Jadzia Dax’s death in episode 6.26 of Deep Space 9 (“Tears of the Prophets”) is one of the few scenes from the series I have clear memories of watching as a kid. It was shocking, and crushing, on the first view—this is Star Trek, after all, not a show generally inclined toward killing off its main characters, and Jadzia was far from a red-shirt. I could never warm up to Ezri Dax my first time with the series. Like Worf on the show, I looked at her and could only see how much she wasn’t Jadzia.
I suppose I should back up a second for non-Trekkies. Jadzia Dax is a species known as a Trill. On the outside, they essentially look like humans with spots running down from their temples. What makes Trills truly unique is the symbiont, a worm-like being to which the humanoid Trill bodies can serve host. Symbionts are exceptionally long lived (the Dax symbiont is around 300) and retain the memories of all the hosts they join with—memories that are accessible by the current host. To be joined with a symbiont is a great honor in Trill society; applicants undergo rigorous testing and preparation to make sure they’re up for the task.
Ezri’s case is special, though. She never studied to be joined; she just happened to be the closest Trill when the Dax symbiont found itself in need of a host. In the early episodes of season 7, we see her struggling to adapt to the seven lifetimes of new memories inside her head, while the people who knew Jadzia are trying to figure out how to interact with this person who has her memories but isn’t her.
Watching these episodes now, I can’t help but think of Doctor Who and his regenerations. With each regeneration, the Doctor has to re-learn himself. It’s not only his face that changes but his tastes, his temperament, the way he thinks about the world. He has the memories of the old Doctor, but he’s a new man.
Jadzia was the seventh Dax host. The one immediately before was a man named Curzon, who had been a mentor and close friend of Captain Sisko before the start of DS9. Sisko calls Jadzia “old man” throughout, the name he used to call Curzon Dax. Having seen this transition happen before, Sisko is the least phased by the transition from Jadzia to Ezri—in a sense analogous to River Song, who’s seen the Doctor at enough points along his timeline to adapt to his many selves better than his companions, who have come to love and trust a man who is, for all practical purposes, dead.
Though it happened off-screen, I would imagine the transition from Curzon to Jadzia could be likened to the Doctor’s twelfth regeneration (from David Tennant to Matt Smith) in terms of its narrative impact—a relatively clean break with the characters from his past. There are a few like River Song who interact with both the Tenth and Eleventh Doctors, but for the most part no one is comparing him to the man he was before.
The transition from Jadzia to Ezri feels to me more like the thirteenth regeneration (from Matt Smith to Peter Capaldi). The Doctor goes from a lovably awkward nerd to an older, cynical, abrasive man—he keeps much of the awkward, but loses the charm. Worse, the new Doctor finds himself judged through the eyes of Clara, who has trouble accepting him as the same man she knew.
Good characters always change, if we spend long enough following them. With Trills and Time Lords, the transformations are more drastic, and the really interesting thing about these species is that they inherently raise the question of what makes you a self. They may share memories, but Ezri Dax is a completely new character from Jadzia. Sharing little besides memories, can you call the regenerations of the Doctor the same character? If your manner changed, your preferences, your face—would you still be you? I’m going to try to give Ezri more of a shot this time around, in any case. She may not be Jadzia, but as Quark tells Doctor Bashir: she’s the next best thing.