I don't know what's going on with that. Did Trump suggest it came from a lab maybe? If so, it would obviously be obligatory to believe otherwise.
It's correspondence, so not peer-reviewed.
There are two parts to their argument, the first part:
So if it functions differently than they predicted, that doesn't mean that it doesn't function as someone else had predicted or arrived at through trial and error.
The second part:
Except that
this lab was able to synthesize SARS-CoV-2 from scratch - a methodology that leaves no evidence, or maybe the Chinese researchers simply used a backbone not previously used, or maybe they just artificially selected it in the lab, which would undermine both of the authors' arguments. It would be like arguing that golden retrievers evolved naturally because there is no direct evidence that their DNA has been tampered with.
They do note the insertion of the furin cleavage site, but say it's function is unknown. That's odd, because I know, but moreover, here are
one, two,
three, and
four studies in which furin cleavage sites were inserted into SARS-CoV in order to study how much it increased its infectivity. And then we have this
Chinese study from 2019, which I’ll quote:
It's remarkable that the authors didn't know any of this. I'll quote Dr Ronen Shemesh again:
The authors believe the insertion, that is the insertion of code for four amino acids, evolved naturally. Though extremely unlikely in the time frame in my opinion, this is theoretically possible if it serves an evolutionary function, but none of the closely related coronaviruses that infect bats have it. It makes the virus extremely infectious in humans, but apparently doesn't help in bats, so how then would such a complicated change be naturally selected for in bats?