Population Genetics

Population genetics is the study of the allele frequency distribution and change under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. It also takes account of population subdivision and population structure in space. Thus it attempts to explain such phenomena as adaptation and speciation. Population genetics was a vital ingredient in the modern evolutionary synthesis. Its primary founders were Sewall Wright, J. B. S. Haldane and Ronald Fisher, who also laid the foundations for the related discipline of quantitative genetics.

Although the principles of population genetics were laid down by Wright, Haldane and Fisher early in the twentieth century, by and large the purebred dog world is still totally unaware of this aspect of genetic science. That long-continued ignorance has been disastrous for purebred dog breeds and has been largely the cause of the genetic "crisis in purebred dogs." Sustained, mindless inbreeding, assisted by high levels of cosmetic artificial selection, population bottlenecks, founder effect, and random genetic drift have stripped most of the original genetic diversity from registered dog breeds, leaving them with high levels of expression of genetic load in the form of recessive genetic diseases.