As the culture of the great Indus Valley civilization declines, new languages and cultural orientations are introduced into South Asia by people migrating from the northwest. Settling in the Gangetic Plain, the so-called Aryans interact with indigenous cultures, and their language, Sanskrit, eventually dominates. Beginning around 1500 B.C., the Vedas, hymns in Sanskrit that comprise the earliest Hindu writings, are composed. Settlements also begin to flourish in central and southern India. Ironworking develops in the north around 1300 B.C. and by 1000 B.C. in the south.