Manipulating Embryogenesis and Testing for Potential: Two Real Problems for the Regulation of Stem Cell-based Embryo Models

Stem cell-based human embryo models (SCBEMs), generated in vitro from stem cells, currently exist outside the scope of regulatory frameworks that govern in vitro embryo research in most jurisdictions. A widely discussed proposal suggests using a "Turing test" framework, whereby regulatory oversight is triggered if a SCBEM is found to be “equivalent” to a human embryo. In this paper, we argue that such a proposal faces two major complications. First, sophisticated laboratory techniques such as trophoblast replacement allow researchers to manipulate normal embryogenesis, obscuring whether a given SCBEM meets embryo-like thresholds. Second, attempts to assess SCBEMs’ developmental potential—especially through non-human analogues—rest on tenuous epistemic assumptions that may not align with human-specific developmental trajectories. Given SCBEMs’ potential manipulability and uncertain biological and potentiality benchmarks, we argue that reliance on equivalence-based frameworks alone is highly problematic. We conclude by urging a cautious, flexible approach that recognizes both the scientific promise of SCBEMs and the normative need to prevent the circumvention of regulatory safeguards.