Kimura’s (1968) derivation of the neutral substitution rate k = μ rests on the cancellation of population size N between mutation supply (2Nμ) and fixation probability (1/2N). This cancellation is invalid. The mutation supply term uses census N (every individual can mutate), while the fixation probability is governed by effective population size Ne (drift operates on Ne, not N). The corrected substitution rate is k = μ × (N/Ne). Using empirically derived Ne values—human Ne = 3,300 from ancient DNA drift variance (Day & Athos 2026a) and chimpanzee Ne = 33,000 from geographic drift variance across subspecies (this paper)—we recalibrate the human-chimpanzee divergence date. The consensus molecular clock estimate of 6–7 Mya collapses to 200–580 kya, with the most plausible demographic parameters yielding 200–360 kya. Both Ne estimates are independent of k = μ and independent of the molecular clock. The recalibrated divergence date increases the MITTENS fixation shortfall from ~130,000× to 4–8 million×, rendering the standard model of human-chimpanzee divergence via natural selection mathematically impossible by an additional two orders of magnitude.