Undeciphered writing systems
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An undeciphered writing system is a written form of language that is not currently understood.
Many undeciphered writing systems date from several thousand years BC, though some more modern examples do exist. The term "writing systems" is used here loosely to refer to groups of glyphs which appear to have representational symbolic meaning, but which may include "systems" that are largely artistic in nature and are thus not examples of actual writing.
The difficulty in deciphering these systems can arise from a lack of known language descendants or from the languages being entirely isolated, from insufficient examples of text having been found and even (such as in the case of Vinča) from the question of whether the symbols actually constitute a writing system at all. Some researchers have claimed to be able to decipher certain writing systems, such as those of Epi-Olmec, Phaistos and Indus texts; but to date, these claims have not been widely accepted within the scientific community, or confirmed by independent researchers, for the writing systems listed here (unless otherwise specified).
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.
- Jiahu symbols – Peiligang culture, from China in the 7th millennium BC.
- Vinča symbols – Neolithic Europe, from Central Europe and Southeastern Europe in the 6th millennium BC.
- Dispilio Tablet – Neolithic Europe, from Greece in the 6th millennium BC.
- Banpo symbols – Yangshao culture, from China in the 5th millennium BC.
Bronze Age scripts
The following is a list of undeciphered scripts from the Bronze Age (3300 to 1200 BC).
- Indus script – from c. 3500 BC.
- Proto-Elamite – Elam, from c. 3200 BC.
- Linear Elamite, from c. 2200 BC.
- Linear A, from c. 1900 BC, a syllabary.
- Cretan hieroglyphs, from c. 1900 BC.
- Cypro-Minoan syllabary, from c. 1500 BC.
- Phaistos Disc, c. 2000 BC.
- Wadi el-Ħôl script, c. 1800 BC, likely an abjad.
- Byblos syllabary – the city of Byblos, c. 1700 BC.
- Southwest Paleohispanic script, from c. 700 BC.
- Sitovo inscription, probably Phrygian.
- Ba–Shu scripts, 5th to 4th century BC.
- Issyk inscription (ancient Turkestan and Afghanistan)
- Khitan scripts – Khitan, 10th century, not fully deciphered.
- Kohi script - (Gandhara, 3rd century BC to 8th century AD)
- Tujia script
Many Mesoamerican writing systems have been discovered by archaeologists. Many of them remain undeciphered due to a lack of knowledge of the original language. These writing systems were used between 1000 BC and 1500 AD.
- Olmec – Olmec civilization, c. 900 BC, possibly the oldest Mesoamerican script.
- Isthmian, c. 500 BC, apparently logosyllabic.
- Zapotec – Zapotec, c. 500 BC.
- Mixtec – Mixtec, 14th century, perhaps pictographic.
South American scripts
- Quipu – Inca Empire, 15th century, thought by some to have been a writing system, but generally believed to be an accounting system.
Medieval and later scripts
- Dandaleith stone
- Alekanovo inscription
- Rohonc Codex
- Singapore Stone, a fragment of a sandstone slab inscribed with an ancient Southeast Asian script, perhaps Old Javanese or Sanskrit. At least 13th century, and possibly as early as 10th to 11th century.
- Voynich manuscript, carbon dated to the 15th century.
- The Newton Stone, which is considered by many scholars to be modern forgery
- Some scholars consider the corpus of Pictish symbol stones to be an undeciphered writing system
- So-called Hamptonese, a language used by outsider artist James Hampton in his presumably religious text. 
Related concepts: texts that are not writing systems
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 particularly include asemic writing created for artistic purposes. One prominent example is the Codex Seraphinianus.
Another similar concept is that of undeciphered cryptograms, or cipher messages. These are not writing systems per se, but a disguised form of another text. Of course any cryptogram is intended to be undecipherable by anyone except the intended recipient so vast numbers of these exist, but a few examples have become famous and are listed in the undeciphered historical codes and ciphers category.
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