I don't think there is any breed of Modern horse today, that has not been linebred or inbred.
I think that over line breeding and in breeding will bring out less diserable traits as people no longer 'cull' the foals with problems and they get sold and some are bred..
Someone commented about people and inbreeding.. well Hitler would have, had the sick sob survived.
There's not breed of domestic animal that isn't the produce of in-breeding, line breeding or in-line breeding. How do people think man domesticated animals?
To over simplify the process
an animal that behaved less wild than the rest and was more accepting of humans or willing to be with humans or more willing to do what a person wanted was bred and then inbred with the offspring in the effort to create more that were like that. A trait was desired, found and bred for which would by necessity require that the original be bred to it's offspring that contained the same trait and the offspring of their offspring (and so on and so forth) as the domestic (dog, horse, cattle, sheep, goat, cat, chicken, duck, rabbit, etc, etc, etc,......) came into being. After domesticating them we then worked to "customize" them more defined traits by inbreeding, cross breeding, line breeding to create different "breeds" of a domestic animal (e.g. The Arabian horse, Friesian horse, Icelandic horse, Mastiff, Bloodhound, Border Collie).
Do people think that all these animals just "magically" appeared
. Humans have been doing this (obviously quite successfully) for longer than our recorded history.
As for passing on negative traits
, the Nazi had a solution for that which they did put into practice, but it wasn't inbreeding (anyone who had an undesirable trait was sterilized so it couldn't be passed on). This breeding solution was rejected by many. Of course for a most of human history in most societies those with obvious undesired conditions were openly culled by being left to die (if not killed) after birth (but I think the last of those ended in the 1800's....I hope
) Passing on negative traits is not unique to line breeding. In point of fact it's breeding outside a line that ultimately spreads many negative traits quicker to a greater number of whatever specie. If a trait only exists in a specific line then it's breeding outside that line that moves it into even more lines (that's true of every animal...including humans).
It's a two edged sword. To improve breeds (including people) you want to breed for more diversity so that the end product has more desirable traits to draw from (the best from each parent), but along with that we risk passing any or all negative traits from each parent. To maintain traits you need to breed to maintain that trait, but that limits the gene pool you can draw from. It all comes down to what you're wanting as your end product.
Ok class, be sure to read the rest of chapters 4-6. There will not be a test, but you are responsible for knowing the material