Why Scientists Think The Novel Coronavirus Developed Naturally — Not In A Chinese Lab

But, Garry said, the tip of the SARS-CoV-2 spike is unlike anything scientists have seen before, sharing only a single key amino acid with SARS. Modeling suggests that it shouldn’t be able to bind to human lungs well, but the new configuration is about as effective as the optimized SARS.

How SARS-CoV-2 acquired this unusual tip is still a mystery. But blaming it on genetic engineering overstates the abilities of scientists, Garry said. Guessing that these particular amino acids can bind to ACE2 so effectively is nearly impossible— there are 20 common types of amino acids, and tens of millions of ways to arrange them into a binding tip. It would be like if you looked out over the proverbial infinite monkeys with their infinite typewriters, guessed that a specific macaque would type out King Lear, and then picked the right animal.

The virus’s spike has a hinge-like structure, allowing the spike to change shape as the virus enters the host cell. Like the spike tip, the hinge on SARS-CoV-2 is markedly different from anything seen in its close relatives. New research suggests that the hinge loses its unique characteristics when cultured in a lab, said Garry. The spike also appears to be able to shield itself from antibodies—another hint that it evolved in the presence of host immune systems.

Most importantly, there’s no smoking gun connecting the lab to an ancestor of the virus. There’s “no bat virus that’s close enough to be the progenitor,” said Garry. The closest known relative to SARS-CoV-2 is a cousin that diverged decades ago in bats.

And while critics suggest that the WIV might have concealed the ancestral virus, 27 scientists who have collaborated with the WIV, including former U.S. officials, rejected the idea in a letter to The Lancet.

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