The genetic variation exhibited in microevolution was deliberately put in place by the creator in advance, and did not arise from mutation.
I. Incompatibility of the assertion with Biblical literalism
Since the kinds of creationists who tend to make this claim also tend to be Biblical literalists, it is worth pointing out that the claim cannot be true if the story of Noah's Flood is true. According to the Flood story, only two of each kind of creature (or at least of most kinds: there is disagreement between certain verses of Genesis) were taken onto Noah's boat, while God sent the rest to a watery grave. Since individual organisms can have at most two alleles for each gene locus (we are excluding plants and assuming that Noah did not have Klinefelter syndrome), this means that each surviving kind of organism could have at most four alleles after the Flood, regardless of how many alleles were created by God in the beginning. But we now see far more alleles per locus for many loci in the populations of most organisms, which means they could only have come into existence by mutation.
In fact, the creationist claim is even incompatible with the story of Adam and Eve. Adam and Eve could at best hold four alleles per locus in their combined genome. But, as a typical example, locus HLA-DRB1 (one of the genes in the human leukocyte antigen complex) has 59 alleles (Ayala et al. 1993:78). If all humans are descended from Adam and Eve, at least 55 of these alleles must have been generated by mutation in their progeny.
II. Experimental refutation of assertion
More importantly from a scientific standpoint, experimentation with bacteria has shown that (for instance) antibiotic resistance can and does arise from beneficial mutation rather than being already present in the bacteria. Douglas Futuyma explains:
Joshua Lederberg did an experiment in which he grew thousands of colonies of genetically identical bacteria from a single bacterial cell that was unable to survive in the presence of streptomycin. He divided each colony of cells in two, and grew one half with and one half without streptomycin. A few of the colonies survived on streptomycin, because they carried new mutations for streptomycin resistance. (Futuyma 1983:137)
Since the bacterium from which the resistant colonies evolved was not itself streptomycin resistant, Lederberg's experiment proves that such resistance is the result of one or more mutations.
Ayala FJ et al. 1993. MHC polymorphism and human origins. Scientific American 269(6):78-83.
Futuyma DJ. 1983. Science on Trial: The Case for Evolution. New York: Pantheon.
Last updated: 3 Jul 2015
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