I am DEFINITELY not an expert on this, but I will give it a shot.
The reason for this is called the founder effect. This is when random changes in the gene pool that occurs in a new, small colony…genetic makeup of individuals can have a disproportionate influence on future gene pool. Basically what you are doing is taking genetic variation out of the gene pool. Healthy population have a large percentage of variation (if I remember right 12-30%). When you start with a small number the animals, the variation drops. You will see genes, that where almost nonexistent in large populations (because the had a negative effect), show up more often.
This is a common problem in endangered animals. Cheetahs suffered a bottleneck at the last ice age… only 3 populations exist today and they are all endangered and have low variability (.04% to 1.4% heterozygosis of alleles for individuals).
Northern Elephant seals reduced to 20 individuals in 1890’s… protected and now over 30,000 individuals…BUT out of 24 genes tested… no variation… single allele for each gene. This is a major problem.
It can also happen to humans, according to wikipidea..."For example, the Amish populations in the United States, which have grown from a very few founders but have not recruited newcomers, and tend to marry within the community, exhibit founder effects. Though still rare absolutely, phenomena such as polydactyl (extra fingers and toes, a symptom of Ellis-van Creveld syndrome) are more common in Amish communities than in the US population at large."
When you start a colony with a few boas, and the more inbreed they get the less variability. You will see genes that didn't have an effect on large populations pop up because they were naturally breed out (genetic drift). The animals will be more susceptible to disease, illness, and are less likely to reproduce.
I am not AT ALL against morphs. There are some awesome animals out there. But, when a new morph does pop up, I feel that it is the moral obligation of that individual to make sure the animals are outbreed as much as possible, and not to inbreed the hell out of them for the quick buck.
The bad thing is this is only going to get worse, as people try to produce animals with the most traits, and try to beat everyone else to it. That is not the answer...
Anyways, hopefully I will not get burned for this LOL. I just thought I would try to share more of a SCIENTIFIC approach to why boas such as snows have the potential to show more problems.
Search the net for founder/bottleneck effect and I a sure you will find tons more info out there.
-Kemper
recycle your pets