory of Natural Selection has engendered the “Darwinian Revolution”. Along with Darwin, his close associate, Alfred Wallace is also given credit for the theory 1. While traveling aboard the HMS Beagle for over two years, he observed the fossils in South America, the Ostriches of the pampas and the finches in the Galapagos Islands that triggered the research, leading to the proposition of the theory of Natural Selection 2.
The Theory and its Implications
Darwin and Wallace based their assumptions on seven basic factors that proved the existence of natural selection. These are Geology, Fossils, Island life, Overproduction of individuals, extensive variation seen in individuals, these variations were inheritable and effects of artificial selection. 1. It was found that geological procedures have been consistent throughout time. These showed that earth was considerably old. A glance at the present is enough to see the dynamics that shaped the past. Even slight changes that go on for a long period of time could have a large-scale impact, in Biology. 2. Even though extinct, certain forms show a distant connection with the ones living. It implied a thread of evolution running through both. 3. While studying Galapagos Islands, it was found that the species within the islands were slightly different from the counterparts in the mainland. This led to the conclusion that the species that live in islands evolve in isolation and thereby evolved slightly differently. 4. According to Malthus, it was found that species reproduced exponentially. Even though offspring abounded, most of them did not reach maturity. This indicated a process of selection going on which decided the members to reach maturity and reproduce. 5. They also found that there were considerable variations within the individuals of a species. Both being taxonomists, they found that even the wild species were not an exemption. 6. These differences were also innate. Even physiological traits, textures and body shape, vulnerability to certain types of diseases etc., were also found to be inherited. 7. While examining the methods of artificial breeding and its effect on the domestic animals, it was found that some variations were favored and others were disfavored. Others were neutral even. These observed facts guided Darwin towards the theory of Evolution and the principle of Natural Selection.
The Theory indicates that if a population of a particular species developed a functional advantage, like learning to fly, the progeny of the particular individual species would inherit the advantage and consecutively all the oncoming generations. The inferior ones that remain behind would gradually die out. Natural selection means that the functional advantage of any particular species would be preserved and the remaining inferior members of the species would die out, leaving only the superior ones 3. This is like domestic breeding where only the superior quality of a species is allowed to breed, leaving out the inferior ones. Natural selection singles out and discards the inferior members of a breed over time. This meant that only those that are fittest would survive. Here fitness means reproductive success [‘Survival of the fittest’ is a term that was not coined by Darwin] 4. Darwin also wrote that these changes could not take place in giant leaps. It would take place only in slow and sure steps. Thus if any species contained a complex organ which could not have been formed by numerous, slow, and successive steps, his theory would absolutely break down. Such changes also could not take place to individual members of a population. It would happen to the whole population over periods of time 3.
He states that the whole species must have developed from a common ancestor, which was the simplest organism and from an event that took place by random chance first form of life dawned on earth. It is the development from simple to complex 5.
While thinking about the process of natural selection, three basic things have to be kept in mind.
- We need to know that only heritable variations are amplified or diminished. This is because of the fact that genes control these variations. Evolution happens because of the ability of genes to mutate. Genes are actually chemicals that contain coded information in the form of DNA. Though gene mutations are random, natural selection happens involving other factors.
- The whole population of a species gets involved in the process of Natural Selection. This means that it does not happen to one or two individuals of a species, it happens to the whole community, in the context of whole populations.
- This process of natural selection depends on the environment. When the environment is friendly to a particular aspect of the species, the members not comfortable with the aspect tend to end up in lesser numbers. If the environment alters, the species could return to its original ratio of existence. The variations, found because of natural selection, if favored by the environment, give rise to phenotypes. A little of the variations may turn into adaptations. There are genetic reasons for variations to become adaptations and adaptations are a result of Natural selection 6.
Often while considering the evolutionary chain, only the evolution between organic creatures is considered. If we expand this universally and try to indicate the universal evolution cycle into this, we could divide the whole into seven evolutionary stages.
- Cosmic evolution
- Stellar evolution
- Chemical evolution
- Planetary evolution
- Organic evolution
- Macroevolution and
- Microevolution. Of these scientists say that only the last evolution may be observed and the others are just assumptions 7.
