Bedau
has developed a
general set of evolutionary statistics that quantify the adaptive
component of evolutionary processes. On the basis of these measures,
he has proposed a set of 4 classes of evolutionary system. All
artificial life sytems so far looked at fall into the first 3
classes, whereas the biosphere, and possibly the human economy
belongs to the 4th class. The challenge to the artificial life
community is to identify exactly what is difference between these
natural evolutionary systems, and existing artificial life systems.
At ALife VII, I presented a study using an artificial evolutionary
ecology called
Eco Lab.
Bedau's statistics captured
the qualitative behaviour of the model.
Eco Lab exhibited
behaviour from the first 3 classes, but not class 4, which is
characterised by unbounded growth in diversity.
Eco Lab exhibits a
critical surface given by an inverse relationship between
connectivity and diversity, above which the model cannot tarry long.
Thus in order to get unbounded diversity increase, there needs to be
a corresponding connectivity reducing (or food web
pruning) process. This paper reexamines this question in light of
two possible processes that reduce ecosystem
connectivity: a tendency for specialisation
and increase in biogeographic
zones through
continental drift.