Some faces have normals which are opposite of others. Along the lines seperating opposite normals, border edges develop, and these in turn aren't smoothed well by the smooth function.
To fix it I turned on normal display (found under display->polgon components->normal in MAYA) and clicked on all teh faces whose normals pointed inwards instead of outwards.
I then went to edit polygons->normals (it's way at the bottom) and reversed said normals.
The smoothing is perfect along that odd secondary ridge. The brow line still exists, but it's much less pronounced now. Here's a pic:
