It would seem that some breeds of dogs are so inbred that genetic defects are becoming a major problem, and are in fact leading to great suffering for the dogs. A related study by scientists at Imperial College London has shown that the 20,000 strong population of Boxer dogs has the genetic information of only 70 animals, the 12,000 Rough Collie’s contain the genetic information of only 50 dogs. See also:
Calboli FC , Sampson J, Fretwell N, Balding DJ, "Population structure and inbreeding from pedigree analysis of purebred dogs," Genetics, 179(1): 593–601, 2008. doi:10.1534/genetics.107.084954
Two observations come out of this. Firstly, a great deal of morphological change can occur in a short period of time and yet not turn a dog into something that isn’t a dog. Changes in size, shape, colouration etc. occur, but still they are dogs, while the gene pool becomes ever more focussed on a few individuals. Large changes can occur by isolating and expressing pre-existing genetic information in a species without generating new information.
Secondly, the compounding of harmful mutations is a major problem for inbreeding in small populations in the wild, so much so that it risks the viability of the breed / species itself. The problems association with the tumours on the faces of Tasmanian Devils is a case in point. And yet evolutionists will say that such small inbreeding populations have been an important part of the evolutionary process. The evidence suggests a different account, as it would constantly place evolving animals on the edge of extinction. Evolutionists will of course claim that artificial selection is not the same as natural selection because natural selection will weed out the unfit animals whereas human breeders don’t. But even that doesn’t help much as Haldane’s paradox highlights. Beneficial mutations are much rarer than harmful ones, and are more likely to be found in very large populations. But small, or isolated populations are required to get those mutations to spread through a population. The speed at which mutations become fixed in a population must also be sufficiently slow to weed out the far more numerous harmful mutations. Evolution then would require at the same time the benefit of very large populations and very small ones - without the overwhelmingly observed side effects that develop from compounding harmful mutation in small populations. Thus the gene pool of large populations cannot change much at all over time; while the gene pool of very small inbreeding populations in fact degrades making the species less fit overall.
It’s worth reading the Question Darwin blog for a more complete review of the evidence presented in the programme. Question Darwin Blog - Pedigree dogs, Genetic Entropy and Denial
Some video clips are available on the BBC website.
Video clip 1
Video clip 2
Video clip 3