Certain forms of proto-writing remain undeciphered and, because of a lack of evidence and linguistic descendants, it is quite likely that they will never be deciphered. See more

South Asia
• Indus script, c. 3500 BC to 1900 BC.
• Vikramkhol inscription, c. 1500 BC.
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• Rongorongo – Rapa Nui. After 1200, before 1860. Probably logosyllabic.
• Rongorongo See more

• Proto-Elamite (CDLI link)
• Vinča signs (The Old European Script: Further evidence – Shan M. M. Winn) See more

Andean Region
• Quipu – Inka Empire and predecessor states, like the Wari Empire or the Caral-Supe Civilization, c. 2600 BC – 20th century, with … See more

One very similar concept is that of false writing systems, which appear to be writing but are not. False writing cannot be deciphered because it has no semantic meaning. These … See more