<p>Human brain organoids (hBOs) are being used as models for researching neurological disorders and testing for neurotoxicities and therapeutics. Proposed as ethical, more representative alternatives to human and animal experimentation, they must be as nearly like the original tissue source as possible to be convincing models. Yet being too near to living human brains resurrects long-unresolved uncertainties about humanness, moral status and cultural meanings around the brain. In this paper, I use Svendsen’s framework of nearness to examine tensions around hBOs as human brain-like substitutes. I illuminate ways scientists, ethicists and others employ material and discursive practices to construct hBOs as near-original or distinct from the original entities. By conceptualizing these as authentication practices, I focus on ways hBOs are made to matter as valid substitutes for the original. This provides a unique perspective from which to analyze novel life forms and their infrastructures.</p>