The Bone Crushers figured out how to artificially ferment flesh, avoiding mass starvation. Their civilization continued to advance, and inevitably their bodies began to adapt to its environment. With their food being partly processed for them, their powerful beaks shrunk, and the decline of inter- and in-group violence over sustenance caused their bodies to become more and more gracile as well. (The origin author is vanga-vangog in deviantart)