Malthus’s Law
Population when unchecked increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio.
Thomas Robert Malthus reasoned in An Essay on the Principle of Population (1798) that improvements in living standards among the poorest people were doomed to failure because of this law. While the means of subsistence might increase steadily, they would do so, he argued, only in an arithmetic ratio or series (such as 3 6 or 12) and thus would be overwhelmed by increasing numbers of people with population growing in a geometric progression (e.g. 3 9 27 81). But for the effects of war pestilence famine and - a possible palliative that he recommended in an 1803 revision -Â “moral restraint”, meaning premarital chastity and postponement of marriage, population would always increase faster than food supplies.
Malthus’s Law may not be exactly right. Two hundred years have gone by and humanity has managed so far to escape the Malthusian bind, thanks to the opening of new areas to farming and improvements in agricultural techniques. Still, with the world population now doubling about every fifty years it is hard to argue with the trend of his conclusions or, short of embracing war pestilence and famine, to visualise a solution to the population problem other than what some people call “immoral restraint” i.e. birth control.
Malthus’s essay strongly influenced the thinking of both Charles Darwin and Alfred Wallace who independently produced the theory of evolution. It was from Malthus that Darwin picked up the phrase ‘the struggle for existence.’ Discussing the fecundity of nature in The Origin of the Species (1859) Darwin wrote:
As more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species or with the individuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food and no prudential restraint from marriage. Although some species may be increasing more or less rapidly in numbers, all cannot do so for the world would not hold them.
The realisation of the struggle for existence led Darwin and Wallace to ask - in Wallace’s words now - “Why do some die and some live? And the answer was clearly that on the whole the best fitted live” (My Life 1905).
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