'Teleonomes in Tatters': The Welfare Costs of Selecting Dogs for Extreme Phenotypes, and the Case for Change.

The domestic dog is the most morphologically diverse domesticated mammalian species. That diversity has arisen from deliberate, sustained artificial selection over the most recent 1% of the domestic dog's evolutionary history. However, artificial selection has pushed many individual breeds so far from the ancestral canine form that many dogs within these breeds can no longer perform the critical biological functions their bodies evolved to serve. Indeed, much of the popularity of many dog breeds is predicated on them no longer being functional dogs; rather, they are representations or caricatures of human aesthetic desires. The result is breeds in which the teleonome of individual dogs, i.e., the integrated biological system by which they maintain viability has been structurally dismantled in the pursuit of appearance. This article applies teleonomic and allostatic load theory to a multi-domain analysis of extreme brachycephaly as a primary case study, drawing on representative examples from other extreme phenotypes to examine their welfare costs across conformational disorder, innate health, allostatic load, and veterinary costs. A detailed Five Domains analysis of extreme brachycephalic morphotypes, where the epidemiological evidence is most complete, reveals that every major welfare domain is simultaneously compromised from birth because artificial selection has structurally compromised teleonomic function across morphological, physiological, physical, and behavioural traits. Allostatic load theory then provides the mechanistic explanation for the resulting shorter lifespans. The article concludes by addressing the veterinarian's emerging role as arbiter of animals' fitness for purpose under consumer and welfare laws, making the case for an Innate Health Assessment to become a standardised functional assessment framework grounded in teleonomic principles.