org-babel-load-languages

org-babel-load-languages is a variable defined in `org.el'.
Its value is

((emacs-lisp . t))

Documentation:
Languages which can be evaluated in Org-mode buffers.
This list can be used to load support for any of the languages
below, note that each language will depend on a different set of
system executables and/or Emacs modes. When a language is
"loaded", then code blocks in that language can be evaluated
with `org-babel-execute-src-block' bound by default to C-c
C-c (note the `org-babel-no-eval-on-ctrl-c-ctrl-c' variable can
be set to remove code block evaluation from the C-c C-c
keybinding. By default only Emacs Lisp (which has no
requirements) is loaded.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.