Trog

A sympathetic anthropologist uses drugs and surgery to try to communicate with a primitive troglodyte who is found living in a local cave.
Anthropologist Dr. Brockton unearths a primitive troglodyte -- an Ice Age "missing link": half-caveman, half-ape -- in a local cave. Through medical experimentation, she manages to communicate with him and domesticate him before he's let loose by an irate land developer and goes on a rampage, terrorizing the local citizenry.