We Now Know How Old Man Cap Got Back To The Main Timeline
Directors Joe and Anthony Russo combined arguably the most confusing element of Avengers: Endgame with one of the most heart-wrenching moments in the last few minutes of the film, which saw Chris Evans' Steve Rogers returning from his final time travel mission as an old man, gifting his shield to Anthony Mackie's Sam Wilson, and keeping coy about his wedding band (that we all know was a sign he got married to Hayley Atwell's Peggy Carter). Once the fuzzy feelings that the scene inspired faded, though, fans were left scratching their heads and wondering how exactly Old Man Cap got back to the main timeline, as his appearance seemingly contradicts the rules of time travel as previously outlined in the movie.
Finally, more than three months after viewers first watched Avengers: Endgame up on the big screen, we have the answer.
The Russo Brothers recently held an AMA (Ask Me Anything) session on Reddit, where they detailed how the grizzled Captain America found his way back to the main timeline without completely shattering the established time travel theory the Ancient One (Tilda Swinton) stated early on in Endgame.
A fan asked the Russos how Cap came back to the present after returning the Infinity Stones to their respective places in the past, and requested some clarification on the rules of time travel. According to the Ancient One, when someone takes a Stone from its original place and travels through time, they create a branched timeline that doesn't alter the past. When Steve Rogers returned the Stones following the big battle against Thanos (Josh Brolin), he wore a quantum suit and used a Pym Particle to travel back in time. But when the older Steve appeared on the park bench at the end of Endgame, he wasn't in a quantum suit. Did Cap figure out a way to come back to the present without using the same method that sent him to the past? Did he live out his life with Peggy in the main timeline, thus creating two separate Captain Americas and countering the rules of time travel, or did he marry her in an alternate timeline and keep everything in tact?
The pressing question from the fan was one many have asked themselves before: "If Captain America was in a different time line when he returned the stones, how did he back to the main time line without the use of the quantum suits?"
The Russos confirmed that Cap "would have had to have worn the quantum suit" and used a Pym Particle to re-join the present timeline, just as he needed to do to jump back to the past. But the reason why he isn't sporting the silvery suit on the bench is because "that is not the exact moment to which he returned."
So, there you have it: Cap did indeed return to the main timeline using the quantum suit and a Pym Particle, but he was hanging around in the year 2023 as a wrinkly, white-haired old man at least long enough to change out of the suit and into something your bird-watching grandfather would wear.
This explanation indicates that Joe and Anthony Russo are of the opinion that Steve and Peggy reunited, got married, and shared a full and happy life filled with many evenings spent dancing in their living room all in a timeline alternate to the main one of the Marvel Cinematic Universe. Joe Russo even told Entertainment Weekly in May 2019, "If Cap were to go back into the past and live there, he would create a branched reality."
However, not everyone involved with Avengers: Endgame agrees with that assessment. Screenwriters Christopher Markus and Stephen McFeely have maintained their belief that Steve's grand plan to finally spend his life with Peggy happened in the main timeline — meaning that there are two Captain Americas in the MCU.
Just after the release of Endgame, Markus and McFeely sat down with Fandango's Erik Davis, who asked if Cap's ending means that "an old Captain America was hanging out this whole time while another Captain America was saving the day?" Markus confirmed that that is his and McFeely's theory, and that he personally rejects the idea that Steve was ever in an alternate timeline.
"We are not experts on time travel, but the Ancient One specifically states that when you take an Infinity Stone out of a timeline it creates a new timeline. So Steve going back and just being there would not create a new timeline. So I reject the 'Steve is in an alternate reality' theory," said Markus. "I do believe that there is simply a period in world history from about '48 to now where there are two Steve Rogers. And anyway, for a large chunk of that one of them is frozen in ice. So it's not like they'd be running into each other."
It's hard to say whether the two directors or the two writers are more accurate here, since time travel isn't actually possible (yet), but the Russos' explanation better aligns with the rules of time travel established in Avengers: Endgame. Even so, Markus and McFeely have said that Cap's ending is open for interpretation. Though he and McFeely prefer their theory to the Russos', Markus has said that the issue of whether Steve's life with Peggy happened in an alternate reality or in the main MCU timeline is "a question with many answers."
So, mystery sort of solved? We'll leave it at that.