Well, they didn't create corn (maize) so much as interaction with humans shaped corn's evolution via natural selection. Domestication is an evolutionary process. This answer by /u/YossarianWWII sheds some light on the subject. Farther down the thread they answer some question from me on the subject.

Hopefully that will hold you until someone provides a more specific answer.

That is truly fascinating. Thank you for that information. I would have assumed nore direct human intervention but natural selection makes perfect sense in its own way.