The main factor in the expansion of Aryan culture during the later Vedic period was the introduction of iron around 1000 BCE. The Rigvedic people knew of a metal called ayas which was either copper or bronze. In later Vedic literature, Ayas was equated with Shyama or Krishna meaning black to represent iron. Archeology has shown that iron began to be used around 1000 BCE, which is also the period of later Vedic literature.
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