Can Polarized Cosmic Rays Select Biological Handedness? A Time-Integrated Bound on the Globus–Blandford Mechanism

Globus & Blandford (2020) proposed that biological homochirality is a deterministic consequence of the weak interaction: spin-polarized cosmic-ray muons, whose helicity has a universal sign, damage helical biopolymers of one handedness slightly more often than the other, and a per-event bias of order 10-7 in the mutation rate would, over enough generations, drive one chirality to extinction. Their Appendix C shows that a growth-rate difference δ between the two populations produces an enantiomeric excess ee = tanh(δT/2) after T generations. That result treats every muon traversal as a mutation and every mutation as a fitness loss. Here the missing links are put back: the bias acts only on the muon-induced share of the mutation rate; the mutation-rate difference maps to a selection coefficient through the Haldane–Muller mutation-load relation; and the outcome is compared with genetic drift. The resulting law, ee = tanh(Σ/2) with Σ = fdel δ Pμ Aq (U/Gy) Dcum, has a useful property: the generation time cancels, and the outcome depends only on the cumulative polarized-muon dose. With realistic inputs Σ ≈ 6×10-8 over 100 Myr and 3×10-6 over the age of the Earth; with every input at its most favourable bound, 6×10-5 and 2×10-3. Nearby supernovae add ~100 Gy per event to a baseline of 2×104 Gy per 100 Myr and do not change this. Reaching ee > 0.9 within 100 Myr would require a per-event bias of at least 7×10-3, some 20 times larger than the largest chirality asymmetry ever measured for spin-polarized electrons and 5 orders of magnitude above the proposed value; using the authors' own mass scaling for muons rather than keV electrons, the per-ionization bias at ground level is at most ~10-13, widening the gap to more than ten orders of magnitude. A Frank-type amplification stage does not rescue the mechanism: for the bias to beat demographic noise, a well-mixed population of 1018–1020 replicators would have to coexist racemically for 100 Myr or more. The calculation defines what a laboratory test would have to find — a per-event asymmetry of order 10-2 in polarized-lepton damage of a helical polymer — for cosmic rays to remain a viable origin of biological handedness. The accompanying archive contains the paper (PDF and DOCX), the Python script that reproduces all tables and the figure, and a README.