Rig Veda 11,000 Years Old. Sarasvati River Research Satellite Images Dhola Vira Site

Dhola Vira is dated ,at least, to about 4,500 years ago,according to Archeologist  Sri. Bisht

The well deveoped structures and advanced water storing wells indicate a civilization which has been there for quite sometime.

The answer lies in the river Saraswathi.

Sky Maps Star Position During Rig Veda Rama Krishna Birth

This is the earliest reference to Vedic calendar with year beginning at Winter Solstice, found in Rigveda (5-77-1/2; 1-46-14; 7-69-3/2). Heliacal rising of Ashwini Nakshatra (Aries) can be seen to occur on 5th January, 7000 BC, marking the year beginning (Fig. 1)…The Sky of 19th December, 6000 BC at sunrise on the Winter Solstice day shows that Ashvini gave way to bright star Chitra (α Vir) on opposite side (Western horizon). A full Moon in Chitra Nakshatra provided a new time marker in the sky and heralded the lunar month naming system-Chaitra, Vaisakha etc. (Rigveda: 5-74-1,2 and Tait Samh. 7-4-8).

Break In Eternity Vedas Dates Rishis Mantras

If the Purana, Ithihasas are later than the Vedas, how come they are mentioned in the Vedas?

It is also stated that Viswamitra gave the world the Gayatri Mantra, to whom it was revealed.

The Rig Vedic version has one syllable short and Taittriya Aranyaka has the full detailed version.
Does this mean that before it was revealed to Viswamitra no body chanted it?