The Vedas form a layered archive
The Rigveda belongs to an earlier phase than the Samaveda, Yajurveda, Atharvaveda and later prose and philosophical texts. These works were composed and transmitted orally across generations rather than written at one moment.
Their language, ritual concerns and geography change over time. Historians therefore read the corpus as evidence for several social worlds, not as a single eyewitness account of an entire millennium.
Source: Encyclopaedia Britannica: Rigveda
Iron and agriculture support larger settlements
In the later Vedic period, farming expanded in the western Ganga plain and iron tools became more common. Surplus, craft production and exchange helped some settlements grow into early towns.
The transition was neither uniform nor caused by one technology alone. Archaeological sequences vary by region, and textual descriptions often reflect elite ritual concerns more clearly than ordinary labour.
Source: Britannica: India—The later Vedic period