How did people make cheese before starters and innoculation?

I tried to research this for hours without much success.

Clearly people made all kinds of fermented dairy before we could innoculate milk with lab created bacterial colonies. I'm sure this means we had a long history of food poisoning, but truly...

...how was cheese (or any fermented dairy) developed before these industrial lab processes made our food safer and products more reliable??

Did you just leave it out to sour and add rennet? How could you ensure it was colonized by good bacteria, other than checking for "bad" mold growth?

Someone more educated than me...please enlighten me. Surely it's possible to make cheese without ordering a freeze dried packet of bacteria.