This paper discusses the signification of the unreal in human language from an evolutionary perspective with the aid of recent research on language evolution across distinct but interrelated fields. The term ‘unreal’ is used here to refer to situations or entities that are not—yet—true or existing and in linguistic terms it relates to the notion of nonveridicality (Giannakidou 1998, Giannakidou Mari 2021), which is an analysis of the pretheoretical notion of the irrealis. From a biological perspective the role of the lateral prefrontal cortex is here highlighted regarding the signification of the unreal. In particular the function of prefrontal synthesis (PFS), defined in Vyshedskiy (2019) as the ‘conscious, purposeful process of synthesizing novel mental images from two or more objects stored in memory’