.. this revelation shortly before Origins was published, Darwin had long been in development of this theory. Wallace amicably relinquished the idea to Darwin, allowing him to become the first pioneer of evolution. Darwin was not driven to publish his finding, which hed been collecting for several years before Wallace struck upon it, because he had never come across a single [naturalist] who seemed to doubt to permanence of species (Ridley, pp. 70).
What follows are the key points of Darwins Theory of Natural Selection taken directly from the two chapters concerning it in his book Origins. In chapter III of Origins Darwin sets up his discussion on Natural Selection by establishing the struggle for existence in nature. By this he means not only an individuals need to fend of enemies and survive its environment but also its ability to create living, healthy, successful offspring. The first factor concerning this struggle is the ratio of increase in any given species. Darwin explains how this struggle must be occurring otherwise a single species would dominate the entire earth because every single one of its offspring would survive. This is due to the fact that every species reproduces exponentially, a rate that would soon produce astonishing numbers if left unchecked. This does not happen however, because nature has a system of checks and balances.
Although we may not be able to detect these checks, we can see their effects by the indisputable fact that one species doesnt completely dominate the planet. These checks consist of enemies eating the young or even adults, the rigors of weather or environment, and countless others. In this way birds, for example, cannot populate beyond their food supply, and the grains they feed on are held in check, because even though they may produce thousands of seeds only a few are able to reach maturity. Darwin goes on to show how all plants and animals compete and relate to each other in this struggle for existence. He does so by relating various personal observations that show the introduction of a different species of plant or animal can have a direct effect on the present survival of the indigenous species and even allow other foreign species to proliferate.
This leads to interspecies survival, which Darwin considers the hardest struggle of all, and the one that may have the greatest effect on the evolution of a species through Natural Selection. It springs forth from the similarity in habits and constitution. Plants and animals of the same species must compete for the same food and the same space to live in. Also, the original make-up of a plant or animal may give it an advantage to thrive in an ever-competitive environment. This brings us to Natural Selection and survival of the fittest that Darwin is most known for.
Darwin begins chapter IV by comparing human selection to natures ability to select, dubbing his theory Natural Selection, and explaining how imperceptible it is for us (at least science in his time) to examine the minute changes slowly taking place in nature. Variations in a species now come into play, and how these adaptations concern Natural Selection. Slight differences in an individual of a species will give rise to two situations. One is that it will be an injurious variation, which will definitely lead to the death of the individual because of the aforementioned struggle for existence. The other is a favorable adaptation in the individual’s ability to gather nutrients, survive its enemies, survive its environment, etc.
The chance of this individual surviving is greater than its less adapted competitors, however slight, which gives it a better chance of leaving progeny. These progeny will also have these abilities, increasing their chances of survival. Changes in the young can also bring about changes in the adult, as the individual approaches maturity, due to the difference in its original constitution. Once again, it will possibly leave new traits to its progeny (if they are advantageous and this variation doesnt die out), spreading the variation throughout the community and continuing the cycle of evolution. This is also known as ordinary selection because it begins with one individual and its constitution and habits.
Another method of Natural Selection is sexual selection. Sexual selection arises from interspecies cross breeding. This, Darwin explains, deviates from the struggle for existence and becomes the struggle for progeny. Advances in an individual will often allow it a better chance to procreate. A males ability to woo the female by singing, shows of strength, or decoration have definite effects as to whether or not he will be able to mate. The same goes for the females ability to attract the males attention.
Some of these techniques or differences can also sometimes be used in the struggle for existence giving that particular variation the advantage. Lastly, Darwin explains extinction and divergence of character in relation to Natural Selection. With extinction Darwin shows it is necessary for the adapted variation to proliferate. As the adapted variation begins to increase in numbers because of its greater ability to survive conditions, it’s obvious the older variety must become rarer. Rarity is the first sign of extinction, because with smaller numbers, there is a smaller chance of propagating, and a smaller chance of adapting.
This will eventually lead to complete extinction. Darwin places much importance on the divergence of character within a species, also. It explains how such a slight variation can lead to distinct species. It resides on the basis that each of the variations is added generation upon generation. These favorable adaptations when all put together make variations that are markedly different from the original progenitor.
All of this combines to form new, distinct, better adapted life forms which have, since the beginning of life on earth, been evolving into the diverse, lush, beautiful variety we experience everyday. Bibliography : Darwin, Charles, The Origin of Species by Means of Natural Selection. New York, Random House Inc, 1859. Ridley, Mark, The Darwin Reader. New York, W. W. Norton and Co, 1987.
Bibliography Darwin, Charles, The Origin of Species by Means of Natural Selection. New York, Random House Inc, 1859. Ridley, Mark, The Darwin Reader. New York, W. W. Norton and Co, 1987.