When we sit to write history of the Vedic Age India, generally it is understood that, the Rigveda is the sole authority to supply information to be used for reconstruction of history forgetting the fact that it is not so. When we talk about the Vedic India, we are taking about not only the era of final shaping of the Four Vedas but also of the period covered by the composition of the Brahamans, Arnayaks, Upnishadas and other auxiliary literature also which throws a flood of light on the Vedic Age culture and life of various tribes.
Moreover, tradition based literature contained in the oldest Pauranic and Epic literature also has to be used after sifting chaff from the floor with critical analysis. In this way, comparative study can only lead to right path of reconstruction of ancient history of India or any part of the world.
Then, one would have to look all around for availability of archaeological remains, if any, available to compare and contrast the data so collected and then only one could proceed to finally declare that one's hypotheses could be called conclusion. Also one has to remember that conclusions so arrived in social sciences and history are subject to revision on availability of newer data from time to time.