How do scholars date the Vedas, and why is it still argued about?

Scholars date the Vedas from internal evidence and from outside evidence, and the result is a range, not a single year. The bulk of the Rigveda was composed in the Punjab, most likely between about 1500 and 1200 BCE, though a wider estimate of 1700 to 1100 BCE has also been given. The other three Samhitas date to about 1200 to 900 BCE.

One of the best outside anchors is not in India. The earliest written evidence for an Indo-Aryan language is found in northern Syria, in the Mitanni kingdom, whose kings took Old Indic throne names and used Old Indic terms for horse-riding and chariot-driving. Michael Witzel points to Mitanni material of the 14th century BCE as the only epigraphic record of Indo-Aryan contemporary to the Rigvedic period.

Language is the second clue. Accumulated linguistic evidence points to the Indo-Aryan languages as intrusive into the subcontinent some time in the 2nd millennium BCE. Genetics adds a third: ancient DNA comparisons reveal a significant infusion of male Steppe ancestry in the second millennium BCE.

The word "invasion" is now used only by opponents of the migration theory. Mortimer Wheeler once famously said the god Indra "stands accused" of destroying the Indus civilisation, but that position was discarded after no evidence of wars was found. Later 20th-century scholarship saw migration and acculturation as the means by which Indo-Aryans and their culture spread into northwest India around 1500 BCE.

Why is it contested? Because the dating carries modern weight. The Rigveda plays a role in the modern construction of a Hindu identity: in the "Indigenous Aryans" and Out of India theories, dating it as early as, or earlier than, the Indus Valley civilisation supports an argument that this civilisation was Aryan. Hindutva opponents of the migration model promote Indigenous Aryanism, the claim that speakers of Indo-Iranian languages are indigenous to the subcontinent. It has no support in contemporary mainstream scholarship, as it is contradicted by a broad range of research and evidence on Indo-European migrations.