What do you mean? If you're talking about developing breeds of dogs, isn't it true that mutts are more robust? From time to time, I hear that certain breeds are susceptible to a particular health problem. But then, I'd never pay for a dog, when kids are standing outside Wal-Mart givin' em away.
Mutts are more robust when it comes to dog breeds but that is because in breeding dogs the breeders are looking to reinforce particular traits that identify a breed. They are not trying to reinforce positive genes and eliminate bad ones. In cattle breeding the same thing happens. When developing animals for meat those characteristics are reinforced. The breeder doesn't care whether that comes with a short life span, weak bones or not. They breed for one or two characteristics only. The inbreeding comes about because breeders can see the traits in just a few generations as opposed to the many it would take if they bred non-related animals.
From a genetic point of view the probability of reinforcing good traits when inbreeding occurs is only slightly less than the probability of reinforcing bad genes. In nature the problem is self correcting. In human society it is not as humans understandably have a reluctance to
throw away their offspring or just leave them to die. So carriers of bad genes unless the gene is fatal, go on to breed (hemophelia in the royal families of Europe, The elongated mishapen skulls of the pharohs(sp)).
The incest taboo makes perfect sense humans being what they are and pretty much must be enforced if our gene pool is to remain diversified (but only because humans are unwilling to take the steps necessary to eliminate those traits that are not so welcome).
Ideas like I've presented above led to the hole eugenics thing of the early to mid 20th century and we all know where that led. There's a reason inbreeding and selective breeding are taboo. In most cultures they create more bad than good.
