Evolutionary Singularity and the Last Universal Common Descendant: Evolution as a Self-Terminating Boom-Bust Process

Evolution is conventionally framed as an open-ended process producing indefinite diversity and complexity. This paper proposes that evolution driven by optimization pressure is self-terminating: the same selective forces that produce diversity progressively eliminate the conditions - variation and competitive selection pressure - that make evolution possible. The terminal state is reproductive singularity: clonal stasis in which life persists but evolutionary change ceases. The paper identifies the specific biological mechanism of this termination - the sequential abandonment of sexual reproduction as variation loses competitive value - and proposes observable biosignatures for both the boom phase and the stagnation phase of the evolutionary arc. It further proposes that the Last Universal Common Ancestor (LUCA) is more precisely described as the Last Universal Common Descendant (LUCD) of a prior cycle: not an origin point but a cycle junction, the surviving dominant form of a previous boom-bust arc whose stasis was broken by external disruption. A framework for astrobiological application is developed, including: apex predator loss as a measurable pre-stagnation signal, introduced life on a stagnant planet as a testable experimental prediction, and the managed reset hypothesis - that sufficiently advanced non-Earth intelligence could identify and deliberately disrupt planetary evolutionary stagnation. These hypotheses are conceptual; quantitative modeling and observational testing are invited.