Both Emacs Lisp and Common Lisp are coming from MIT's Maclisp dialect. There were Emacs variants written in Maclisp or its dialects before GNU Emacs existed. Em

Both Emacs Lisp and Common Lisp are coming from MIT's Maclisp dialect. There were Emacs variants written in Maclisp or its dialects before GNU Emacs existed. Emacs Lisp was a very simplified Maclisp. Common Lisp modernized Maclisp (especially lexical binding), preserved a lot of Maclisp features and standardized stuff like an Object System (CLOS), error-handling (Conditions), enhanced argument lists (especially keyword arguments). RMS especially did not like the addition of an object system, lexical binding as the default and keyword arguments. Those three things are quite central in Common Lisp. Emacs Lisp has no object-system in its core, lexical binding has only recently added and it has no keyword arguments. Scheme is quite different from both. But Guile is a very special Scheme dialect with lots of enhancements, which makes it as large as a Common Lisp implementation. I would expect that code sharing between Scheme implementations is more difficult than between Common Lisp implementations.