Scholars are not in agreement as to whether the Kharoṣṭhī script evolved gradually, or was the work of a mindful inventor. An analysis of the script forms shows a clear dependency on the Aramaic alphabet but with extensive modifications to support the sounds found in Indian languages. One model is that the Aramaic script arrived with the Achaemenid conquest of the region in 500 BCE and evolved over the next 200+ years to reach its final form by the 3rd century BCE. However, no Aramaic documents of any kind have survived from this period. Also intermediate forms have yet been found to confirm this evolutionary model, and rock and coins inscriptions from the 3rd century BCE onward show a unified and mature form.