Modeling Sustained Evolution in RePast


Laszlo Gulyas 
Computer and Automation Research Institute,
Hungarian Academy of Sciences
Budapest, Hungary
address@hidden

and

George Kampis
History and Philosophy of Sciences,
Eötvös University, Budapest
address@hidden


Abstract


Can we produce an existence-proof model, akin to von Neumann's model of 
self-reproduction, that exhibits open-ended evolution, with increasing 
diversity and complexity? This was the first challenge for agent-based
modeling on John Holland's list addressing the audience of SwarmFest in 2003. 
Evolutionary algorithms, as known today, converge to  an externally defined 
optimum and settle at a moderate level of diversity.

In this presentation we deal with the problem of open-ended evolution of new 
species, and prove that agent-based modeling techniques are capable of tackling 
this problem in ways inapproachable by traditional equation-based modeling. 
We present an agent-based simulation, implemented in RePast, that is based on 
the idea of 'fat' phenotypes which generate a changing interaction space. Such 
changes can, in turn, define new selection forces. In our sexual selection-based 
model, species are defined as reproductively isolated and functionally different 
sub-populations. New species occur when genetic mutations produce individuals with 
a new phenotype that lets them disregard existing mating preferences and thus 
redefines previously relevant interactions.