What sign language does Makkari use?

Question

There are a few facets to this question:

• What sign language is shown in the Eternals film (is it actually ASL, BSL, etc)?
• If it is an actual real-world sign language, are we supposed to infer that the real-world development of the sign language was influenced by the Eternals? Or are we supposed to imagine it is not the actual language they were signing but just a translation for the benefit of the audience, the same way we clearly are not meant to believe they were speaking English in ancient Mesopotamia?
• If it is not a real-world sign language, then who (out of universe) developed the signs and what was it based on?

Answer 1

ASL or American Sign Language was used in the film. The quote below by Lauren Ridloff, the actress for Makkari, makes it seem like ASL was used in universe because it is convenient for the viewer, same with using English, rather than it is actually what happens in universe.

Given the movie’s global and historical scope, were there discussions about the kind of sign language you would be using in the movie?

Yeah, there absolutely was that discussion with Chloé. I know a lot of people don’t realize that sign language is not universal. Each country has their own form of sign language. We have American Sign Language here. There’s also British Sign Language and Mexican Sign Language. I could meet a deaf person from Japan and not understand them, because our sign languages are so different. So we were thinking about Makkari, should we make up some kind of sign language system, because in this story, we start at the dawn of civilization. But Chloé was like, “Look, everybody is speaking English [in the movie]. Come on!” So we decided, why not just use American Sign Language? It makes sense. People haven’t been speaking English since the dawn of time, but here we are.

_{Variety, ‘Eternals’ Star Lauren Ridloff on Playing Marvel’s First Deaf Superhero and the Need to ‘Normalize Subtitles’}