Psychology is the study of the mind. "Sociobiology" or "evolutionary psychology" (the latter was just supposed to be a PC term for the former) is the study of how and why the mind evolved--so, you see, it's a pretty broad term. How we came to have such a sophisticated capacity for language is a question of great interest to EPers, most of whom would agree with Chomsky.
"Does SB address the anatomy of, say, the human hand?"
No, because it's of very indirect relevance (if it's relevant at all) to the brain or behavior. Evolutionary biologists are interested in the question--ev psych is just the subdivision of ev bio that focuses on the mind and behavior.
-- Luke