What Is a Substitution Cost?
Charles Darwin's theory suggests that man and ape descended from a common ancestor over a period of five million years. John Burdon Sanderson Haldane, an author and genetics teacher at University College in London, supported Darwin's theory in principle but believed the theory lacked facts. He developed works based on "substitution cost," in which he discusses the effects of the environment and its role on genetics to support his beliefs.
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Background
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Creationists have debated Darwin's theory of evolution for decades. Haldane presented the theory of substitution cost in his 1957 research paper titled, "The Cost of Natural Selection," suggesting that, mathematically, genetic evolution from a common ancestor to man in five million years was not possible. He refers to inevitable deaths as a result of environmental changes to support his beliefs. He died in 1964, leaving behind works to re-examine Darwinism.
Environmental Factors
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Using the example of the population of a single species of animals, Haldane claims that changes in environmental factors might leave the majority of animals within a species fighting for survival. Due to genetic variation, some animals might be able to protect themselves. Animals with a genetic variation of longer fur could manage to survive in unseasonably lower temperatures. With each generation, the genetic variation increases to boost the new breed. In the meantime, however, deaths are inevitable. Haldane calls these deaths resulting from environmental changes, "substitution cost."
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Substitution Cost Theory
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Haldane's substitution cost, also known as the cost of natural selection, refers to the number of deaths required in a population for a substitution to occur. He believed that a substitution of 30, or deaths 30 times its population size, is typical for substitution to occur in a diploid organism -- referring to a cell with two sets of chromosomes, as carried in humans and most animals. In other words, it would take three million deaths in a human or animal population of 100,000 for substitution to occur.
Mathematical Theory
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Haldane believed that genes would not withstand changes of the environment and that the environment would increase the naturally occurring death rate. Haldane believed that deaths of 30 times the population size for the substitution would require 300 generations to fix a single gene. Therefore, the theory of the evolution from a common ape-man ancestor to man in a period of five million years was not plausible.
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