WARNING: Major spoilers for Avengers: Endgame.
Even though Avengers: Endgame did not feature any X-Men characters, it may have secretly included a way for mutants to be brought into the Marvel Cinematic Universe. For the first eleven years of the MCU, Marvel Studios has been unable to use the X-Men and Fantastic Four. The MCU has performed just fine focusing on Iron Man, Captain America, Thor, and others, but many have been interested to see if, how, and when the X-Men could one day be brought within the massive shared universe.
This is now possible thanks to Disney's acquisition of Fox, which is expected to result in a complete reboot of all Marvel characters previously owned by Fox, except for Ryan Reynolds' Deadpool. However, the deal did not close until earlier this year and left Marvel Studios with little time to add references to mutants, the Baxter Building, or any such Easter eggs to Avengers: Endgame. This was for the best though, as the movie was allowed to focus on the story at hand, and since the X-Men may not be fully introduced into the MCU for several more years.
The integration of mutants may not be the primary focus of Marvel Studios head Kevin Feige right now, but they are no doubt beginning to think how this sudden addition could be possible. Thanks to a major moment at the beginning of Avengers: Endgame, they may now have the perfect way to bring them into the fold - even if this wasn't intended.
Thanos' Second Snap Destroyed The Infinity Stones - And Released A Lot Of Cosmic Energy
At the very beginning of Avengers: Endgame, the remaining heroes are all trying to figure out what their game plan is going to be to try and stop Thanos. They agree that the best plan is to go on the attack and kill the Mad Titan, taking the Infinity Stones for themselves so they can undo what he's accomplished. Nebula reveals that he would go to his garden, which Rocket is able to locate by finding an energy signature that is as high as the one that hit Earth when Thanos snapped his fingers originally in Avengers: Infinity War.
But, when they arrive to the garden and think they've won after cutting off his hand, they discover that the Infinity Stones have been destroyed after Thanos performed a second snap. This is a big deal as far as the plot of Avengers: Endgame is concerned, as it eventually turns the heroes towards time travel, but it is could also be the key to unleashing mutants. Destroying the stones with another snap released an incredible amount of cosmic energy, and possibly even the power of the Infinity Stones as they were reduced to atoms. The combination of this power could be how the X-Men are created in the MCU.
One of the most popular aspects to theories on how the MCU will introduce the X-Men is through the idea of latent X-genes being activated. This has already possibly been done before in-universe, as Marvel Studios' Visual Dictionary previously hinted that Scarlet Witch received her powers as a result of the Mind Stone "unlocking something latent inside her," and this would theoretically be the same for Quicksilver too. We've previously theorized that Scarlet Witch and Quicksilver could be two of the first mutants in the MCU after an eventual retcon, and thanks to the various snaps in Avengers: Infinity War and Avengers: Endgame, this may now be able to be applied across the entire galaxy.
Could Thanos Have Awakened The Mutant Gene With The Snap?
The second snap specifically could be the key to the expansion of the X-Men in the MCU. The cosmic energy that the second snap gave off could scatter the power of the Infinity Stones across the galaxy. If this did happen, then anyone could unknowingly be hit with the combination of cosmic energy and Infinity Stone atoms and then see their own latent X-genes be activated. This would be a great move too, as it could instantly help establish cosmic X-Men in the MCU.
Back on Earth though, this same energy and atoms could potentially reach humanity and begin the activation of dormant X-genes. However, there were also three other snaps that took place on Earth, which would make it the home to a high concentration of cosmic energy. These snaps may not release the full power of the Infinity Stones, but any energy they create is still generated from them. This could mean that after the second snap activates X-genes around the universe, these additional snaps could give off enough energy to awaken more. Plus, as Earth is sure to be the home of many mutants in the MCU, using these other snaps to awaken additional X-genes could explain why Earth (of all places) has a large mutant population.
As far as Marvel Comics has explored, the snapping of someone's fingers has never been the cause of an increase in the mutant population, but something akin to cosmic energy has. The 2012 Avengers Vs. X-Men event saw a blast of Phoenix Fire cover Earth and activated dormant X-genes across the globe. The same thing could happen here, but using the cosmic energy of the snaps being the inciting incidents, and the multitude of them increasing the amount of transformations.
Thanos Creating The X-Men Post-Snap Would Create A New Mutant/Human War
Thanos being the catalyst for the X-Men's introduction in the MCU would not only be a great way to tie their awakening into the larger story, but could also be a reason why mutant and human-kind would not see eye-to-eye. A certain amount of public disdain for the X-Men has always been key to how they are portrayed in the comics, as they've usually been a symbol for oppression, racism, and more. But, in a world where the Avengers are the biggest celebrities on the planet and people with powers are usually seen as heroes, it is difficult to find a reason why mutants would not receive the same treatment in the MCU.
But, if the birth of the X-Men in the eyes of many is linked to Thanos in any way, then the resentment towards him could then be passed along to the X-Men. People in the MCU are undoubtedly happy to see that their loved ones are back alive, but having these new powered people literally be the result of Thanos' actions could easily make them disliked, whether by the majority or just a vocal minority. This could change over time, but mutants being created as a result of Thanos and the most horrific event that the galaxy has ever seen does immediately put them in a position where they could be at odds with the rest of humanity.
Other Potential X-Men Origins In Avengers: Endgame
Even if the snaps do not result in the creation of mutants, Avengers: Endgame teases a few other X-Men connections. One quick line of dialogue from Okoye may be teasing Namor existing in the MCU, and he is oftentimes referred to as Marvel's first mutant. His mutant genes may have already been activated or not be part of the character in the MCU if he and Atlantis are already underwater though, but there's another mention that could also be setting up the X-Men.
Peggy Carter references someone by the name of Braddock during one of her scenes, and even though many have taken this as a tease that Brian Braddock aka Captain Britain is alive and getting his powers in 1970, it could also set up a future X-Men. Whether this Braddock is Brian or possibly his father James, the Braddock family also features Betsy Braddock, who is a mutant better known as Psylocke. It is unlikely that she is the agent in question during this scene, but her father or brother being involved may also establish her own entry to the MCU, once the rest of mutant-kind is introduced.
Whether or not this theory turns out to be true or any of these hints in Avengers: Endgame come to pass, it is clear that Marvel Studios has plenty of options at their fingertips to introduce the X-Men. They could even do a reverse House of M storyline and have Scarlet Witch bring the mutants into being. Since it isn't clear what Marvel Studios will do, we'll just have to wait and see what they decide.
