Struggle for existence
The struggle for existence refers to the constant competition between organisms to live. Originating in the late 1700s, the phrase “struggle for existence” first came to use in Thomas Robert Malthus’s An Essay on the Principle of Population. Malthus’s use of the struggle for existence came through his study of economics and populations.
Charles Darwin used the phrase “struggle for existence” as the title to the third chapter of On the Origin of Species. Using Malthus’s idea of the struggle for existence, Darwin was able to change his view of adaptation, which was highly influential in the formulation of the theory of natural selection. In addition, Alfred Wallace independently used the struggle for existence to help conclude on the same theory of evolution. Later, T.H. Huxley further developed the idea of the struggle for existence. Huxley did not fully agree with Darwin on natural selection, but he did agree that there was a struggle for existence in nature.
While the idea of the struggle for existence was developing in the western world, there were other interpretations of the struggle for existence, especially in Russia. Also, the struggle for existence was questioned in the United States in the 1930s, as the idea of cooperation among organisms became popular. More recently, it has been argued that the struggle for existence is not as important on macroevolutionary time scales.
Further Information: Natural selection
The idea of the struggle for existence has been used in multiple disciplines. It became popular in the mid 19th century, through the work of Malthus, Darwin, Wallace, and others. The most popular use of the struggle for existence is in the explanation of the theory of natural selection by Charles Darwin. For more technical information on how the struggle for existence is meshed with the theory of natural selection see the main article for natural selection.
In An Essay on the Principle of Population, Thomas Robert Malthus argues that a population will increase exponentially if unchecked, while resources will only increase arithmetically. However, Malthus knew that with limited resources on earth, there would be competition among people to exist and survive. The checks that exist on the human population growth result in a struggle for existence. Malthus also notes that the checks on the human population are more complicated than those on animals and plants. Malthus explains, for example, that a human check on population growth is the conscious decision not to reproduce because of financial burden. Malthus then explains that the main check on population growth is food. In periods of high food availability the population increases, while in periods of food shortages, the population decreases. Thus, "population [growth] tends to oscillate around its means of subsistence." The combination of Malthus's "law of multiplication in geometrical progression" and "the law of limited population" leads to the idea of the struggle for existence. Despite these ideas, Malthus was a religious man and believed in divine laws that governed the natural world.
Like many people of his day, Darwin once believed nature was perfect and harmonious. Even after initially reading Malthus in 1838, Darwin was not convinced on the idea of the struggle for existence. Darwin continued to believe in a more traditional, theological sense, including the notion of perfect adaption. The popular study of natural theology in this time period was an obstacle for Darwin's theory of evolution by natural selection. For example, natural theologians, along with Malthus, believed that preordained laws governed the natural world, which is not consistent with natural selection as it is known today. Thus, for weeks after reading Malthus, Darwin continued to believe that variations were part of God's larger plan. However, within a few months, Darwin gradually included the idea that adaptations were not from birth, but rather from external pressures. From Malthus, Darwin claims that the idea of a struggle for existence allowed him to see that favorable variations would be preserved while unfavorable variations would not resulting in the evolution new species. Supporting this claim, in about 1855, Darwin noted that the struggle for existence would produce diversification – leading to Darwin’s principle of divergence. T.H. Huxley, commonly known as Darwin's Bulldog, clearly explains the struggle for existence in terms of natural selection. Huxley explains that the struggle for existence is concluded based on the fact that populations grow geometrically if unchecked but populations tend to stay constant in number over time.
Alfred Wallace and Darwin independently arrived at the theory of evolution by natural selection. Similar to Darwin, Wallace used Malthus's idea of the struggle for existence to reach this conclusion. In addition, Wallace was influenced by Charles Lyell's Principles of Geology. Lyell discusses a struggle between organisms that causes one species to become extinct; Wallace may have taken the phrase struggle for existence from this example. Additionally, Wallace claimed that it was the collection of chapters 3-12 of the first volume of An Essay on the Principle of Population that helped him develop his theory. Then in 1853, Wallace first used the phrase "struggle for existence" when discussing the issue of slavery. By 1855, Wallace had made connections between the struggle for existence and overall population. Wallace saw in Malthus's writing how there are different ways in which a population can be kept in check:
"From "the law of multiplication in geometrical progression" (the fact that all species have the power to increase their number up to as much as a thousandfold per year) and "the law of limited population" (the fact that the number of living individuals of each species typically remains almost stationary), one deduces that there is a struggle for existence." 
Wallace combined the idea of the struggle for existence with variation to argue for the idea of "survival of the fittest."
In Russia, the idea of "mutual aid" was used to explain evolution rather than the struggle for existence. Peter Kropotkin wrote the book Mutual Aid: A Factor of Evolution in response to the idea of evolution by natural selection. Due to the vast landscape and lack of population in proportion to land, many people of Russia did not see the struggle for existence and could not relate to Malthus's ideas on population. Thus, it was concluded that cooperation, which is more successful in battling the abiotic environment, rather than competition is a driving factor in natural selection. Rather than a struggle for existence, a mutual struggle and mutual aid drives natural selection. Kropotkin believed that Wallace and Darwin saw the struggle for existence because of their coastal location and overpopulated areas of study.
During the 1930s in the United States, a shift in scientific perception caused scientists to lean away from the use of the struggle for existence to explain Darwin's ideas, and more toward the idea of cooperation for mutual benefit. Warder Clyde Allee, famous for the Allee effect, also supported this idea that cooperation in addition to the struggle for existence drove evolution. Finally, Alfred E. Emerson supported similar claims around this time period. Emerson saw a struggle for existence on the individual level, but he saw the struggle necessary on a population level for keeping the ecosystem in order.
Today, the struggle for existence is a widely accepted idea that helps to explain and justify the theory of natural selection. However, K.D. Bennett argues that the struggle for existence is only present on geographically small scales. He notes that "As climates fluctuate on Milankovitch time-scales, the tendency for populations to increase exponentially is realised, distributions increase enormously, and any struggle for existence is relaxed or eliminated."
- Ospovat, Dov. The Development of Darwin's Theory: Natural History, Natural Theology, and Natural Selection, 1838-1859. Cambridge: Cambridge University Press, 1981.
- Petersen, William. Malthus. Cambridge, Massachusetts: Harvard University Press, 1979
- Paradis, James G. T.H. Huxley: man's place in nature. Lincoln: University of Nebraska Press, 1978.
- Todes, Daniel Philip. Darwin without Malthus the struggle for existence in Russian evolutionary thought. New York: Oxford University Press, 1989.
- Mitman, Gregg. From the Population to Society: The Cooperative Metaphors of W.C. Allee and A.E. Emerson. Norman : Journal of the History of Biology , 1988. Print.
- Bennett, K. D. Evolution and Ecology: The Pace of Life. Cambridge: Cambridge University Press, 1997.
- Petersen, William. Malthus. Cambridge, Massachusetts: Harvard University Press, 1979, 56.
- McKinney, H. Lewis. Wallace and Natural Selection. New Haven: Yale University Press, 1972
- Petersen, William. Malthus. Cambridge, Massachusetts: Harvard University Press, 1979, 220.
- Todes, Daniel Philip. Darwin's Malthusian metaphor and Russian evolutionary thought, 1859-1917. Philadelphia: University of Pennsylvania, 1987. Print.
- Bennett, K. D. Evolution and Ecology: The Pace of Life. Cambridge: Cambridge University Press, 1997, 188.