"Most quaternary" can be replaced with a variety of synonyms, depending on the context in which it is being used. These could include terms such as "recent," "contemporary," "modern," and "current" to refer to events or developments that have occurred in the recent past. Alternatively, if referring to geological periods, synonyms could include "Holocene," "Anthropocene," or "Neogene." In a more general sense, other synonyms could include "prevailing," "dominant," "primary," or "paramount," all of which suggest something that is of utmost importance or influence. Ultimately, the choice of synonym will depend on the precise meaning intended and the audience for whom the writing is intended.