The evolution of language — descent traced by regular law

Languages descend like living lineages, and the descent is RECOVERABLE — the comparative method is one of the humanities' deterministic sciences. English 'father' descends from Proto-Indo-European *ph2ter, cousin to Latin pater, Sanskrit pitr, Greek pater; the path is traceable by rule. Sealed structure (https://narrowhighway.com/s/9c66f521565216319b7ab6cf3bca9314c18dfe3e9982b88459f714c61237c10f): a family tree is a phylogeny — 5 languages admit 105 possible rooted trees, 10 admit 34,459,425 (the double-factorial (2n-3)!!, the SAME formula biology uses for gene trees) — and core vocabulary decays EXPONENTIALLY, ~86% retained per millennium, a ~4,595-year half-life; the linear-decay misconception sealed BROKEN (https://narrowhighway.com/s/e456b15c210b9675bfdb7813c725256cd2c52b267665b9cc4518a826c6019545). Honest boundary, three colors: the sound-law REGULARITY is a strong empirical finding (Grimm, 1822); Proto-Indo-European itself is RECONSTRUCTED — every form marked with * to say inferred, not attested (a hypothesis, not a sealed fact); its DATE is genuinely CONTESTED (Steppe ~6,000 vs Anatolian ~9,000 years) — INCOMPLETE; and glottochronology's constant rate is HEURISTIC — a trend, not a law. Language evolves like life, and we read its fossils in the sounds.