that population densities were much higher than, for example, the Mature
  Harappan period. Also, the monarchical kingdoms of Magadha and Kosala
  and the northern republics emerged in the context of the later Iron Age in
  the Ganga plain.
    Since 1963, when D.D. Kosambi made the assertion that extensive forest
clearance and agrarian settlement would not have been possible in the Ganga
plains without the use of iron, archaeologists have been exploring the
connection between the introduction of iron technology, settlement patterns,
and political development in northern India.
Northwest Frontier and Kashmir
This region falls into at least three major areas: the stretch between Peshawar
and Taxila comprising the Peshawar valley and the Potwar plateau; the area
between Swat and Chitral; and finally, the valley of Kashmir.
    The Neolithic levels of Saraikhola in the Potwar plateau gave way to a
Kot Diji related horizon, and in some way this region as a whole was within
the trading network of the contemporary Indus plains.
    In the Swat-Chitral region the large number of sites that have been
excavated show the use of different metals, stone and other objects among
which are shell, coral and ivory which must have reached this region from the
Indus plains. The rock shelter site of Ghaligai, which perhaps goes back to
3000 BC, provides the baseline in Swat-Chitral.
    The ‘proto-historic graveyards’ of the region are dated between the
second quarter of the second millennium BC and the late centuries BC. The
evidence of such graveyards and associated settlements has been categorised
as the ‘Gandhara Grave Culture’. These Copper Age graves are marked by
intlexed burials and urn burials