u/Illustrious_Aerie502

I recently binged the entire show as a sci-fi lover and I started to have a few theories I wanted to see what people think about. I have tried to look these up and I cannot be sure how many of these are retreading old grounds.

First, before going into the virus origin, there are 4 bases, but there is no reason to presume that alien life would always have 4 base pairs, not more or less. We at least know of 2 synthetic base pairs that are possible and there is documentation that suggests we can have normal genetic replication with as high as 8 bases. Some people who study the matter do believe that AGCT are uniquely plentiful and that 4 creates a stable amount for what it is intended to accomplish, but it is also possible that this is just how it looks to people who have only seen AGCT DNA coding and a world where those chemicals are used by all life on the planet. Either way, there are other mechanistic ways that earth DNA is encoded/decoded that would not necessarily line up with this anyway, not to mention the specific cell biology of earth viruses that it was put into.

This could indicate a panspermia origin of life, a convergent evolution of the life on the planet of origin using the same bases, artistic licence (explaining a more accurate model was too hard or would confuse people), or the message was intended for humans and the alien species knew about earth DNA. I believe that the later two are the only major probabilities if this issue was considered by the author.

Now the big topic, why does the virus exist.

It seems very odd, it is hard to imagine a planet evolving with a virus that leads it's host to death which as far as we can tell is happening since the humans are all going to starve at least until reaching a population that is sustainable based on the methods of their supposed governing beliefs focusing on the sole ambition of transmitting it's genetic information to a new host planet.

It Is not impossible that the originating planet or organism did not have this problem because they are consuming something else like rock minerals or are plants, but I consider it unlikely.

The behavior sounds an awful lot like Cordyceps fungus that has an ant climb to the highest spot to spread it's spores when it consumes the ant it has infected.

The signal may also just be a weapon to destroy any competing lifeforms. A good example of why someone might make this is the events covered in the 3 body problem. To keep spoilers to a minimum suffice it to say that dangerous lifeforms near you are a potential threat, so some may see this sort of weapon as a defense against alien life that could try to destroy them.

All of these theories have major problems when you look at them through the lens of the first problem I brought up. But if we ignore that one, there are still a lot of problems, a more sophisticated alien may have done more work to discern the nature of the code and determined it's purpose or had more strict protocols for security and isolation to prevent it from leaving containment. It had to get so lucky with humans and also it will get so little out of them as it seems like they won't be able to send a signal for a substantial amount of time.

The aliens could have FTL travel but why send the signal from such a remote place instead of setting up a much smaller transmitter in a nearby solar system? What about humans 600 years ago was remotely threatening to them that they would try to destroy them?

Given all the points I have mentioned, I believe that the only solution that makes sense based on these theories and facts is that the origin of the signal is the progenitor species of this virus, they have an identical 4 base DNA with similar cell structure because of panspermia or some other event and are broadcasting the signal at earth because they broadcast it continuously at any apparently habitable exo-planet for some interval of time and are cycling through them. They are either doing this to pacify all their neighbors or to legitimately spread the virus. I am not convinced either plan will work but it could be their reasoning.

I don't think it is likely that we will see the progenitor species at all and if not at least for the first 3 seasons. It's a classic lovcraftian style to have an otherworldly enemy bring horrors beyond comprehension operating largely outside of our sight. Very similar to the 3-body problem series.