I'm trying to find an old story that I think had been on FurAffinity for a while... and thus this is all from memory....

But it was a macro story that dealt with humanity returning to Earth after an apparent absence of some sort to find various animal species have turned to giants (or maybe they shrank? Again from memory), and dealt with two dominant kingdoms... Cats and Dogs reacting to two separate collections of humans.

Any of this ringing any bells?