Breathe
Hostis humani generis
You're making the mistaken view of them coming from something different; while it is true this happens when you take a million or so years out of the equation, they happen slowly: the animal which becomes 'something else' changes so slowly that the animal isn't very different from its great-grandparents.So basically you are saying we all share a common ancestor, meaning that every animal (human included) that is alive today gets its origins from something different than what they are....thus, in order for animals to arrive at their present state, they had to come from animals that were different from what they are. You don't see the religion in that? The faith it takes? If that isn't voodoo science, I don't know what is.
Traits are passed on genetically. You inherit characteristics from your ancestors; we all know that, right?
And sometimes these characteristics can mutate, such as a kid not getting his dad's baldness. It's not a massive change, right?
And if you go to live in a warm nation and you're fair-skinned, your skin will tan. After a few hundred years, your great-great-great grandchildren would be born tanned. Easy enough, right?
Now, if we get a giraffe with a shorter neck, it can't eat as much food as the one with the longer neck. So this one is disadvantageous. This one is losing in competition for food from other giraffes with longer necks. This giraffe may die out because it can starve to death, yes?
What if this short-necked giraffe finds another way to find food? For example, it starts eating from small shrubs because of its short neck. It doesn't need to have a long neck to keep eating the low-lying shrubs, does it? It won't need a long neck to feast on shrubs, so it won't be picked by females because of its neck. The mutation for longer necks isn't necessary; this gene will eventually die out in the short-necked giraffes; it's unnecessary, possibly even a hindrance.
Because of its shorter neck, it can't see predators as well, so it has to be faster at running. The slower ones die out because they're eaten. Nothing difficult here, right? Maybe it perks its ears up when feeding to listen out for predators.
Eventually, his great-great-great-descendants will be better runners, probably with more muscular legs more suitable for running, because they're the strongest. At the same time, its ears may permanently be perked up to listen, or possibly even able to move direction to listen to sounds behind them.
Now, imagine two crocodiles. One is white, one is green. The green one is harder to spot in the water due to his dark colouring. The white one is easier to spot. He finds less food, so he dies out, or at least is less successful in numbers than the green croc.
Nothing crazy here, right?
Tiny, almost insignificant mutations plus extremely long periods of time. Evolution isn't a religion, it's an inevitability. I know it's complex, though, so it can be difficult to accept, when there's a "simpler" explanation -- but that "simpler" explanation doesn't necessarily mean it's the right one, especially in the face of overwhelming evidence and odds.I know, it takes so long that it didn't happen.
We have a few biologists here; I really do suggest you speak to them in more detail. I'm just a layman in terms of evolution, I haven't studied it in any depth. They could explain it much better than I could, and probably clear up any misconceptions you may have (and fix any mistakes I may have made), so I really would suggest it.