(Spoilers Extended) Origin of Valyrians

So, it occurred to me that dragonbinder might be the key to explaining how the Valyrians attained dragons. They were all shepherds before, and it makes sense that they'd use a sheep horn to call all the animals in. What if some shepherd found a dead dragon with a horn, etched some runes in the side and then used that to bind dragons to their bloodline. Not the most original theory for sure but I wanted to see what other people here think.