Clarification of this for those interested in history: The original Mac did not have control keys; I guess NextStep had some Emacs bindings. When Mac OS and NextStep gave birth to Mac OS X, it was possible to keep both sets, as there could not be clashes. I am not sure those Emacs bindings 'officially' exist, though (the human interface guidelines mention the use of the control key for accessibility, but not for text editing)