Here's a theory i haven't seen anyone post about lmk if i'm wrong might be a lot of speculation but here goes (my first post so i hope this is the correct place to put it)
I was watching a KOL video about the recent Onigashima island panel and how large the giant who's skull rests there must be, giving rise to the possibility that that giant is a literal continent puller. This had me thinking about the other large creatures seen in one piece, with one of the only other 'mammoth' creatures we have seen in Luffy's time being Zunesha. If Zunesha is a giant elephant who is roughly 1000 years old, where are the other elephants? There is no evidence of any other 'Zuneshas' existing present day. This must be because they have all died, presumably of old age. Considering the sentence that Zunesha was given to wander the earth, at what point is this sentence complete? Until Zunesha dies (it seems brutal in the scope of one piece if this is the case as eventually Zunesha would die and the home of the minks would be destroyed, possibly wiping out the race)? Or until a specific time? It also stands that we should question who or what gave Zunesha this sentence. Could it be that Zunesha was ordered by the other existing giant elephants? if so why does Zunesha continue to wander even though the rest of their species has long died off? it seems that Zunesha is physically bound to it's command (as shown by it asking Momonosuke's permission to slap jack). I think it is more likely that Zunesha was ordered by a person (following themes of humans like luffy having control over animals), which is supported by the fact that zunesha turns to Momo (a human) for permission.
Enough with all the questions. my theory for why Zunesha is the only living mega-elephant is this; the immortality operation of the ope-ope no mi was performed on it, giving Zunesha everlasting life (to the benefit of the Mink clan). This begs the question regarding the OP-ness of the ope-ope no mi. Is it possible that we do not know everything about the ope-ope no mi? Could it be that performing the immortality surgery at the expense of the users life comes with a caveat, that the now immortal being must follow the will or a rule of the fruit's user? This would make the ability less overpowered and follow the theme of 'devil fruits', that the condition is a curse, not a blessing (just like sacrificing the ability to swim). This is the reason why Zunesha physically CANNOT disobey their order.
Let's play about with this idea a little. This section of the theory follows from one linked below which i will outline (don't necessarily agree 100% but seems pretty good). It that says that Zunesha was used by JoyBoy to pull the Noah from Wano (where it was possibly built) to Fishman island, for the Fishmen to board it and aid in JoyBoy's battle against the world government. Only Momo has the ability to talk to Zunesha, because he is a descendant of joy boy's bloodline, with Toki (possibly being JoyBoy's daughter or sister) having travelled forward in time and being Momo's mother. JoyBoy punished Zunesha to walk forever because he screwed this plan up. this still does not explain why Zunesha is physically unable to disobey JoyBoy's will. At this point the speculation meter is quite high but could it be that JoyBoy had the power of the Ope-Ope No Mi and gave Zunesha immortality in order to carry a poneglyph and save one race from the wrath of the world gov?
We can also think about Im. it seems that Im is the ruler of the world and may have been living for a long time. is Im another recipient of the immortality surgery? (even if you do not believe the rest of the theory this is still plausible as it seems that Im has the influence of someone who is immortal, and otherwise why was the immortality surgery introduced in the story, as it seems unlikely that law will use it on luffy as i think luffy will die at the end of the show just like roger). If so, what is Im's command? To eliminate the pirates as they are a danger to the world? perhaps just to protect the world? I think that Im is not as villainous as we would make him out to be (he is pictured surrounded by flowers and butterflies when we meet him) even if the world gov eliminated the Ancient Kingdom, maybe this is because they perceived them as a threat to the world's peace. Regardless it could be possible that Im is under some sort of control and does not want to control the world like this but has to (which is why he doesn't speak). Maybe Joyboy for some reason gave immortality to Im and not zunesha (with Zunesha being controlled by some other method) i say this because there is a clear link with Im and Joyboy as Im has the straw hat which is likely Joyboy's (Oda just loves to fuck with us). At this point i'm just spitballing and playing with the ideas so I'll just end here.
oh wait here is a strange commonality between zunesha and Im which could be so fat foreshadowing, their eyes are the same!
(don't know if these pics will show up someone help me post the photos if not)
theory which helped me
Thank you for reading and please respond with your thoughts!