Before we discuss the probable range of dates for the Rigveda based on the massive multi disciplinary evidence collected in the last twenty years, we will give the dates given in text books of Indian history authored by Indians and others.
Max Muller assigned the period 1500 BCE to 500 BCE for Rigveda Samhita. One of the reasons given is that beginnings of human kind cannot be earlier to 4000 B.C.E. Since the evidence was flimsy, he recanted his earlier assignment near the end of his life. However, many Indian historians still believe in this assignment. According to these persons, all the Veda Samhitās were not composed in India. They were composed by members of tribes, the so called Aryans, who invaded India from the Northwest, destroyed the old civilisation in the Indus Valley, supposedly Dravidian, and drove out these original inhabitants to the south of India and other parts. The ruins of this early Indus Valley civilisation dated 3000 BCE are at Harappa and Mohenjadaro which are dated 3000 BCE or earlier. This Aryan invasion theory was proposed by the British archaeologist Wheeler around the early part of the twentieth century.
It is said that the battles between Indra and Dasyus in the Rigveda are really the battles between the Aryans and the native Dravidians of the Indus Valley. Rigveda has no mention of the word dravida. It has a word anaāsa noseless referring to the demons or dasyus. Some scholars identify these dasyu with the Dravidians since Dravidians supposedly do not have prominent noses!
The motivation for the British administrators in India to include the invasion theory in history books should be clear. Indians who descended from the Aryans should not complain against the British rule since they themselves are immigrants and hence they have no more Right than the British to rule India.
This theory has several major drawbacks. First of all ārya in the Veda means a noble person, not the name of a tribe. RV (9.63.5) states, “make all of us in the universe ārya, noble”. As observed earlier, the battles in the Rigveda do not occur on earth, but in the atmosphere or the subtle planes; they are battles of the devās, the powers of Light versus the demons, the Dasyus, the powers of ignorance. To regard these battles as between two different human tribes, we have to eliminate ninety percent of the Rigveda which contains detailed description of the devās as supraphysical forces of Light and those of Dasyus as the forces of ignorance.
Finally all the modern archaeologists like Shaffer declare that there is no archaeological evidence for such an invasion; the invasion is a myth propagated by historians. Thus the suggested date 1500 BCE-500 BCE has no support at all.
Now we will discuss the date of Rigveda from all the available multidisciplinary evidence, some of which were collected in the last decade, some others known earlier.
Let us first consider the satellite photography studies of the Indus Valley. The Sarasvati described in Rigveda is a massive river, located between Yamuna and Shutadrī (Sutlej) flowing into the ocean. The satellite studies indicate this river as completely dried up by the date 1750 BCE. The Satellite study cannot refer to the Sarasvati (Haraquiti) river in Afghanistan since it is a small river that dries up in the desert. Thus the lower bound for the Vedic civilisation is 1750 BCE. It is more ancient than this date because Rigveda does not mention any desert; it is mentioned in the Brāhmaņa books – Shatapatha Brāhmaņa – which is at least 500-1000 years later than Rigveda Samhita.
The knowledge of mathematics in Rigveda and related texts is another important evidence. Rigveda not only mentions the decimal number system for integers but also the infinity. It mentions in detail the spoked wheel with arbitrary number of spokes (1.164.13,14,48). Clearly such verses would imply that these authors knew the associated mathematical properties of circle and square. The algorithm for circling the square needed for making the spoked wheel is given in the Baudhāyana Shulba Sūtra which is the oldest of the Shulba Sūtrās, ancient mathematical texts dealing with the methods for the construction of altars needed in Vedic rituals and other related mathematical topics. These books are later than the Rigveda Samhita. Even though Dutta made a detailed study of these books around 1930 and showed that the theorem attributed to Pythogoras is contained in these books in a more general form, the western indologists like Keith (or Whitney earlier) did not pay much attention since they were convinced, without any proof, that all the sciences in ancient India – mathematics, astronomy etc., were borrowed from Greeks or Egyptians. It was in 1962 that the American mathematician Seidenberg showed that, “the elements of ancient geometry found in Egypt and Babylonia stem from a ritual system of the kind found in Shulba Sūtrās.” The Shulba Sūtrās contain the algorithm for building the pyramid shaped funeral altar (smashāņa chit). Recall that the Egyptian pyramids are used as tombs for the dead. There is no ancient Egyptian literature for the detailed construction of these pyramids. Hence it is more than likely that their source is the Shulba Sūtrās. This piece of evidence fixes the date for the Baudhāyana Shulba Sūtra which gives a lower bound date for Rigveda.
Next let us consider the astronomical evidence. Rigveda and all other ancient books contain several statements of astronomical significance like the position of Sun in the Zodiac on the two equinoxes, vernal or spring equinox and autumn equinox. Indian Astronomy is based on sidereal Zodiac. The Zodiac is divided into 27 roughly equal segments, all are measuring 130 20′ of arc. The seventh mandala of the Rigveda records the vernal equinox in Mrigashira Constellation pointing to a date around 4000 BCE – a fact noted by Jacobi and Tilak. Again several Shulba Sūtrās declare that a pole star is visible. Since a visible pole star occurs only at certain epochs, such a citation gives a normal range of dates for that event. There is much more information beyond the scope of this paper.
Next we consider the Harappa culture. Findings tested with calibrated C-14 methods show that, “the Harappa culture should be dated to the period 2700-2000 BCE with a terminal date not lower than 1900 BCE, a date suggestively close to the drying up of Sarasvati”. It was a fashion for the historians to declare that the Harappa Culture had no connection with the culture of the Vedic era. Now things are beginning to change. In one of the seals of the Harappa period, there is a picture of a bull with one horn. It was called as a unicorn. But the Sanskrit epithet, eka shŗngaĥ, one with a single horn, is a common epithet for Lord Shiva in the Veda Samhitās [RV 7.19.1] and the bull is always associated with Shiva. There is a seal of a meditating person in a sitting lotus pose in the Harappa seals. On the Harappan seals, there are inscriptions in a script which was not deciphered for a long time. Recently N.K. Jha has suggested a deciphering approach which is very promising. The language is syllabic like all Indian languages, the script seems to be close to old Brahmi. The researcher Jha has identified the inscriptions on several seals, which appear to be words from the lexicon of Vedās, nighantu published by Yaska, the first commentator on Rigveda and a lexicographer. So Harappa civilisation presents the end of the Vedic period.
Again Rigveda does not mention either silver or cotton. Since the date of cotton is well established, again we get a lower bound on the Rig Vedic date.
Now the evidence can be summed up and some range of dates can be given. Rigveda repeatedly refers to ancient sages and modern sages as in (1.1.2). The age associated with these ancient sages can be called as the high Rig Vedic period which is declared to be 3100 BCE or early. This period 3700-3800 BCE is the closing of the Rig Vedic age, especially the Mandalas seven and third associated with the sages Vasişhţa and Vishvāmitra. The Shulba Sūtrā texts of Baudhāyana, Ashvalāyana etc., can be dated 3100-2000 BCE; 1900 BCE is the drying up of Sarasvati and the end of Vedic age. The Vedic civilisation ended, as indicated by the Harappa ruins, due to ecological causes, draughts and desertification. There was no invasion by any one.