Evolution, as always, is more inventive than us.
A common conspiracy these days is that COVID has been cooked up in a Chinese lab in order to bring the West to its knees. Aside from the issue that China was also very badly affected and bore the early brunt of the pandemic, the genome of the virus can be used to scan for evidence to support or refute this story. A lab has done it, I read the paper, and here’s my interpretation.
The 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”, which is the offensive appendage bit that invades our cells:
1. One part (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—but wait, this new one’s using an iPhone, which seems to be as good as the other phones, 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 for the engineers to use a known and simulated “optimal” binding protein (the Android phone) rather than invent a new-to-science and unpredictable solution.
2. COVID-19 has a distinct feature called a “polybasic cleavage site” (PBS from here-on). It’s distinct because 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 thing does, and it’s not in all the other Coronaviruses, 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.
Genetically, the closest virus 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 in the world. There are shitloads out there making animals sick every day and we just don’t get to 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 a civet, 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.