Try this little quiz testing your knowledge of the genetics of breeding:
1) What would you do if you wanted to increase the number of genetic diseases caused by recessive mutations in your breed?
2) What would you do if you wanted to reduce the size of the current gene pool?
3) What would you do to make a particular mutation "go viral" in your breed?
4) What would you do to reduce the effectiveness of the immune system?
5) What would you do if you wanted to increase the risk that a line of dogs or even a breed would go extinct just by chance because of the accidental loss of some critical gene?
1) Breed related dogs because they are most likely to have the same mutations.
2) Restrict the number of dogs that are bred so their genes don't get passed to the next generation.
3) Breed a dog that has that mutation as many times as possible, to get many copies of that gene into the offspring of the next generation.
4) Because the immune system requires high genetic heterogeneity to function properly, breed for homozygosity and lower genetic diversity by breeding related dogs generation after generation.
5) Keep the breeding population small by restricting breeding to just a fraction of the population and breeding as few dogs per litter as possible.
Well, how did you do?
In fact, we do all of these things, but for each we are trying to accomplish some "positive" goal (for example, to fix the traits we want by inbreeding or line breeding, get a bit of that popular sire into our own line, etc.). But we fail to consider the negative consequences that will also result. It doesn't matter how good a breeder you are, or how many years of experience you have, you can't gain the positives without also risking the negatives.
The high rate of genetic disorders in dogs is a direct and predictable consequence of the way we are breeding. There is no mystery to this, no difference of opinion among scientists, no bad luck involved. And it's not rocket science - you don't need a degree in genetics to understand why this is happening.
Unfortunately, the best way to get more of what we have is to keep doing what we're doing.
Check out ICB's online courses and our Breeding for the Future Facebook group