reasoning
There are no obvious natural sources for SARS-CoV-2 in the Wuhan area (Hubei); the most similar coronaviruses are in bats that don’t live nearby, and no precise natural spillover point has been identified. On its own that cuts against zoonosis. But the observed initial cluster of cases at the Wuhan wet market is significantly more likely if the virus originated zoonotically. Rootclaim’s net treatment of this factor leaves zoonotic unchanged while dividing lab-escape, bioweapon, and zoonotic-collection each by 2 — i.e. the factor favors natural spillover. Running likelihoods: Zoonotic 68%, Lab-escape 6%, Bioweapon 0.9%, Zoonotic-collection 25%. This is the main factor Rootclaim credits to the zoonosis side.
Step 6 assessment
Reconstruction. Premises: (a) no obvious natural reservoir for SARS-CoV-2 near Wuhan (cuts against zoonosis); (b) an initial case cluster was observed at a wet market selling live wild mammals. Load-bearing step: a first-case cluster at a live-wild-mammal market is more expected under wildlife-trade zoonosis than under a lab leak (which would predict a lab-worker-centred cluster), so netted against (a) the factor still points to zoonosis.
Evaluation. The directional step — market cluster is more likely under zoonosis than lab — is valid likelihood reasoning. The live undercutting defeater is ascertainment bias (early cases were found at the market because that is where surveillance/attention focused), which if total would drive the market signal toward uninformative. But that defeater competes on the strength/reality of the cluster signal and is carried by its own dedicated nodes (A-18, A-40, A-44) that price the observation at step 8; it does not negate the inferential step conditional on the premises, and the claim here is already the modest evidential form (“favors,” net ÷2), not “proves.” No defeater breaks the step given the premises. Approved; step traced directly, checked.