The basis for my theory:
If we developed warp drive, genetic manipulation, and transporter tech, I’d reckon even before that we’d first figure out how to make dogs live for hundreds of years. Because that’s easier and of course we would.
I’ve seen people post that it must have been like Porthos v9 because of the time difference, but there’s no way that dog didn’t outlive Archer by decades, because if we’re going to do anything good as a species, it will be making sure our dogs outlive us.
So Scotty lost the OG Porthos.
e: better phrasing
In which episode did Scotty lose a beagle?
Scotty in the 2009 Star Trek movie explaining how he wound up in an especially remote posting.
In the reboot movie.