The pulsar timing arrays detected the nanohertz background with Hellings-Downs correlations at strain 2.4 × 10⁻¹⁵ (NANOGrav 15-year), but standard supermassive binary populations built from observed merger rates and scaling relations predict about 1 × 10⁻¹⁵, short by a factor of a few even when every merger forms an efficiently hardening binary. Meeting the data needs masses, rates, and final-parsec efficiency all pushed to their edges at once.
The model's source inventory is fixed by its assembly history: binaries form from hierarchical mergers of galaxies whose black holes obey local scaling relations, capping the background's amplitude. A louder hum than the inventory allows forces either edge-tuned demographics or new physics imported wholesale.
SCT rewrites the source demographics that set the amplitude. Black holes are collision-seeded at 10⁷ to 10⁹ solar masses (P46) and overmassive relative to local scaling relations through cosmic history, the same demographic JWST observes directly, so the chirp-mass budget of the binary population is systematically larger than ΛCDM bookkeeping permits. Sibling seeds condensing from one debris field begin correlated and close (P31, P37), enriching the binary formation channel beyond what galaxy-merger counting captures: more binaries, heavier binaries, earlier binaries, and a louder integrated hum follows from the seeding inventory without pushing any parameter to its edge.
The final-parsec bottleneck also eases: binaries embedded in dense seeded environments harden against the natal gas and debris (P25), and mesh dissipation (P14) adds a slow secular drain on wide orbits, so the population spends its history radiating rather than stalling. The spectrum carries the test: a seeded population whose binaries harden against gas and mesh drain spends less time in the lowest-frequency octaves, flattening the strain spectrum relative to the canonical -2/3 slope and shifting spectral weight toward higher frequencies: the direction of the observed departure (NANOGrav's residual index near 3.2 against the canonical 13/3).
This is the same seeds-before-hosts demographic behind the JWST overmassive ratios and the quasar clustering excess, now audited in gravitational waves. There is no need to invoke cosmic strings or edge-tuned conventional demographics.
This resolution is developed in Paper 1, From Chaos to Convergent Foundations.
The attribution race is the test: SCT requires the background resolved into a binary population that is overmassive and early relative to local scaling relations. Individual-source detections and anisotropy mapping revealing a binary population fully consistent with local relations and standard merger rates, with the amplitude excess dissolving into improved noise modeling, would remove the seeded-demographic signature; equally, a confirmed primordial origin (strings, phase transition) displacing binaries entirely would falsify this reading while raising its own conflict with SCT's no-inflation tensor floor.