A mysterious script could help solve the mysteries of one of humanity's oldest civilizations.

The Indus River Valley civilization site is as important to archaeologists as ancient Mesopotamia and ancient Egypt. Covering an 500,000 square mile region along the Indus River and its tributaries in Pakistan and northwestern India, the Indus civilization included more than 1,000 settlements.

Most of these settlements were villages, some were towns, and at least five could be considered cities during the civilization's peak from 2600-1900 B.C. The largest of these cities were Mohenjo-daro and Harappa, which were marvels for their time.

The cities had complex street planning, covered sewer systems, and the world's oldest toilets. And amazingly, there's no archaeological evidence suggesting war or armies in the Indus River Valley civilizations. Although the Indus civilization was hardly a violence-free society, archaeologists have yet to discover stockpiles of weapons, art depicting war, large-scale structural destruction, or the telltale layers of ash under cities that have been burned to the ground during battles.

While they weren't warmongering, they weren't cut off from others either. Evidence of trade with other more warlike civilizations like Mesopotamia has been found. A Harappan trade outpost was discovered in the Mesopotamian city of Eshnunna, about 20 miles outside of Baghdad, and Harappan luxury goods have been found in other Mesopotamian cities like Ur.

But the Indus civilization is also known for their still undeciphered scripts, which were carved into smooth stones used as seals, terracotta tablets, and some metal objects.

These partially pictographic scripts feature humans and animal motifs, but their meanings and organization are still a mystery. Until we crack the script there are still many unanswered questions about this mysterious civiliation.

There are three main obstacles standing in the way of translating the Indus scripts.

First, no concrete information is available about the underlying language of the script. In the past we've been able to dissect formerly undecipherable languages using comparable modern languages. The mysterious Linear B script turned out to be written using an archaic form of Greek and Mayan glyphs were deciphered using current spoken forms of Mayan.

But a contemporary connection to the Indus script isn't as clear, and politics further complicate the matter of using one if it does exist. Some Indian scholars claim the scripts can be read with an ancestral form of Sanskrit, itself the language most northern Indian languages, like Hindu, are based on.

The problem is that this could have implications for Hindu nationalist politics, as it would support the controversial view that there has been a consistent Sanskrit-speaking national identity in India dating back 5,000 years. But the Indus script could just as easily be related to other Indian language families, like the southern Indian Dravidian (which includes Tamil) family.

Second, the scripts feature no specific people that can be cross referenced with myths or historical records in other texts. For instance, the Egyptian pharaoh Ramses is mentioned in Greek texts describing the ancient Egyptians.

Not so for the Indus scripts. In addition to the lack of war, one of the lasting mysteries of the Indus civilization is the distinct lack of references to great leaders in the society.

Finally, we haven't found a bilingual translation tool, like the Rosetta Stone, for the Indus script.

The Rosetta Stone, written in both ancient Egyptian and Greek, was key in deciphering Egyptian hieroglyphics. But just because we haven't found a Indus equivalent doesn't mean researchers have given up hope. A linguistic bridge connecting the Indus Script to another known language could reside in one of Mesopotamian cities that traded with the Indus civilization.

There are have been more than 100 attempts at deciphering the Indus script published since the 1920s, and just how many signs are in the script is still up for debate. A sign is a basic unit of meaning in languages — they can represent freestanding ideas or syllables.

One decipherment was published in 1982 by Indian archaeologist Shikaripura Ranganatha Rao claimed the script was Sanskrit-based and contained only 62 signs. In 1994, though, Finnish Indologist Asko Parpola estimated 425 signs, a claim that was supported by Iravatham Mahadevan, the leading Indus script researcher in India.

As Andrew Robinson of Nature points out, most researchers believe that there are too many signs in the Indus script for it to be an alphabet or a syllabary (where signs represent syllables). Instead, it's probably a logo-syllabic script, a mix of hundreds of symbols for words and concepts (think $ and %) and a smaller number of signs that represent syllables.

While the Indus script is still far from being deciphered, the evidence favors the theory that the script is written in a proto-Dravidian language. Researchers have been able to decipher the meaning of some groups of signs using Old Tamil (part of the Dravidian language family).

Less than 10% of the identified Indus River Valley sites have been excavated, though, so hopefully more research will reveal more about this mysterious script.

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