It has long been said that the Beast Arts were granted to the beastmen by the gods at the time of creation. The elves were gifted long lives filled with beauty. The humans were granted adaptability and bountiful lands.
However, the beastmen were left to fight in barren lands and relied upon strength to survive the harsh world and one another. The gods took pity on their struggle and granted them Arts meant only for their kind.
At least, this was the story that was passed down from generation to generation. None could say if this were truth or fanciful fiction, but there remained one truth regardless of which it was. Beast Arts were something that only those who shared in a bounty of their blood could access.