But how does your theory account for men with a robust skull and a gracile body?

Even limiting discussion to women only, if as you claim a Gentile woman did not hunt but ate meat, her husband probably hunted in order to supply her with the meat. Her husband would thus likely have a more robust body than her. If she had a daughter, the daughter would be expected to have a more robust body than her due to inheriting partially her husband's traits. How then could there be a steady multigenerational drift towards gracility under such conditions?
Why not use the simpler explanation of the robust skull and gracile body as a product of (disgusting) mixing of non-Aryan with Aryan blood?