Courts routinely cite obiter dicta from prior decisions as if they were ratio decidendi, constructing genealogies of apparent doctrinal continuity that mask substantial normative innovation. The phenomenon is well documented in Anglo-American, Australian, and Canadian jurisprudence, yet the existing literature describes what happens without explaining why it works, why it persists, or why it accumulates. This paper proposes a causal mechanism grounded in three interconnected frameworks from evolutionary biology and cognitive science: Extended Phenotype Theory (EPT), which models obiter dicta as latent memes activated through the reproductive machinery of stare decisis; Heteronomous Bayesian Updating (HBU), which explains why legal operators follow promoted obiter without verifying its doctrinal status; and Evolutionary Game Theory (EGT), which demonstrates that obiter promotion is a dominant strategy yielding the benefits of doctrinal innovation at a fraction of the reputational cost of explicit overruling. I apply this framework to the Argentine Supreme Court's emergency doctrine chain, tracing five landmark decisions from Ercolano (1922) through Bustos (2004). The genealogical reconstruction identifies three distinct types of doctrinal migration operating simultaneously: status migration (obiter to ratio), institutional migration (legislature to executive), and functional migration (regulation to deregulation). The case study reveals that each link in the chain drew its authority from the broadest propositions of prior cases rather than from their narrow holdings, producing a cumulative doctrine of presidential emergency power that no single decision's ratio ever established. Comparative analysis with Colombia (where the ratio/obiter distinction has been formalized) and Australia (where the category of "seriously considered dicta" was introduced) suggests that formal doctrinal constraints are insufficient to prevent obiter creep when the underlying cognitive mechanism (HBU) remains operative. The paper generates five falsifiable predictions, including that jurisdictions with higher Constitutional Lock-in Index scores should exhibit greater rates of obiter promotion. This represents the first application of evolutionary theory to the specific phenomenon of obiter-to-ratio migration.
Ignacio Adrián LERER (Tue,) studied this question.