Hi, malted corn will actually make it's own yeast. My grand dad use to make corn likker and never used store bought yeast, and he was'nt alone in doing that. A lot of purists still make it in that manner. I personally think the likker produced in this manner has a much harsher taste than when made with distillers or bakers yeast. As to the hangover aspect, if you drink to much of the heads and/or tails then a hangover will occur.
Alcohol has been made for centuries with many different ingredients without adding yeast to the wurts. the first wine fermentations, and some today, were fermented with the yeast on the grape skins.
You can neither create nor destroy matter---only transform it.