Introducing the trope (Un)Becoming Old, the thesis examines the processes by which biomedical inquiries and (re)definitions of aging are increasingly enmeshed with longstanding ontological debates over the static or processual nature of ‘being.’ Following ethnographic networks of scientists, advocates, and entrepreneurs seeking to slow, halt, or reverse aging, it looks at intersections of philosophy, science, capital, and culture that inform efforts to extend human ‘healthspan’ and lifespan—in turn showing that aging has become a major site of value extraction by a speculative sociotechnical system. The ethnographic material is situated against a backdrop of processual concepts popularized by the Presocratics onwards, which are then integrated with critical readings of biological literature and the latest in aging research. Through its tripartite exploration of (Un)Becoming Disease(d) (an emerging aging-as-disease campaign) and (Un)Becoming Human (a techno-utopian take on teleological and alchemical relics), (Un)Becoming Old problematizes normative notions of progress, transcendence, and humanity that undergird the broader geroscientific project. The thesis shows that processual biology, anthropology’s ‘ontological turn,’ and parallel developments in other fields reveal a contemporary re-emergence of (early) ontology as the fundamental question in scientific inquiry. By anthropologically engaging the science of aging along with the broader implications of a processual approach, the thesis lays the groundwork for a novel understanding of senescence as a bio-experiential-social process—whereby sociocultural contexts shift biological processes of aging and vice-versa.