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Charles Darwin

The person usually cited as the key figure in our understanding and development of the theory of evolution is Charles Darwin. He was not the first to propose the idea of evolution, but he was the first to provide extensive support for the process, and he also postulated a mechanism for how evolution occurred.


Darwin’s ideas were born on a five year voyage he took around the world aboard the H.M.S. Beagle, beginning in 1831. Darwin was the ship’s naturalist, and he made extensive observations and collected specimens, most notably from up and down both coasts of South America and from the Galapagos islands, located off the coast of Equador.  His book, On the Origin of Species by Means of Natural Selection, was published 22 years after his return to England. Several observations helped Darwin formulate his theory.  These include: 
  • OverproductionDarwin noted that plants and animals produce many offspring, more than the number necessary for their own replacement. In other words, to replace themselves in a population, a mating pair of sexually reproducing organisms need only have two offspring. The production of large amounts of offspring means that growth will occur in an exponential fashion, creating a huge population in only several generations. In reality, however, this exponential growth is not seen. Many factors limit the population size, some which are discussed below.
  • Variation:  No two individuals are exactly the same. There is always some variation, something that is different, among individuals. In addition, these variations can be passed on from parent to offspring, as shown through selective breeding of domesticated plants and animals. Darwin did not know the mechanisms behind this process (and Mendel’s work was not recognized at the time), but it was obvious that traits were inherited.
  • Competition:  All species require certain resources in order to survive. Some things, such as soil, food and water, are in limited quantities in the environment. Therefore, different species compete for their use. In addition, a population reproducing geometrically will put individuals of the same species in competition with one another.
  • Survival and reproduction of the fittest:  Competition results in the survival of some organisms over others. Certain variations will contribute to this survival, and individuals who posses these traits are more likely to reach reproductive maturity. Therefore, the offspring of these individuals will inherit these traits and will have a better chance at survival. In this way, beneficial traits are selected and eventually will increase with frequency in the population.
Thus we can see that overproduction produces a large number of individuals, each having different variations. Competition between species and among individuals of the same species results in survival of the fittest. The best of each generation reproduce and pass on these traits to the next generation. From these observations, Darwin postulated a mechanism that would explain how these factors contribute to evolution. This process is known as natural selection and is the cornerstone of the theory of evolution. 

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