So do I understand correctly that a certain hox gene is activated in basically all cells which are in the “domain” of a certain vertebrae and they all activate some subset of homeobox genes which in combination with the original hox gene cause them to start turning into all the different parts associated with that vertebrae (so organs and other structures)?

Would we then need an entirely new hox gene to produce even a single gill? (I know you basically just laid out most of a response to this question.) Because I would assume although the exact point at which the development of our arms and legs begins is part of the whole hox gene “superstructure”, but couldn’t we ‘basically just’ highjack this same system and duplicate this gene to produce at least a single gill in the region where the current hox gene for our neck is expressed?

Long story short: what is the biggest reason why we can’t just hack into a later part of the sequence and continue on from there with what you said?

Or would your proposed plan also just end up like this in the final product and you laid it out like this because it’s already the most viable route into this mess? 😅

And that’s the thing:

Assuming it did, you couldn’t see it approach until it hit you because it’s moving at the speed of light! It could also have happened, but just super far away such that it will never reach us due to expansion between its origin point and us being faster than c!

Also just because the universe is frickin old doesn’t mean it is statistically bound to have happened. There are plenty of ways of making it even more astronomically unlikely but still possible…