Geoscience Reference
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gatherers). The author uses the Monte Carlo method to manage the two processes
involved at the agent level of the model:
- the demographic change: the agents have a certain probability of dying (natural
death or as a result of a conflict) and giving birth (by division if the agents are
groups) at each iteration. Death may also be caused by way of congestion (if too
many agents are located on the same cell);
- the migration: agents move about in space by following a random walk (eight
possible directions).
The model has been used to explore the patterns of colonization of an empty
space (Figure 4.7):
- if the growth rate is strong and migration rate is low, there is a front wave that
moves slowly in a progressive manner. The author refers to the diffusion of the
farmers during the Neolithic to illustrate this case, referring to the case of Indo-
Europeans and Bantus, for example, and also that of the North-American
colonization by the Europeans;
- if the growth rate is low and the migration rate is strong, there is no front. The
whole space is fairly rapidly invested, but in a diffused manner and with an overall
low density. The colonization of Australia during the Pleistocene is one example of
such a case [YOU 02].
Figure 4.7.
Simulation of the colonization front according to two sets
of parameters (source: [YOU 02])
