Malayan pangolin coronaviruses carry the same six key RBD residues and thus an equally human-ACE2-optimized RBD, showing this solution exists and arises in nature; the SARS-CoV-2 RBD therefore need not have been engineered and is consistent with natural acquisition.
Reasoning
A key objection to natural origin is that the human-ACE2-optimized RBD is too special to have arisen naturally. The presence of the identical six-residue configuration in pangolin coronaviruses - organisms and viruses with no laboratory involvement - directly refutes that objection: nature independently produced this binding solution. Given the solution is available in the wild, SARS-CoV-2 could have acquired it by recombination with, or descent from, such an animal virus, with no need for design. The authors state this clearly shows the SARS-CoV-2 spike optimized for binding human-like ACE2 is the result of natural selection.
Verdict — approved (checked)
Reconstruction. Premises: (i) Malayan pangolin coronaviruses, with no laboratory involvement, carry the same six key RBD contact residues as SARS-CoV-2; (ii) an objection to natural origin holds the optimized RBD is too special to arise naturally. Load-bearing step: an existence proof — the solution is instantiated in a demonstrably natural virus — refutes the “too special to be natural” premise, so a natural acquisition path (recombination with, or descent from, such a virus) is available and the RBD need not have been engineered.
Evaluation. Conditional on the premises the step is straightforward: a single natural instance defeats a universal “cannot arise naturally” claim, and yields the stated modal conclusion (need not / consistent with). The candidate undercutting defeater — that a lab could equally have started from a natural pangolin virus, so existence-in-nature is not evidence for natural origin — does bite a stronger conclusion (“therefore natural”), but the statement asserts only possibility/consistency, which the defeater leaves intact. (The body’s closing paraphrase of the authors’ stronger “result of natural selection” wording is reporting, not the argument’s own claim.) Approved; the existence-proof logic is elementary and traced author-blind.