If you spend any time in this argument, one study comes up more than any other. Bannasch and colleagues, 2021: 49,378 dogs across 227 breeds, with a mean coefficient of inbreeding of about 25%. It is a serious piece of work on a large dataset, and it gets quoted at purebred dogs like a closing statement.
We think people should read it, because it contains a paragraph nobody quotes.
The breeds with the lowest inbreeding in that dataset were breeds with a particular history: landrace populations, and breeds that had been deliberately outcrossed. The Danish-Swedish Farmdog is the example worth sitting with — a recognisable, consistent breed, with a gene pool that was never narrowed to the point of damage. Breed type and genetic diversity are not opposites. You can have a dog that reliably looks and behaves like its breed without closing the door on its population.
Read that way, the finding is not an argument against breeding dogs on purpose. It is an argument against appearance-first selection inside a closed population — against choosing a narrow set of winning dogs, using them heavily, and letting the gene pool contract around them. That is a real failure mode and it has real victims, and preservation breeders are among the people who talk about it most, because they are the ones who have to live inside the consequences.
What good breeders do with this information is unglamorous and specific. They calculate coefficients before planning a pairing instead of after. They use population-genetics tools. They look at the whole breed’s diversity rather than one litter’s. Some of them, in some breeds, argue for opening the stud book — and in at least one breed, they have actually done it. The Irish Wolfhound is a documented reconstruction built on deliberate outcrossing, and it is still here.
The study is not the other side’s trump card. It is a description of a problem that the most careful breeders were already working on, and it tells you which direction to work in.
Sources
- Bannasch D. et al. (2021) — inbreeding across 49,378 dogs and 227 breeds; mean COI approximately 25%. Source paper re-verified 17 August 2026.