Vratyas in Magadha also suggest the presence of diverse cultures in the
middle Ganga plain.
    The extension of settlements may have been due both to groups branching
off and migrating further away from the earliest settlements, as well as to
some increase in population. There would also have been the merging of
earlier settlements with new ones, which would have resulted in larger
settlement sizes. Early PGW sites are characterised by small settlements
fairly closely spaced.
Economy A comparative study of the early and late Vedic texts suggests a
gradual change from pastoralism to agriculture as the predominant economy,
although the former never totally declined in the western Ganga plain. The
economic pattern varied, however, from area to area. Thus, the region around
Mathura continued to be substantially pastoral for many centuries, whereas
the middle Ganga plain has limited evidence of pastoralism. The change in
the economy can be gathered from indirect sources: there are fewer
references to cattle in specific contexts and more references to grain in the
same contexts. Thus, in the major sacrificial rituals such as the rajasuya, the
offerings based on dairy produce are less frequent as compared to those
which are derived from agricultural products.
    Agriculture implies some control over land and forms of irrigation. In
north Bihar, the description of rice cultivation is that of wet rice. A single
crop of rice can be obtained by relying on the seasonal rainfall to provide the
necessary water. The marshes of the middle Ganga plain would have had to
be drained and this would have required labour. Wet rice cultivation is also,
in itself, labour intensive. Such activities would not only necessitate the
availability of labour, but also a social distance between those who laboured
and those who controlled the labour. This would mean a society where a few
were powerful and could order the larger numbers to work for them.
Society These changes had a bearing on other changes in society. The
origin of caste has generally been traced back to the Vedic sources and the
society to which they refer, since the earliest references to varnas come from
these texts. The more complex nature of society in the later Vedic texts is in
part, suggested by the frequency of references to the four varnas. These four
are not only mentioned, but their various functions are described and their