This Element introduces the study of Deep Time Heritage as a new field of critical global research. It applies a critical heritage perspective to the archaeology of the Pliocene, Pleistocene and earlier Holocene as it engages with data and interpretations on so-called hunting/gathering/fishing societies. Using a range of case studies, debates and key topics, the Element explores different processes, negotiations, and contestations through which these forms of archaeological and palaeoanthropological research are transformed into contemporary heritage. It argues that this past is 'keystone heritage' and disproportionally shapes conversations on both present and future. It thus advocates for greater critical reflexivity in the study of humanity's deep past and its construction in the present and - in this context - a greater awareness of the importance of the intersection between archaeological knowledge production and public and political discourses.