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Darwin and the Wedgwood’s: The Cost of Inbreeding

Jonathan Leake, writing in the Timesonline [1], reports on the latest research by James Moore of the Open University. This shows that the frequency of infertility, miscarriages and illnesses in Darwin’s family may have been due to successive marriages between cousins.

Darwin in fact married his first cousin Emma Wedgwood (of the famous pottery firm) and both his maternal grandmothers were Wedgwood as was his mother Susannah Wedgwood who married her cousin Robert Darwin. The Wedgwood family wealth also provided Charles with the financial resources to become a gentleman of leisure able to pursue his own scientific interests and projects.

Charles and his wife Emma had 10 children in all. Three of his children died in childhood, and three were infertile in later life. Michael Golubovsky, who is a Professor of molecular biology at the University of California in Berkeley, agrees that the close breeding rendered the Wedgwood and Darwin families partially infertile, and that a mutant gene was probably the cause. Through close family breeding such mutant genes become compounded and expressed frequently.

Moore also believes that Darwin had in fact been concerned that he had passed on his own illness to his beloved daughter Annie. Some of the other Darwin offspring came down with similar symptoms to Charles.

This sad evidence does of course raise questions about the efficacy of Darwinian explanations that require close breeding in order for evolution to work. Animals such as the Tasmanian Devil seem subject to genetic weakness (in their case it is facial tumours) and this is possibly due to inbreeding on the island.

Summary

Neo-Darwinism in fact requires small inbreeding populations in order to get beneficial mutant genes to spread through the whole population, but the evidence reveals that this cannot work. Beneficial mutations, if they exist at all, are very rare and are more likely to be found in very large populations. So small inbreeding populations are very likely to compound harmful mutations and are very unlikely to find beneficial mutations. Such species are therefore often found on the verge of extinction in the wild. On the other hand mutant genes cannot pass through large populations in anything like the time needed for evolution to occur in the time frame given in the standard evolutionary model. This problem has been described as Haldane’s paradox. Haldane calculated that higher vertebrates cannot pay the cost of evolving in terms of speed of breeding, higher birth rates, and the need to remove the non-mutant forms from the gene pool. What we can see then is that large populations resist evolution and the spread of novel mutant genes through the population, and survival of the fittest tends to ensure the quality of the existing gene pool. While on the other hand small populations are often found on the verge of extinction because of the problem of compounding harmful mutant genes. Either way the neo-Darwinian synthesis seems to be caught on the horns of a dilemma.

[1] Jonathan Leake, Unnatural selection: Darwin’s family damaged by inbreeding, Timesonline, 2nd May 2010 http://www.timesonline.co.uk/tol/news/science/genetics/article7114113.ece#cid=OTC-RSS&attr=797084

This message was added on Tuesday 11th May 2010