Interpreting the raising of the eyebrows to mark a question in American Sign Language:
In the sign languages of the deaf, facial movements and expressions often serve syntactic functions. For example, in American Sign Language, a declarative sentence is converted into a question if accompanied by a forward movement of the head and shoulders, and a raising of the eyebrows. Relative clauses are signaled by a raising of the eyebrows and upper lip, with the head tilted back. An affirmative sentence becomes a negative one if accompanied by a shaking of the head. (Examples are from Neidle et al. 2000.) Of course, sign language does not necessarily resemble any gestural language that our ancestors, such as Homo erectus, may have used. It is nevertheless interesting that facial gestures should generally convey syntax, whereas manual gestures supply content. As suggested earlier, syntax may have been grafted onto gestural communication from around two million years ago with the emergence of the genus Homo. If syntax was predominantly facial, this suggests a progression from manual to facial gesture in the emergence of language.
Michael C. Corballis, "From mouth to hand: Gesture, speech, and the evolution of right-handedness," Behavioural and Brain Sciences (2003) 26, 199–260, p. 203.
The prelinguistic raised-eyebrow gesture may not itself be particularly meaning specific, but pragmatic considerations surrounding the communicative interchange would contribute to its being inferred as a gesture indicating interest or intentness, or that some information is being solicited, akin to a question being asked. This prelinguistic gesture—available to both deaf and nondeaf communities in North America—is also used as a grammatical yes-no question marker in ASL, however. In this grammatical context it is specific in meaning, marking any string as a yes-no question. Thus a prelinguistic gesture has been recruited as a grammatical marker, and it would be difficult to claim that either is a lexical item in the sense of a content word. In this case, it appears that a grammatical marker, albeit a rather iconic one, takes as its source a more general communicative gesture, with no lexical word developing or intervening at this stage of grammatical development or later. . . .Terry Janzen and Barbara Shaffer, "Gesture as the substrate in the process of ASL grammaticization," in Modality and Structure in Signed and Spoken Languages, pp. 199-223p. 214.
Raising the eyebrows primordially expresses inter-est, an opening of the person to coexistence, or, to be specific, the person-to-person world. The question along with its precursors is prominently interpersonal, as if we related to being-together first through concrete personhood.
Lets play for a moment with the nonlexicality of the question, or the nonlexical inflection of the question itself. What is, after all, the content of a question in general? Is the question something we graft on to other meaningful utterances, something that thrives only by being grafted on to other expressions, a style that must be added, a doubling of expression, a twist? Is it itself a hybrid, or does it represent a process of hybridization? Or does it represent, in particular, which can be inferred from its nonlexical mode of expressing interest, an originary interpersonalization of meanings? Or likewise a giving of meaning to the interpersonal? What is Sinngebung in its nonlexical mode? (Assuming it has one. I would tend to assume that there is a prelexical mode of the Logos, whether it be accessed in the complete absence of words, or, on the contrary, only through words, perhaps through an abandonment of words. I'm open to criticizing this assumption.)