The argument is the direct animal-shedding prediction. In a scenario where a live animal at a stall is productively infected and shedding SARS-CoV-2, the environmental RNA it deposits should be spatially and quantitatively tied to that animal’s own biological traces (its mtDNA): samples richer in raccoon-dog material should tend to be richer in virus. Bloom’s quantification shows the opposite — the virus is most abundant in samples dominated by fish (largemouth bass, catfish, carp, snakehead) and livestock (cow), and is if anything negatively associated with raccoon dog and hoary bamboo rat, with 13 of the 14 raccoon-dog-dominated samples carrying no viral reads at all. Fish and cattle are not plausible SARS-CoV-2 hosts, so their strong association indicates the viral RNA is not indexing an infected animal but rather tracks surfaces, products, and drainage where infected humans deposited virus during a market that was, by the sampling date, already a human-transmission hotspot. On this reading the metagenomic co-location fails to single out raccoon dogs (or any susceptible mammal) as the shedding host. (Crits-Christoph counter that this whole-dataset correlation is confounded by the sampling design and by animal-before-human shedding plus RNA decay — a validity dispute step 6 must weigh.)
Verdict (step 6) — approved, checked
Reconstruction. Premise (the observed correlations): viral RNA abundance is highest in fish/livestock/human-dominated samples and null-to-negative with raccoon-dog and bamboo-rat mtDNA (13/14 raccoon-dog-dominated samples had zero reads). Shedding prediction: a productively infected live animal deposits RNA co-located with its own mtDNA, so a shedding host would produce a positive viral–mtDNA association. Load-bearing step: the observed absence of that positive association for raccoon dog → the metagenomic co-location does not support (undercuts) the raccoon-dog-as-shedding-host claim.
Evaluation, conditional on premises. The relevant undercutting defeater is the Crits-Christoph confound: with sampling weeks-to-months after shedding, plus decay and stall turnover, even a genuine shedding animal could fail to show a positive correlation, so absence of correlation is a weak instrument. Critically, this defeater cuts against a stronger claim — that the null proves raccoon dogs were uninfected (A-55’s territory) — but it does not rescue positive support for raccoon dogs from a null result: a null/confounded result simply fails to provide affirmative support. The statement’s operative verb is “undercutting the specific raccoon-dog-shedding claim” (i.e. removing support), and “expected if… human deposition” is consistency language, not proof. That epistemically-safe residual survives the defeater. Approved (the inference does not license the stronger affirmative “human deposition is proven,” but the statement does not assert that). Traced directly — checked.