Join Date: Feb 2012
Location: Alberta, Canada
I think it requires a lot of research to do correctly. Species that have not been extremely isolated or selectively bred tend to have very diverse gene pools. Small, isolated populations and selectively bred ones have smaller gene pools to choose from.
For example, two friends of mine are not related, but came from similar areas. They decided to have a baby, and discovered that the baby has a genetic disease. They were both healthy, with no real defects in either family, but carrying the same recessive gene. I know two families like this. I believe for hundreds of years, many populations were fairly isolated, by location, tradition or prejudice. It was traditional in many populations(English, French, Egyptian, to name a few) for close relatives, even siblings to marry. Where as before, most people, and especially the poor, would loose babies and children that had the slightest defect to disease, now many children have moderate to severe defects that would never survive birth or infancy, and are growing up to produce children of their own. There is no 'culling' in our species.
Similarly with horses, people are in breeding and line breeding for specific traits, and loosing sight of the larger picture, as a previous poster mentioned with the ear example. The gene pool gets smaller, the genetic defects get more concentrated, and more often than not, the soundness, health, sanity and well being of the horse are forgotten for the beautiful, colorful or talented. Even if a foal is born defective, people loose sight of breeding for the best possible off spring and breed crazy, poorly conformed or genetically unsound horses because they find the beautiful, they are attached to them or want their own foal. Culling is not done NEARLY enough in the equine world.
I have no problem with line breeding, done carefully by a very experienced breeder, but more often than not I disagree with it. I have seen thoroughbreds that are so fragile conformationally that they barely last till 2 or 3 without breaking down, but while they did run, they were brilliant. One mare I knew personally had the same stallion 6 times in the first 4 generations of her pedigree. She was so fragile mentally and physically that she had no practical use, other than to be a brood mare.