At the beginning of the third millennium BC BC, the first cultivated government known as Ilam was established in the Susiana Plain or today Khuzestan.
The residents of Susa (the current Shush) used their invented Proto-Elamite alphabet. The Ilam area extended from the south and southeast toward the center of the Iran plateau. Before arriving of the Medes and Persians in the first millennium BC, the history of Iran was just Ilam history. Our information about other regions and territories in Iran during this period is exclusively from Babylonian tablets (in which they described the governments and neighboring states of Babylon) from archaeologists' discoveries.
The groups scattered in different parts of Iran from south to north were the Elamites, Kassites, Lullubi, and Guti, all of whom had a descendant of a single tribe. Remnants of an ancient civilization were recently discovered in the burnt city near Zabol and date back to 3500 BC. Meanwhile, the people of Shahdad and Tappeh Yahiya had advanced civilizations before the arrival of the Aryans on the Iranian plateau.