The single most remarkable fact about the Rig Veda is not its age but its condition. It was transmitted orally, and the tradition built engineering to stop it drifting.
Students first learn the samhitapatha, the continuous text with all the euphonic joins of sandhi applied. They then learn the padapatha, the same text with every word separated out and every compound resolved, an analysis, in effect, that fixes the word boundaries the continuous recitation blurs. On top of that sit the permutation recitations. Kramapatha takes words in overlapping pairs. Jatapatha braids each pair forwards, backwards and forwards again. Ghanapatha, the hardest of the eleven recognised styles, weaves groups of three in a fixed pattern of reversals. Every word is thereby recited in several different neighbourhoods, so a slip in one position is exposed by the others, and the pitch accent, which classical Sanskrit lost, is preserved with it.
The result is a text whose recensions across the whole subcontinent differ by remarkably little, at a distance of three millennia. The manuscript record, by contrast, is thin and late: the oldest surviving copies, from Nepal, are of about 1040 CE, some two and a half thousand years after composition. Writing arrived in India long before then, and was deliberately not used for this. Recitation was the ritual act; a written Veda was, in some formulations, no Veda at all.
The first printed edition was Friedrich Max Muller's, issued at Oxford between 1849 and 1874 with Sayana's fourteenth-century commentary. UNESCO proclaimed the tradition of Vedic chant a Masterpiece of the Oral and Intangible Heritage of Humanity in November 2003, by which time the number of reciters holding a full Veda in the harder styles had fallen sharply.