When the Semites arrived in Mesopotamia, they found not only Sumerian and Elamite, but also the substrates of these languages, called Proto-Euphratean or Proto-Tigridian, about which nothing is known. In the north, Akkadian competed with Hurrian.
Akkadian took many loan words from Sumerian. In the long run, however, Akkadian, first in the period of Middle Babylonian and then increasingly in New Babylonian, becomes the lingua franca for trade and diplomacy in the Near and Middle East, from Tell-el-Amarna in Egypt to Hattusha in Asia Minor and to Elam in Persia, and ousts most of its former neighbors.
From the -7th cent. on, Aramaic appears in the region. From the middle of the millennium on, it starts to oust Akkadian (Babylonian) as a spoken language. In the western part of the Achaemenide empire (from -539 on), it is used as an administrative language.