Omicron did not come from delta. Yes, you read that right. Omicron came from the original strain itself, the wild type that was at the origin of the pandemic. I had long assumed that since delta was the dominant strain, and spreading in so many people, it would naturally be the one to evolve into the next variant. After all, mutations happen with a particular probability. The more hosts the virus replicates in, the higher the likelihood of the development of a mutation that helps it spread. Delta had plenty of hosts to experiment with producing different mutations, whereas the wild type did not have as many to try with. But shockingly, omicron came directly from the wild type, which we no longer even really hear about nowadays.
This trend isn’t new though. When alpha took over, it displaced the wild type everywhere it went. Surprise though, the delta variant came from the wild type, and not alpha, despite the wild type having been made obscure by the alpha variant.
This is a phylogenic tree, where the wild type is at the center, and the variants are portrayed as spokes coming out from it. If a variant has subvariants, as we can see delta has many, then the spoke divides into several sub-spokes. Note that none of alpha, beta, delta, gamma, or omicron is descended from each other! They are all independent variants that came from the wild type. This is particularly surprising with delta and omicron, since they evolved from the wild type even though it was far from the dominant variant.
Here’s my hypothesis on why. First, I’ll give a simple analogy, which may not be exact, but should drive the idea home. Let’s say we have a ball of clay, and we want to turn it into a sculpture to be sold for the greatest amount of money possible. We could make a clay vase sculpture, and we find out its value is $100. We decide to add a handle to it, which increases its price to $125, and etch a few designs into it, which increases its price further to $140. Despite our modifications, the vase is still a vase, and we have not done any serious transformations to it. Alternatively, we could have turned the clay ball into a clay sculpture of the Eiffel Tower. That goes for $300. We can add more details and refine it, making it sell for $350, but it’s still the Eiffel Tower. So from my ball of clay, I can make either a vase or an Eiffel Tower. My choice was final, I could improve the model I chose, adding its price, but I couldn’t change it entirely. So my question now becomes: would it be easier to make an Eiffel Tower from 1000 vases, or from a single ball of clay?
By now you probably see where this is going. The wild type represents clay ball which has the potential to mutate into an array of viruses, whereas the delta is already a sculpture that consists of a series of mutations. To get a virus that was dramatically more successful, just as the Eiffel tower fetches thrice the price of the vase, COVID started over from its own ball of clay, the wild type. We see that delta has its own tree with descendants of its own, but they’re very similar to delta itself, in the same way that we can slightly modify our clay sculptures after we decide what they’re going to be. This is regardless of how many hosts delta has to attempt to mutate, 1000 vases are never going to make a single Eiffel Tower.
This analogy isn’t complete, the evolutionary reality is a bit more complicated, and I hope to elucidate on it in another explanatory post. Until then, see you in the next one, get out of here!
