Good post Dan. I have a few thoughts I thought I might add if you don't mind. [quote=Astibus]Inheritance is not as straight forward as many believe. Oftentimes, people mention percentages of “blood” in their dogs as if these were absolute certainties, whereas in reality the percentages beyond the actual parents rather describe only probabilities.[/quote] It is this very reason that while some people have hounded me wanting to know percentage this or percentage that...I keep telling them you have to select for TRAITS. Yes, percentages can be close to probable outcomes...but the absolute outcome isn't fixed on a percentage. Instead, it is fixed upon the selection pressures of the desired features. [quote=Astibus]...recessive genes can be carried along without being frequently expressed nor completely eliminated from the gene pool; only to pop up, if and when they prove advantageous.[/quote] Yes, if the recessive genes are popular enough to recombine as a fairly common occurance in order to select for the phenotype expressed by a homozygous recessive genotype...and therefore increasing its breeding. If the recessive gene is rare though, then it will be extremely unlikely for this rarity ("endangered") to exist in a homozygous (expressed) recessive form and therefore a rare recessive gene may only exist in a heterozygous genetype carrier that would be phenotypically no different than a homozygous dominant genotype/phenotype...and therefore never be given any favoritism. If a heterozygous genotype expresses a phenotype that is more likely to survive than a homozygous dominant geneotype...then I might would agree with this as a liklihood, but if that was the case it really wouldn't be "recessive" but codominant or incompletely dominant. [blockquote]Why do breeders and dog owners experience problems more frequently in recent decades and not as severely in the early days of breeding for type? The answer to that is that “linebreeding” is only one half of the story, only one part of a truly successful strategy... ...only the fittest survive. Nature “recalls” those that didn’t make the cut – for whatever reason.[/blockquote] Agreed...In other words, performance selection. Breeders must remember this if they really expect to produce working quality dogs. Too many breeders say they breed for working ability, but in actually don't. Just look around. For example...I am not saying x-raying dogs and such is a bad thing, but to think that x-rays is some proof of working ability simply is an amazing ignorance IMO. In nature, the "x-ray" is...do you have what is needed to survive? Well, breeders should ask..."do you have what is needed to do the job you have been bred to do?" and then they should test the dogs accordingly with real tests that measure these working abilities. I have never heard of a winning alaskan musher sled team that placed x-rays, pre-lims, thyroid tests, etc over the ability to pull the sled...yet, remarkably working class huskies are fitter than show huskies...which inherit comparably good fitness from their working cousins when compared to predominantly show bred non-working breeds. Now of course, this arguement/point shouldn't be used to justify not x-raying a dog or doing other tests UNLESS the breeder is REALLY GOING TO PUSH A DOG to its limits, measure recover time, etc to realy look for maximum performing individuals within a population...and not confusing such feets as such with wishful thinking while running "fi-fi" or "fu-fu" around the block. One final comment on culling Culling doesn't have to mean death. It just has to mean removal from the breeding population. Culling can humainly be done by spaying or neutering an animal and placing such individuals in pet homes. OH...and here is a link to a similiar topic I posted on the Bandog discussion forum, that I probably should have posted in the general topic forum as it pertains to all breeders. http://www.molosserdogs.com/modules.php?name=Forums&file=viewtopic&t=2584