There were three surviving members of the starship Franklin's crew when it crashed on the planet. All three were humans. (We see their images on the screen at the end of the movie as their files are each marked "case closed.") The captain became Krall; the other two crew members were Manas, Krall's henchman who killed Jaylah's father, and Kalara (I think?), who lured the Enterprise into Krall's trap and died when the ship's saucer section fell on her. All of the other soldiers and pilots (the guys in the black helmets that glowed green) were the "drone army" the captain mentioned in his ship's log. They made his force look more threatening, but when not in their ships, they didn't seem smart enough to do more than simple tasks they were programmed for. We know that the alien technology Krall found did two things-- it extended life, and it changed people's appearance. I think the two were directly related in a way the movie didn't explicitly state. We only ever see Krall using the alien technology's life-draining capability, but I think Manas and Kalara(?) had to be using it too, or else they would have died of old age. Why, then, do they all look like aliens at the beginning of the movie while Krall gradually returns to a human appearance? Because a side-effect of the technology's life-extending ability is that it causes the subject to take on some of the traits of the species they drain the life energy of. The three Franklin officers looked alien because they had been keeping themselves alive by stealing the life energy of whatever aliens came to the planet. This could include scavengers like to one's who threatened Scotty, Jaylah's people, and anyone else unfortunate to wander along. This also explains why the three officers varied in appearance-- in all likelihood they each had a different combination of alien traits based on who they had stolen life from. Once he has taken the Enterprise crew, Krall finally has access to humans for the first time in a century. You'll notice that he only drains life from human members of the crew. That's why he gradually regains his human appearance, which is part of his plan to infiltrate Starbase Yorktown. The only thing I'm not sure about is what language Kalara(?) was speaking during her ruse, since it had to be something the translator wasn't familiar with. Maybe it was based on writing discovered on that planet? What do you think? Does my interpretation make sense?
I think they're DNA got overwritten by the DNA of the people they sucked dry ... and that changed their appearances as well as their character traits. You know what ... I really miss all this techno/med babble from the TNG era.
I'm just grateful the movie didn't grind to a halt and spend 5-10 minutes explaining it. The OP theory is sound, fits what we see and implies the filmmakers believe the viewers are intelligent enough to reason something like this on their own. I LOVE it when filmmakers do that.
That was pretty much exactly my take. I think the movie wanted to imply that as well, and Uhura even hints at that when she says something to the effect of "When Krall drains energy it changes him." When they realized that, and when they saw he had drained one of their crewmembers on the Franklin, they realized he had changed his appearance again and looked slightly more human; their description of him to the security teams wouldn't be accurate anymore. Krall probably knew that too, which is why he drained that one officer (it's not like he NEEDED to, but he needed to change his face enough to pass for an alien crewmember and not look too unusual in a Starfleet uniform.
^ It's not that hard to rationalize. Kolrad guessed it right, so did I. Hell, even my dad managed to work that out on his own; he's the guy who originally didn't like Search for Spock because he thought the ending was too confusing
That's the one part that might warrant contradicting. The "there are just three of us still alive" bit actually comes pretty late in the game if we listen to Edison's rantings: the crash comes first, the failure to get rescued then follows, and then the crew gets reduced to just three. That these would be the three prominent humanoids on the evil side might well be nothing but coincidence. The planet is teeming with random people, any of whom could play out the role of the traitress. Only Krall ever displays any tendency to change shape, too. Timo Saloniemi
Actually, they did explain Khan (it just wasn't overly explicit). He says (paraphrasing): "John Harrison was a fiction invented by Marcus to conceal my true identity." Just as the OP reasoned out how the life-prolonging tech probably works, many people simply reasoned out "surgical alteration" as part of the invented fiction. (I, personally, didn't care about the change in look--same goes for all the cast--but once I came across that line of thought, any tiny qualms I had about Khan's appearance vanished altogether). YMMV.
FWIW, that's the explanation they went with in the IDW comics. And Khan was actually kind of pissed about it.