Sunday, June 29, 2014

Beneficial Gene Duplication

I have noticed a number of creationists bringing up this creationist drivel:

No known mutation has ever produced a form of life having greater complexity and viability than its ancestors.

If true, this would indeed be a notable objection, since in the evolution from single-celled organisms to homo sapiens surely some increase in complexity happened along the way. Evolution requires genetic changes that increase genetic information, and at least some of these changes need to be beneficial so that they are chosen by natural selection. What sort of mutation could do that?

Answer: gene duplications. Gene duplications allow for an increase in genetic information, and science has observed beneficial gene duplications in real life. From Evolution after Gene Duplication:

The beneficial impact of gene duplication has been shown for several classes of genes. Perhaps the clearest example of an adaptive increase of gene dosage through a gene is that of the amylase gene in humans. Amylase is secreted in the pancreas and saliva, and it starts digestion in the course of chewing food with a significant portion of starch hydrolysis occurring before food reaches the stomach….the number of copies of the amylase gene was found to be significantly larger among populations with a high-starch diet. In addition, the frequency of individuals with more than six copies was two times higher in high-starch diet populations. Most important, there is a clear interdependence between the number of gene copies and the amount of amylase in saliva.[1]

This is a beneficial gene duplication in human beings. The book also says that, “insecticide resistance through gene duplication has been recognized as a major force by many others”[2] though to avoid giving a false impression I should also quote them saying that an “important aspect of insecticide resistance through gene duplication is that at least some of these duplications are actually deleterious in an environment without the pesticide.”[3] Sometimes in evolution it’s a “you win some, you lose some” sort of situation. A mutation that is on the whole beneficial for the environment you’re in might still come at a price, such as the loss of some beneficial traits. That’s why the theory of evolution isn’t necessarily committed to us retaining all the beneficial traits of our ancestors, such as superior physical strength akin to apes.


[1] Katharina Dittmar and David Liberles Evolution after Gene Duplication (Wiley-Blackwell, 2010) pp. 63-64.

[2] Katharina Dittmar and David Liberles Evolution after Gene Duplication (Wiley-Blackwell, 2010) p. 64

[3] Ibid.

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