But even though evolution is not observable directly, there are evidences which prove the theory to be true. First, we have to consider fossil evidence. While arranging fossils chronologically, we are able to notice a gradual change in the structure and formation of characteristic limbs of several species. Horses are a species, which shows a very evident evolutionary trait. Next comes the proof that Natural selection can evidently produce evolutionary change. It is pointed out that birds like the finches [Darwin’s finches of the Galapagos Islands] are favored to have stouter beaks, when only dry seeds are available to them. Artificial studies are indicative that evolution favors natural selection. When researching, we find evidences pointing to natural selection in other fields of Biology, like: The Anatomical record where often common share ancestry for organisms is found. The Molecular record indicates that the genes of organisms shown to be closely related by fossil records are also more similar than the ones distantly related 8.
Evidence also indicates that there are body parts that have been found to be remnants of our evolutionary past like the appendix, the tonsils etc. These body parts have been found to have no evident function at all within the body but they still existed 9.
Now when the world has moved on to the next era after the publication of the book, it still holds its relevance and its fight against its critics. The theory has raised many controversies. Darwin’s critics mainly raise the following objections to his theory.
- First the ‘theory’ is just a theory. There is no solid ground for the theory. We are not certain about the facts given in the books and in science theory means the basis on which we can rely on. This argument has even lost ground because even the theory gravity is just a theory.
- Another thing pointed out during the time, was that the absence of the fossil intermediaries. But this argument has lost ground in recent times because the absent fossils have been dug up.
- Another argument is what Darwin himself has said in his book, it was difficult to imagine that the eye had developed with intermediaries, which he felt to be ‘irreducibly complex’. Even this argument has broken up because intermediate eyes have been dug up. These intermediaries arose for the reason that they discovered light, and it was better than not being able to identify it at all.
- Next argument is that the order of things is usually lost by the occurrence of random events as stated in the second law of thermodynamics. However, the Complete law stated is that for a closed system and the earth, which receives energy continually from the sun, is not a closed system at all.
- The formation of proteins by chance is a technical improbability, say the opponents of Darwin. But this too was proved wrong in that probability theory cannot be used to argue backwards.
- Another case is that Natural selection does not entail evolution. We cannot find a fish developing wings and leaping away from predators in any of the experiments that have been conducted. But biologists argue that even in the case of lab experiments with dogs, breeds that cannot interbreed have been produced. This is also the case with evolution. Radically different species like fish and amphibians did have a common ancestor, which is indicated by fossil records.
- Then, the argument of the critics like the irreducibly complex argument goes for the improbability of the complexity of a cell which cannot be explained by evolution from simpler stages. They seem not to understand that this happened eons ago and was set up stage by stage. A complex blood clotting system has reached what it is now, after being initiated around 600 million years ago. This is still present in some varieties of fish. Later the complexity increased to reach what it is today 10.
- The body parts, which have no evident functionality, have recently been found to have uses that were unknown in the past. This too is used by critics. But such arguments are baseless and the new found functions of body parts like the appendix are neither an indication of the fallacy of the theory of evolution or a proof of it 11.
Even though the concept of evolution was nothing new to the world of science, and many scientists preferred this to the concept of creation, they were not able to give an explanation to the process of evolution. Charles Darwin gave a grip to such, by his theory of natural selection, explaining how evolution was spearheading forward. Well debated throughout the centuries, and often misinterpreted by many like Hitler, Darwin and his theory is still going ahead, strong even after 150 years. Charles Darwin viewed evolution as an constant struggle to bring out the fitter species. That every species fights for life, is a fact accepted by everyone. Neo Darwinism tries to reconcile the problem of accommodating Gregor Mendel’s theory, which states that species cannot be altered, with the theory of natural selection. Even with the number of tens of thousands of ‘irreducibly complex’ systems at the cellular level, the cards pass on and on to both sides of the table. Most often people believe and accept that Darwin’s theory is the most acceptable for evolution. However, they do not go further to state that it does not prove evolution 12.
There have been many significant evolutionists in modern times who have revised the Darwinian theory of evolution. Under the light of modern inventions and developments in molecular science, the Darwinian science of evolution is now taking flight with new wings adapted for the horizon 13.
Campbell&Reese. Principles of Evolution.
Darwin, Charles. The Origin of Species. London: Collectors library, 2004.
Evolution: Darwins theory. Web.
Johnson, George. 2008. The Evidence for Evolution.
Theory of Evolution. 2009.
Thomas Huxley. 2009.
Wallace&Darwin. Principles of Evolution.
- large ground finch Geospiza magnirostris;
- medium ground finch Geospiza fortis;
- small tree finchCamarhynchus parvulus;
- warbler finch Certhidea olivacea.
These photographs show color variants of the peppered moth, Biston betularia. Tutt proposed that the dark moth is more visible to predators on unpolluted trees while the light moth is more visible to predators on bark blackened by industrial pollution.