We don't know the exact details, but at the end of Avengers: Endgame we see Captain America

going back to return all the Infinity Stones to their time lines. After that, he chooses a specific point in time in which he can have a "normal" life with Peggy, thus, creating another branch in the flow of time. We know from other questions/answers that he found some other way to go back to the main time line, and have that conversation with Falcon.

However, when he

returns to the main time line, he is old!

Why did that happen? Does he follow a regular process of aging as any other human being? Or did he find a way to extract the super serum injected to him in the 1940s?

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    Because he went back in the 70s and lived another 50 years until the present time in movie?
    – Hans Olo
    Commented May 9, 2019 at 15:22
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    @Rebel-Scum but wouldn't the super serum stop aging on him as it did while he was "sleeping" in the ice for aprox. 70 years? Commented May 9, 2019 at 15:25
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    @KennyBarrera Pretty sure the ice kept him from aging for those 70 years, not the serum.
    – svenvo7
    Commented May 9, 2019 at 15:37
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    @Rebel-Scum: “Because he went back in the 70s and lived another 50 years” — judging by the car that drives by the house he's in, I suspect he went back to the 1940s or 50s and lived another 70-80 years. Although as he's apparently travelled back to his original reality, he might have travelled in time too, so maybe he lived 200 years. But I don't think we've ever been told that post-serum Steve ages differently in the MCU. Commented May 9, 2019 at 15:41
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    @PaulD.Waite Christopher Markus dates Steve going back to 1948, see my answer.
    – TheLethalCarrot
    Commented May 9, 2019 at 15:42

2 Answers 2


Because the serum only slows down the ageing process

Steve was born in 1918 as mentioned by Zola in the below quote, I believe his birthdate is 4th of July and I think that is mentioned in Captain America: The First Avenger but I can't find reference to that now.

Dr. Arnim Zola: Rogers, Steven. Born, 1918.

Captain America: The Winter Soldier

He then goes into the ice in 1945 and is brought back in 2011 in Captain America: The Winter Soldier when SHIELD finds him. This would put him at 93 physically but the ice stopped the ageing process so he is technically only 27.

Fast forward to the end of Avengers: Endgame and we are in the year 2023 where Steve would be 105 years old physically or 39. He then decides to go back in time and according to Christopher Markus he travels back to 1948.

Fandango: So people are asking... Does this mean an old Captain America was hanging out this whole time while another Captain America was saving the day?

Christopher Markus: That is our theory. 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.

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.


Seeing as Markus also states Cap lived in the main timeline the whole time that would mean at the end of Endgame he would be 180 physically or 114. For a 114 year old he looks to be in remarkable shape, probably of someone in their 80's and so I think we can assume he just ages slower than the rest of us.

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    “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.” For goodness sake Markus. You wrote the damn thing! This is your job! Commented May 9, 2019 at 15:43
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    So does this mean that during the brief time in 2011 when Cap Prime goes back to steal Loki's staff, there are three Steve Rogers in that time?
    – TylerH
    Commented May 9, 2019 at 16:37
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    And also, Cap Prime suffered twice from the effects of the snap.(Although the second time he knew everything would end "fine", he saw the people suffering twice.)
    – Moacir
    Commented May 9, 2019 at 16:57
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    They cannot change anything they already experienced, their past is fixed. they can change things that will affect their future experiences such as old Captain America showing up after the time travel was done. Commented May 10, 2019 at 2:00
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    @TheFallen according to the writers yes, the directors would disagree.
    – TheLethalCarrot
    Commented Apr 25, 2020 at 12:24

In Captain America: The First Avenger we learned that he can't get drunk due to the fact that with the Super Soldier Serum, his metabolism is increased 4 times and that the Serum is attached to his DNA cells, it prevents his cells from deteriorating as said by him,

Steve Rogers: Dr. Erskine said that the serum wouldn't just effect my muscles, it would effect my cells. Create a protective system of regeneration and healing. Which means, um, I can't get drunk. Did you know that?

Peggy Carter: Your metabolism burns four times faster than the average person. He thought it could be one of the side effects.

So with a lot of thought on my behalf I do not fully understand why he aged in Avengers: Endgame.

But another theory that I think is possible is that since he was in the ice for nearly 70 years, his cells were,like him, "frozen in time". And then when he came out of the ice, his cells very slowly started to degenerate but did not make a huge physical appearance.

But when he went back to return the Stones and made the decision to stay with Peggy (in around the 1940's), he did not have to crash the plane into the Atlantic and he went on that date with Peggy, so his cells continued to very slowly degenerate which allowed him to age around 106 years once he returns to the original timeline, in 2023 after defeating Thanos.

  • Your last paragraph is assuming that he somehow magically melded with the young Steve Rogers, which is implausible.
    – Möoz
    Commented Aug 3, 2020 at 4:09

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