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A statement from a Marvel Studios spokesperson, given to Mashable, defends the hiring, citing both the fictional character’s background and the progressiveness of the Marvel Cinematic Universe as a whole.

“Marvel has a very strong record of diversity in its casting of films and regularly departs from stereotypes and source material to bring its MCU to life. The Ancient One is a title that is not exclusively held by any one character, but rather a moniker passed down through time, and in this particular film the embodiment is Celtic. We are very proud to have the enormously talented Tilda Swinton portray this unique and complex character alongside our richly diverse cast.”

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