What is Struggle for existence?
The '''struggle for existence''' is a [[natural history]] [metaphor]. It refers to the competition between [[organism|living things]] to survive. This, and the similar phrase ''struggle for life'', were used over 40 times by Charles Darwin in the ''[[Origin of Species]]'',<ref>Barrett P.H. 1981. ''et al'' ''A concordance to Darwin's Origin of Species''. Cornell University Press. p725.</ref> and the phrase is the title of chapter 3 of the ''Origin''. Darwin got the idea from his reading of the 6th edition of [[Thomas Malthus]]' ''Essay on the principle of population'',<ref name=Malthus1>Malthus T.R. 1826. ''Essay on the principle of population''. London, 5th ed.</ref> and [[Alfred Russel Wallace]] also used the phrase regularly. The idea is actually much older,<ref>see Mayr, Ernst 1982. The growth of biological thought. Harvard University Press, p493.</ref> and many natural historians have noted the competition between animals. Generally speaking, they have been interested in the competition between [[species]]. Malthus was probably the first to think about the struggle for [[resource]]s between members of one species – humans. Darwin first heard about Malthus in letters from his sister Fanny, while he was voyaging on [[HMS Beagle|HMS ''Beagle'']]. Fanny told him Malthus' ideas were being promoted by [[Harriet Martineau]], an early [[feminist]] writer.<ref name=Darwin>Desmond A. & Moore J. ''Darwin''. 1991. Joseph, London.</ref><sup>p153</sup> Later on, back in [[London]], Darwin met Martineau over dinner, and put a lot of thought into the ideas of Malthus. The number of humans could double in 25 years. If they did not, it was because of competition for resources, such as food, or because wars and disease became more common. Darwin began to realize that every species of living thing has the potential to increase geometrically (2, 4, 8, 16, 32, 64, 128, 256, 512, ....), yet this pattern of [[population growth]] does not happen in practice. Darwin explains why organisms do not increase geometrically. His reasons