Warning: This contains SPOILERS for Black Panther: Wakanda Forever!
Thanks to Namor's introduction in Namor's mutant DNA makes him half-human, half-Talokanil, which is why he is so powerful.
Namor's origin story in Black Panther 2 allows a direct answer for how long mutants have been in the MCU. The movie reveals that Namor's mother was pregnant with him in 1517 before the Yucatan natives began to live underwater. This confirms that mutants have existed in the MCU since at least 1517. Namor is often considered to be the first mutant in the comics, a title that he might now share in the MCU. In any case, Black Panther: Wakanda Forever's Namor reveal confirms that there have been mutants in the MCU for more than 500 years - even though they have not been seen until Phase 4.
Namor Being A Mutant Makes It Much Easier For The X-Men's MCU Introduction
The confirmation that Namor is a mutant and the origin story revealed in Black Panther 2 is a huge help to the MCU's X-Men introduction. There have long been questions and concerns about how Marvel could incorporate the mutants and tie them to the shared universe's past despite them not being shown at all during the Infinity Saga. This has led to various theories about how mutants can suddenly become a bigger part of the franchise, such as Scarlet Witch creating them. But if Namor has been around for over 500 years and remained hidden, Marvel Studios could use a similar reveal for the X-Men's MCU introduction.
While some might take issue with a potential reveal that the X-Men have always been in the MCU, it is the best option that Marvel has. Introducing the X-Men through the multiverse would feel incredibly cheap and having them suddenly be created in the present wipes out a lot of the team's key comic history. Namor living on Earth in secret in Talokan for over 500 years is proof that the MCU's X-Men could also have existed for the last several decades. Marvel could even take a very similar approach and introduce Krakoa as the safe haven where the mutants have been hiding all this time.
Which Other Mutants Already Exist In The MCU?
Namor now becomes the latest mutant to exist in the MCU thanks to Black Panther: Wakanda Forever. Phase 4 has not so subtly continued to introduce mutants to the shared universe. Black Widow's Ursa Major is also a mutant in the comics.
