dates from the Second Dynasty (28th or 27th century BC). There are around 800 hieroglyphs dating back to the Old Kingdom, Middle Kingdom and New Kingdom Eras. By the Greco-Roman period, there are more than 5,000. Writing was very important in maintaining the Egyptian empire, and literacy was concentrated among an educated elite of scribes. Only people from certain backgrounds were allowed to train to become scribes, in the service of temple, pharaonic, and military authorities. The hieroglyph system was always difficult to learn, but in later centuries was purposely made even more so, as this preserved the scribes' status. The world's oldest known alphabet appears to have been developed by Canaanite turquoise miners in the Sinai desert around the mid-19th century BC. Around 30 crude inscriptions have been found at a mountainous Egyptian mining site known as Serabit el-Khadem. This site was also home to a temple of Hathor, the "Mistress of turquoise". A later, two line inscription has also been found at Wadi el-Hol in Central Egypt. Based on hieroglyphic prototypes, but also including entirely new symbols, each sign apparently stood for a consonant rather than a word: the basis of an alphabetic system. It was not until the 12th to 9th centuries, however, that the alphabet took hold and became widely used. Elamite scripts Over the centuries, three distinct Elamite scripts developed. Proto-Elamite is the oldest known writing system from Iran. In use only for a brief time (c. 3200–2900 BC), clay tablets with Proto-Elamite writing have been found at different sites across Iran, with the majority having been excavated at Susa, an ancient city located east of the Tigris and between the Karkheh and Dez Rivers. The Proto-Elamite script is thought to have developed from early cuneiform (proto-cuneiform). The Proto-Elamite script consists of more than 1,000 signs and is thought to be partly logographic. Linear Elamite is a writing system attested in a few monumental inscriptions in Iran. It was used for a very brief period during the last quarter of the 3rd millennium BC. It is often claimed that Linear Elamite is a syllabic writing system derived from Proto-Elamite, although this cannot be proven since Linear-Elamite has not been deciphered. Several scholars have attempted to decipher the script, most notably Walther Hinz and Piero Meriggi. The Elamite cuneiform script was used from about 2500 to 331 BC, and was adapted from the Akkadian cuneiform. The