Abstract
<title>Abstract</title> <p>The Life-Ratios Hypothesis (LRH) is a parameter-free framework for DNA-based habitability in polar-hydride solvents. The central claim is that DNA function is constrained by dimensionless ratios of molecular energies to the thermal scale (kBT), not by absolute energies. The framework is calibrated on terrestrial life in liquid H₂O via the solvent-network hydrogen-bond dissociation ratio (Rdiss(l) = DHB(l)/(kBT)) over the observed temperature range of reproducing life. Three falsifiable results follow. First, a bond-replacement self-cancellation theorem: when a Watson-Crick base pair opens in a polar-hydride solvent, the enthalpic hydrogen-bond residual cancels topologically whenever a solvent non-hydrogen atom matches a base nitrogen or oxygen. The cancellation is near-exact in water—matching the calorimetric A·T/G·C enthalpy equivalence of Privalov and Crane-Robinson—and exact in ammonia. Second, the postulated cross-solvent invariance of Rdiss(l) yields a parameter-free +7.25 K biological-temperature shift for D₂O, matching the observed +7.2 K shift in the temperature of maximum density. Third, the same transfer applied to NH₃ predicts a cold solvent-network window of 198–270 K, with optimum 226 K, accessible at 0.07–3.73 atm, and explicitly excludes warm or hot ammonia-based DNA biospheres as a negative prediction. Combined, the results give a continuous habitability corridor across H₂O–NH₃ mixtures, from 226 K in pure ammonia to 310 K in pure water, over wide pressure ranges. The corridor defines where DNA-based or DNA-like life should be sought if such biochemistry is possible; it does not imply that such life exists.</p>