When it comes to synonyms for the phrase "act proverbially human," there are several that come to mind. One possible alternative is to "behave like a typical person." Another option could be to "exhibit typical human behavior." "Acting in a human manner" or "acting normally" could also be used. Additionally, the phrase "behave in a way that is characteristic of human nature" could convey a similar meaning. Overall, there are many ways to express the concept of acting like a typical human being, and which synonym to choose will depend on the context of the conversation or writing.