I don’t know that much about dogs, so this question popped in my mind and I can’t seem to find a good answer.
Will canine brothers and sisters readily interbreed if given the opportunity, and will the results of that breeding typically be defective in some way? This articleseems to say that there may be issues with interbreeding, but another way to look at it is that there may not be any health-related issues.
I know that human brothers and sisters interbreeding would generally not be a good thing for the offspring, I was just wondering if that’s a general rule with mammals or mostly just a human thing?
I use to hear different trains of thought on this from dog breeders. I was into pointing dogs for many years. Some breeders felt that inbreeding would quickly expose any genetic defects that could then be eliminated form the breeding program. Irresponsible inbreeding has been going on for a long time by dog breeders. The pups are often sold off before defects manifest themselves.
Inbreeding concentrates traits - both good ones and bad ones. In the hands of a knowledgeable breeder it can be an incredibly powerful tool, allowing the breeder to “double up” the most desirable genes while locating (and culling out) the nasty recessive traits in his lines that are normally hidden. But if carried on for too long, it can result in a decline in fertility and weakness of the stock. Eventually, an outcross to a different breeding line will be required to restore vigor.
And yes, canine siblings will readily interbreed. They don’t have an incest taboo.
As mentioned above, inbreeding concentrates both good and bad traits.
It’s a potential problem with cheetahs. They are so inbred, they are all very genetically similar. There are some benefits - they don’t seem to have many genetic diseases (or else they’d all have it). But a single contagious disease can also wipe out huge groups of them.
Excessive inbreeding also seems to be a factor in the spread of the Tasmanian devil’s transmissable face cancer. It appears to spread more quickly the more genetically similar the animals are.
We’ve also artificially done the same with mass-farmed pigs and other livestock. To maintain consistency in flavor and meat quantity, we inbreed pigs a lot. That produces genetic similarity. But it also means a single missed contagion can spread through all the pigs. Pigs grown the old fashioned way have fewer problems due to greater genetic diversity. Likewise, we inbreed cows to produce more milk. In such cases, we do have to cull the herd of undesirables.
Back to dogs, inbreeding is often used to generate dogs with specific traits - it’s often how we get new dog breeds. And, yes, it can be a problem. Here’s a relatively recent news article about some of the issues found in inbreeding dogs in Japan.
There’s some interbreeding in the early stages of reviving a nearly extinct breed. Most Portuguese Water Dogs come from a gene pool of about 15 dogs that were imported to the United States during the Portuguese revolution in the 1970s. There are issues resulting from a very small gene pool, such as the prevalence of otherwise rare diseases like hemangiosarcoma (which took down one of my two PWDs last month; the other died of complications related to another form of cancer a couple of weeks earlier) and Addison’s Disease.
PWD breeders today will try to pair dogs and bitches that are as far apart on the family tree as possible. There’s also a LOT of genetic testing, which is reflected in the cost of puppies.
On the other hand, when the products of inbreeding contract recessive genetic diseases, it’s rough on the individuals, but good for the gene pool as a whole. Those recessives matching up and getting eliminated is how the incidence of the genetic disease in the population decreases. Whether this is worth it or not depends on your opinion of the worth of individuals of a given species.
It’s a known problem with Northern Elephant Seals too. They were heavily hunted and thought to be extinct by 1890 or so. An expedition found a remnant of 8 individuals on Guadalupe Island in 1892. Cleverly, they killed 7 of them for their museum collections! :smack:
Apparently, there were a few more on the far side of the island that they missed. Stupid explorers. From that founder stock, the entire northern population that we see today was regenerated. To this day, the northern population is very heavily genetically bottlenecked.
Elephant seals look inbred. Cheetahs also had a big bottleneck.
Dogs will mate with siblings and with parents. My friend got an inbreed awhile back. You might think he’s retarded due to his behavior, but then it’s hard to tell as he’s a puppy. A puppy who can reach your face.
On the plus side, maybe they can claim the Hapsburg fortune.
Many breed-specific maladies are often attributed to inbreeding that occurred when that particular breed underwent a surge in popularity (e.g. collies, st. bernards, cocker spaniels, etc.).
Inbreeding is especially problematic if a breeder conceals that fact about their animals.