Evolution, as always, is more inventive than us.
This paper finds compelling evidence for this virus having arisen via evolution, and therefore, evidence against it being an engineered virus.
It finds that COVID-19 has two unique features in it’s “spike protein” (the offensive appendage bit that invades our cells)
1. One bit (the receptor binding domain or RBD) is unusually efficient at binding to our cells. But not in an optimal way you would predict from the ways all other known Corona viruses use. It’s a bit like all the other Coronaviruses you know using Samsungs, and Google Pixels, and Sonys, which are all awesome—but wait, this one’s using an iPhone, which seems to be as good but in a distinct way.
So it’s a different, but very efficient way to bind to our cells. If this were lab made, it would be easier to use a known and simulated “optimal” binding protein (the Android phone).
2. COVID-19 has a distinct feature called a “polybasic cleavage site” (PBS from here-on). It’s distinct cos its not in any of the other Coronaviruses in COVID-19’s lineage. The function of this is unknown, but there’s scanty evidence from other studies that features like this in other viruses can increase transmissability within and between hosts. We don’t know how/why.
The presence of this feature is evidence against COVID-19 being engineered, because if science simply doesn’t know what this thingy does, and it’s not in all the other ones, why would anyone cook one up with it in?
So where did COVID-19 come from?
We know the first cases were centered around one of those bloody awful “wet-markets” full of wild animals destined to be ground into Chinese placebos.
The closest virus genetically to COVID-19 is from a bat. But despite 96% genetic similarity, the related bat Coronaviruses don’t have the RBD-similarity and PBS features.
Also very close to COVID-19 are Coronavirus observed in Malayan Pangolins (one of the most dear little mammals you will ever set eyes on). While not quite as close as the bat ones, the pangolin viruses DO have a similar RBD bit.
The PBS thing is still lacking in both bat and pangolin viruses we know. And here it is worth pointing out that we don’t know *most* viruses. There are shitloads out there making animals sick every day and we just don’t observe them.
So, two strong theories for the origin:
A) The virus coincidentally adapted to us while rocking around in an animal host, then jumped to humans. We know that human-adapted RBD features can evolve in nature (thanks pangolin!), so COVID-19 could have come from a reservoir of wild animals with a similar enough binding domain to humans to select for this RBD adaptation. This could have been a cat, or a ferret, or who knows. Then through mutation, the PBS thingy arises and it jumps to humans and goes nuts.
B) The virus could have evolved just the RBD adaptation in its animal hosts, then jumped to humans. It could have remained at low levels of transmission and virulence for a while, lurking around making Chinese people mildly ill, until it struck the lucky mutation to result in the PBS feature then goes nuts.
I am not a virologist, or a molecular biologist. So if this is a bit dumbed down and imprecise, sorry.