AGE OF TAMIL
Stone architecture for temples did not begin in Tamil Nadu until the adventof the Pallava period (600-850 AD). As Dr. JB has pointed out there are other methods to date the people of the Tamil country. We have external evidence from the descriptions of Greek and semitic merchants that traded with the Tamils. But what we need are coins, stone inscriptions, and other written record prior to 500 B.C. We haven't yet discovered them, probably because we are looking for them in the wrong places.
Extensive archaelogical survey is being conducted in the Poompuhar region
(the ancient Chola capital and port city that is submerged in the ocean).
But we may need to look for the Pandiyan capitals of the legends off of
Kanniyakumari coast. But long before the three legendary kings of
the Tamil land ruled, the velir chieftains were leading the Tamils.
We don't really know too much about them.
I have some books on the origin of Tamils that is somewhat dated. I am not sure how much progress has been made since these were published. One is by Prof. V. R. Ramachandra Dikshithar ("Origin and Spread of the Tamils", 1909) and the other is by P. T. Srinivasa Iyengar ( "Pre-Aryan Tamil Culture").
Those who instinctively suspect any work of Tamil brahmins as anti-Tamil propaganda should read these two books and compare it to the works of Vaiyapuri Pillai who went to the other extreme and insisted on dating all Tamil literature as late as possible (late 8th century!)
Tamil history has become an unfortunate battle ground between veda centric scholars (usually smartha brahmanas) and Tamil centric scholars (usually Saiva Vellalas). Sometimes, this lead to extreme positions by both sides that cannot be supported with reasonable evidence.
The present city of Madurai in its present site itself is quite old.
But a more ancient site of an earlier Madurai city is south - west to the
present city. The Pandyas had their main palace in that
site. In fact their throne - room was in that place. Incidentally, their Imperial throne was known as "KaLingaraayan". There are evidences that the river Vaigai, at one time was flowing over the site of the present Miinaatchi temple. At another time, it was running south of the present Madurai. That can be considered as during the historic times also. There is another name for Vagai. It was also known as Kirudhamaalai river. At present, you can see a big sewer- or shall we say a small canal - running around the whole of Madurai. It communicates with Vagai at both ends. It is labelled in old maps of Madurai city as "Kirudhamaal" river. The map, prepared for use by the East India Company, shows it as such. I think most Madurians won't know its very existence:-) The Miinaatchi temple seems to have shifted three times, all within the present Madurai City itself.
Tamil belongs to the Dravidian family, which contains about two dozen
living languages mostly spoken in southern and eastern India. All
of these are descended from a single ancestor, Proto-Dravidian (PD).
PD was not written down, since its speakers were illiterate, but
specialists estimate that it was probably spoken around 4000 BC. Some time after that date, PD began to break up into several distinct languages, which formed the ancestors of the four main groups of Dravidian recognized today. South Dravidian, to which Tamil belongs, is thought to have been the last group to split off, perhaps around 1500 BC. Tamil, therefore, probably separated from its closest relatives around 1000-500 BC.
The first written text in Tamil is an inscription usually dated to 254 BC. This makes Tamil the first Dravidian language to be recorded, and one of the first languages of India to be written.
The striking thing about Tamil is that it is the only Indian language which has a continuous and uninterrupted written tradition dating back as far as 2000 years. In the north, the written tradition of the Indo-Aryan languages is discontinuous: the Indo-Aryan languages that were written down 2000 years or more ago are not the direct ancestors of the ones that have been written more recently.