History of Decipherment of Proto-Elamite
Proto-Elamite is still largely undeciphered, although a majority of the material has been abailable for study for more than three quarters of a century.
Early work on proto-Elamite centered around comparing individual signs with signs from the neighboring cuneiform writing system. It has since been conclusively shown that a graphical similarity between signs from two writing systems is not proof of a semantical similarity.
For a variety of reasons it has been argued that proto-Elamite was used to write Elamite, a language which is first attested around 2300 BC. This cannot be proven at present, although it is of course a possibility. However, the earliest proto-Elamite tablets, if not all, were in fact language neutral. Although this is not the same as suggesting that they could be read by anyone, it means that they were not coding speech.
Since the publication of Jöran Friberg's groundbreaking study, concerning ancient Near Eastern metrology, in the seventies, the decipherment of the world's earliest writing systems has been moving steadily away from a traditional linguistic research mapping individual signs in complex strings onto the grammatical elements of a spoken language, and into the realm of history of science and related fields.