Historians differ as to whether the Elamites could be considered "Iranian". On the one hand, the Elamites spoke a non-Iranian language and were culturally closer to the established civilizations of Sumer and Akkad than they were to the tribes of the Iranian plateau. On the other hand, the Elamites linked the old civilizations of Mesopotamia and the new peoples of the plateau, and their version of Mesopotamian civilization was a formative influence on the first indisputably Persian empire of the Achaemenids. Elam was one of the first conquests of the new Persian empire; Elamite scribes kept the Persians' records, writing them down in Elamite cuneiform. Hence one contemporary historian, Elton Daniel, states that the Elamites are "the founders of the first Iranian empire in the geographic sense". ("The History of Iran", 2001, p. 26). If the Elamites are considered proto-Persians, then Khuzestan would have been one of the cradles of Persian civilization. Many experts such as Sir Percy Sykes in fact called the Elamites "the earliest civilization of Persia" ("A History of Persia", p38), and Ibn Nadeem in his book "al-Fehrest" ("الفهرست"), mentions that all the Median and Persian lands of antiquity spoke one language. In his book, which is the most accredited account of spoken languages of Iran during the early Islamic era, Ibn Nadeem quotes the 8th century scholar Abdullah Ibn al-Muqaffa as having counted "Khuzi" among the Iranian languages and for having identified it as the unofficial language of the royalty of Iran.