The details of how Captain America (Chris Evans) survived being frozen in ice for 66 years have been revealed by Marvel. Introduced in 2011's Captain America: The First Avenger, Steve Rogers is one of the greatest heroes of the Marvel Cinematic Universe and he's the Living Legend of World War II. Tragically, Captain America lost six decades of his life due to being cryogenically frozen in ice after he stopped the Red Skull (Hugo Weaving) from attacking America.
Of course, Captain America's story didn't end in 1945 and his heroism became even more legendary after he was revived and became the leader of the Avengers. Along with the other heroes assembled by start a new life with his eternal love, Peggy Carter (Hayley Atwell).
Peggy was the last person to hear Steve's voice when he went down into the ice, and everyone assumed Captain America was dead for six decades before he was found in the ice by SHIELD in 2011. But the reasons why Rogers survived in the ice for so long - perfectly preserved and not having aged at all - were finally revealed in the new book The Wakanda Files: A Technological Exploration of the Avengers and Beyond, which was compiled in-universe by Shuri (Letitia Wright). The Wakanda Files contain an encrypted SHIELD message sent by Agent Phil Coulson (Clark Gregg) to Nick Fury after he oversaw the arrival of Captain Rogers, who Coulson referred to as "the anomaly", at SHIELD's base in New York City.
In his communique, Coulson stated the SHIELD team's findings of Captain America's physical condition: "Happy to report that he's healthy; vitals should stabilize shortly after the thawing process. He doesn't look to have aged a day since 1945. Medical attributes this to his blood having thickened during the flash-freezing process but not having completely frozen through. Essentially, they believe that Erskine's serum, his increased metabolism, and his increased immune system put him into a cryogenic hibernation."
Back in 1943, Steve Rogers was, of course, one of the first recipients of Dr. Abraham Erskine's (Stanley Tucci) Super-Soldier Serum (after a prior botched infusion into the Red Skull). Along with Steve's sickly frame being infused by vita-rays, the Super-Soldier Serum transformed Rogers into a physically perfect form with superhuman attributes. Captain America's strength, speed, and ability to shrug off injury are well-known to fans, but Coulson's rundown of how Rogers survived being cryogenically frozen speaks to the other, unseen benefits of Erskine's miracle tech.
Captain America's blood and metabolism not only prevent him from illness but they were also instrumental in Steve being able to emerge from 66 years in the arctic ice in perfect physical condition. Not only did the Super-Soldier Serum enable Captain America to survive being frozen in ice but it also allowed Steve to live an extraordinarily long time, so that he was able to have an entire lifetime with Peggy Carter after he time traveled in Avengers: Endgame.
