What does dogs mating with horses have to do with evolution?
Why should common origin = being able to reproduce? They have diverged a lot from their common origin. Different "types" have evolved to fill different niches.
"Types" and "kinds" are arbitrary designations.
This is what I am saying is inaccurate, and I believe OrionzRevenge is correct is saying that we probably will not come to agreement.
The origin of species suggests that species originated from a common ancestor.
Although the theory is widely accepted by academia, it is still muddled and confused by purely scientific standards of today. Yes, as smart as academia, science, technology, and medicine is, they are all confused because they lump together natural selection with evolution, which is the key mechanism to many of these fields as well as evolution. However, the two are suggesting very different things. Natural selection is well known to be real and observable, but to infer evolution from it is a jump far past the imaginary magnitude of Creationism.
Producing better versions of the same thing will never produce something entirely different. It will only produce varying, as you say, niches. The question here is, if you go back far enough, would there be a common origin, and the niches, over so many million years, able to eventually produce all the species we have today. Evolutionists say yes, down to the very basic building block of life, carbon (rock). In other words, we all came from rock. Rock is our common origin because it's totally comprised of the element that is the building block of our life. Not saying this is stupid at this point, but anyways this is the logic and for the most part we can make sense of this, no?
Creationists say no, because the kinds of animals were made by God and they did not form themselves. Within each kind, they can "bring forth" more, i.e. reproduce, which is why dogs and horses can't be bred, but zebras and horses can, and dogs and wolves can, because they are the same kind. They are made from carbon because it is the same material used for a lot of the universe, another sign of a single designer.
Now, think about the similarities. I vehemently disagree that the two theories can agree (I used to think this but now understand that they simply are not compatible). Both ways are, though, interpretations of a single pattern of reality, and that reality is origin... evolution says the single origin does not include God, the origin is the material itself which spontaneously lived, similarly to how the universe spontaneously existed, The only way this is even remotely possible (and I am talking remotely, like 1 in 10^928 remotely) is with millions or billions of years, until the carbon randomly generates sustained life. A common analogy for this is an infinite number of monkeys banging on an infinite number of typewriters, one would eventually write Shakespeare. And we don't immediately throw this out because we're here and conscious, it means we were fatefully the results of the Shakespeare monkey. This single origin explains the similarities and patterns of the kinds of animals and genetics. I'm not sure how it explains why different types of animals can't breed because according to evolution, they're all ultimately one type (carbon), but there are enough loopholes to cover that. Creationism addresses the same patterns of origin, saying that these obvious similarities and patterns to life clearly point to an intelligent designer. The analogy for this is finding a pocketwatch on the ground... it works together, it would be common sense to know that it was put together by someone because a bunch of matter isn't just flying around chaotically. Evolution says, you found the watch because you were the lucky one, and it simply was there because the infinity-minus-one other times it wasn't, and that everything organizes itself by the same metric infinity-minus-one (why our present reality continues to function the way it does without disintegrating back into chaos must mean that we're fatefully selected to organization.)
This is why evolution theory requires natural selection and billions of years in the lab that is the universe to cultivate life as we know it. However, it's a gigantic fallacy to say that the two are the same, and because natural selection is a vital mechanism to modern science and medicine, that it makes sense that the academic community embraces evolution.
Evidence pro-evolution is greatly grasping at straws. We have a few monkey and dinosaur skeletons that we line up and say that's the way it went, even though the paper thin method of carbon or argon dating don't hold up and the sedimentary layer method of forming a timeline of events was thrown out the window as soon as they found single trees that supposedly transcended time and space because they grew up through millions of years of fossil records.
So as you can see, both are explanations of the same pattern, it's just that one fits and one doesn't. Neither are based on observable evidence, as far as you're concerned, but why natural selection is linked to the (IMO) dead theory of evolution is a better question, why? Because we can't accept the notion that God's existence hypothetically begets everything science wants to discover?