Emacs source code goes quite far back, with extensive changelog between every 2 functions, if you don't fancy rifling through commit log itself: https://git.savannah.gnu.org/cgit/emacs.git/log/

Earliest commit is from 1985: https://git.savannah.gnu.org/cgit/emacs.git/commit/?h=emacs-...

Log starting from 1985: https://git.savannah.gnu.org/cgit/emacs.git/log/?h=emacs-19....