Originally Posted by nonnieyrissa
Yeah, I couldn't find the exact words to explain what I meant.That is a part of what I meant.But there was more. To evolve means the development of new species or new traits within a species over a time right? So they are losing to some degree the ability to completely care for themselves, varying depending on what they have been bred for. Even breeding a sheep for longer hair would make it more likely for them to develop giant "rats nests" in their hair which can cause sores, which if not cared for can become infected, which could move into their blood stream and be fatal.
I understand where you are going with the explanation, but the key here is humans. While an animal is domesticated, those traits such as longer wool are adaptive; they result in a reproductive advantage for the animal under the conditions in which it lives. If conditions changed those traits could become maladaptive, but that is true for any trait to start with. The "fitness" that evolution produces works only under a very specific set of circumstances. Change the circumstances and what makes an organism "fit" could make it very much "unfit" for the new conditions.
As an example, I will use polar bears and their fur. While they live in an area dominated by cold and snow that super-insulating hair is a very good thing, and makes their lives possible. If the climate warms (whether changed by humans or by normal cycles is irrelevant) then that hair traps too much heat, and can in fact kill them. The hair is neither a good or a bad trait in and of itself, indeed no trait is good or bad in and of itself. Conditions can change and make any trait good or bad for the organism, regardless of whether it worked in the past.
And by the standards of evolution, domestication has been very good for the animals we chose. Cows could never have achieved the numbers they have now had their wagon not been hitched to ours. It is entirely possible that had we not domesticated a given animal that species may have died out, as so many others have. It is possible that once humans are gone and conditions change for the animals they will die out anyway because of the changes we have made, but that is true for any animal that specializes.