The breeder of domestic stock often assumes that he has abandoned the realm of natural selection and that only artificial selection plays a significant role in his breeding programme. Nothing could be further from the truth. The breeder may attempt to abandon natural selection; natural selection, however, will not abandon his stock. As one geneticist puts it:
Those who attempt to set aside the balanced genomes arrived at by natural selection must struggle thereafter to attain and to maintain fitness in their stock. There is more to this than mouthing platitudes about "soundness." Artificial selection alone, such as that used to produce winning exhibition dogs, involves breeding in a way which flagrantly disregards most of the gene loci in the canine genome. Since genes assort in groups on chromosomes (a phenomenon known as "linkage"), inbreeding and selection for desired traits of superficial appearance unavoidably affect many other genes which are inadvertently selected and often fixed in a homozygous state in total ignorance of what is happening. This may be a major factor in the current prevalence of genetic diseases. Thus natural selection, baulked for a season by artificial selection, high-level nutrition, and advanced veterinary care, reasserts its primacy at a deeper and more serious level when the new genome as set up by the breeder proves flawed through genetic unsoundness, so that healthy and hardy animals can no longer be produced, however typey and attractive to the eyes of the judges the result may be.
Declining vigour caused by the inadvertent fixation of sublethal and subvital alleles will not be made up for by breed points. Fitness criteria may not be replaced with impunity by aesthetic criteria. The animal's environment is the ultimate arbiter of its fitness and will not be denied its say. You may vaccinate the dog and dose him with antibiotics, feed him with vitamins and minerals as you like, enclose him in a sterile pathogen-free laboratory environment if it comes to that! Still natural selection may not be avoided; it only emerges at a deeper level. In a sense the dog's environment includes his own physical body; if the genes which blueprint his physiology are flawed, then the dog is doomed regardless of his beauty and classic breed type. The truth is that the "superior strain" cannot be produced by manmade breeding programmes and artificial selection; the breeder's decisions are subject to nature's veto at all times.
With what, then, will the breeder replace natural selection? If he replaces it with profit, the degeneracy of his stock will in the end put him out of business as veterinary costs and death eat up his profit margin. If he replaces it with beauty contests, in the end his beautiful contest winners will engender weaklings and degenerates. If he replaces it with screening programmes for the "elimination of genetic defects," in the end his stock will succumb to inbreeding depression as bitches fail to whelp naturally and puppies die in the nest. If he replaces it with veterinary care, in the end his stock will die prematurely of incurable cancer, or the young will fall prey to viral diseases despite repeated polyvalent vaccinations. If he replaces it with work and austerity, his stock may endure awhile longer, but in the end it will turn out to be afflicted with genetic ills that slipped through his demanding programme, or its performance will mysteriously decline as the inbreeding coefficient creeps upward. In the end, natural selection cannot truly be replaced with artificial criteria. The breeder must find a way to work with natural selection, within the framework of what is now known about the biological operation of the natural world. We in the canine fancy must begin to take lessons from wildlife biologists, from evolutionary biologists, from population geneticists.
In our quest for breed purity, the superior strain, and classic type, we have made a sad mess of our dogs -- with unhappy, neurotic temperaments, epilepsy, blindness, deafness, immune system weakness, skin diseases, blood disorders, endocrine system malfunctions, crippling bone disorders, deliberate deformity, and often even the inability to reproduce their kind without breeder and veterinary intervention. How clever we have been!
Can we not now take a clear-sighted view, as the millennium turns slowly over, of what we have done -- of our own pitifully-flawed creation in our world of purebred dogs and, like mature, intelligent people, clear away the mess and try to do better? Can we not learn from bad experience? If we would be truly clever, we might attempt to imitate more closely the methods of nature, to work within the natural system, albeit for our own ends. That would indeed be clever. I think that that is now possible, if we would but step outside our own incestuous little purebred world and learn something of what people working in other zoological fields of endeavour have already learnt.