The extreme southern part of India from the Tirupati hill (Vengadam) also known as Pullikunram in an Aham passage to Cape Comorin (Kanyakumari), bounded by sea on the east and the west, was known as Tamilgam, Tamilham, Tamilkam or Tamizhakam (the Tamil realm). This region comprises of the modern States of Kerala, Tamil Nadu and the Union Territory of Pondicherry.
The early historical period in this region, which followed the pre-historic period, witnessed the emergence, maturing and dissolution of a clearly identifiable social formation. It was more or less co-terminous with the beginning of the Iron Age in this part of the subcontinent. Iron appears to have arrived in South India without a preceding Copper/Bronze Age or a Chalcolithic Age.
Historians assign a variety of sources to this period: the megaliths and their grave goods; the hero- stones; the Tamil Brahmi cave labels; the early Tamil anthologies; the punch-marked coins; references in the Arthasastra and in Asokan edicts; occasional sherd of the NBPW; a scholium of Katyayana on Panini; Megasthenes; Greeco-Roman accounts; the archaeology and numismatics of Roman presence and so on the early historiography looked at this civilization as representing the “classical” epoch of South Indian history, which rubbed shoulders with the Roman Empire. However, recent historians do not entirely subscribe to this view.
It is now generally believed that the Cholas, Pandyas and Keralaputras mentioned in the Asokan inscriptions were probably in late megalithic phase of material culture which produced paddy and ragi this late megalithic phase came in contact with the northern material culture brought by traders, conquerors and Jain, Buddhist and some Brahmana missionaries.
This contact resulted in the introduction of wet paddy cultivation, founding of permanent villages and towns and ultimately the kingdoms of the Chola, the Chera and the Pandya. The trans-oceanic trade with the Roman Empire also contributed to the formation of these three early kingdoms.