208 Scarcity and Surfeit
The onset of the Nuer expansion corresponded with the closure of this out-
let and a period of higher than usual humidity.20 Wetter conditions in the Nile
Basin are magnified in the flood plain, and this together with increasing pop-
ulation densities ostensibly combined to trigger the expansion - the Nuer's
specialised adaptation to the swampy lower areas of the flood plain being the
other critical enabling factor.
While both groups occupy parts of the central clay plain, the Nuer expan-
sion filled the lowest part of a basin bounded to the south by the Ironstone
Plateau and to the north by the Nuba Hills. Nuerland appears to have been a
mosquito-laden swamp, poor for cattle, which had not been long occupied
prior to the nineteenth century. Dinka areas are less infested by the mosqui-
toes whose sheer numbers force the Nuer and their cattle into smoke-filled
byres at night. The Dinka occupied the higher ground to the north, south and
west of the depression, and prospered in respect to relative size of the two
p0pulations.2~
Ecological Factors Facilitating the Nuer Expansion
The environmental differences demarcating the Nuer and Dinka lands engen-
dered significant behavioural and livelihood differences. In the wet season, for
example, the Dinka characteristically observe a second phase of transhumance.
This is not possible for the Nuer. During the same period they are forced back
by the wider flooding of their country into the isolation of their separate villages,
which provide the only dry stands for the herdszz The distinct ecological habi-
tat of the Dinka, together with a closer relation between kinship and territorial-
ity, allowed the Dinka to stay close to their home camps throughout the year.
Nuer social structure features segmentary lineages, a common feature of
nomadic or transhumant groups that need to mobilise political support
among kinship units scattered across large areas on a periodic but unpre-
dictable basis. Clan organisation characterises the more sedentary Dh1ka.2~
These two kinship-based systems represent the traditional distributive agents
for the resources of the flood plain environment. Though cattle and grain are
equally necessary for survival, cattle served as the traditional systems' capi-
tal - and bride wealth provided the primary mechanism for redistributing
wealth across kin-linked households. The wider distributive requirements of
the Nuer lineage system required more cattle than the Dinka.
Kelly's24 argument that this factor - bride price-fuelled Nuer expansion -
is based on the observation that the ideal Nuer bride wealth requirements are
almost twice the number of cattle the Dinka ideally require. The actual Nuer
bride wealth payments recorded by ~vans-~ritchard~~ in the 1930s were
between 20 and 30, whereas 30 or 40 years earlier they had been 40 and often
even more. The acceptable number of cattle for Nuer bride wealth payments
varied to a degree in relation to herd sizes at the time, which were in turn
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