The first is soaking, especially marinating. Vinegar forms naturally. So does saliva, sometimes used for marinating.

The second process is also universal–decomposition (sometimes call rotting or even putrification, or more positively–aging). Many cultures still use various forms of decomposition for vegetables, fruits, fish, and red meat. Fermentation, of course, is also a form of decomposition that then yields one of two preservatives–vinegar or alcohol. Early humans would certainly have learned to use marinating and decomposition or aging long before they became adept at cooking.