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occurs during sexual reproduction. Consequently, many erroneously assume
that homologous recombination creates more diversity despite several facts
against this hypothesis (Margulis and Sagan 1997). The comparison of GEP
operators, especially recombination, suggests that a more conservative
recombinational mechanism such as homologous recombination would only
be useful for maintaining the status quo in periods of stasis. Interestingly,
this hypothesis is further supported by the kind of evolutionary dynamics
found in populations undergoing recombination alone (see the sudy on Re-
combination in the next section).
12.1.2 Evolutionary Dynamics of Different Types of Populations
The analysis of the evolutionary dynamics of some of the populations shown
in Figure 12.1 can be helpful to gain some insights into the adaptive strength
of different evolutionary systems. The most interesting are those with the
highest performances and those are, obviously, the ones we are going to
analyze first, comparing them with other, less efficient systems.
Mutation
Based on the analysis of Figure 12.1, the study of key populations undergoing
mutation can be used as a reference against which other populations undergoing
different genetic modifications could be compared. Populations on the
ascending side of the mutation plot are healthily evolving under small mutation
rates and, therefore, are generally called healthy populations. Populations on
the descending side are evolving under excessive mutation and are generally
called unhealthy . Obviously, populations at the peak have an ideal mutation
rate. Figure 12.2 shows how populations behave in terms of average fitness
and how the plot for average fitness relates to the plot for best fitness as
populations move along the mutation curve of Figure 12.1.
In the first evolutionary dynamics, p m = 0.001 and Ps = 16% (plot a ), the
plot for average fitness closely accompanies the plot for best fitness and only
a small oscillation is observed in average fitness. These populations are called
moderately innovative as they evolve very sluggishly and only a little bit of
genetic diversity is introduced in the population.
In the second dynamics, p m = 0.0045 and Ps = 48% (plot b ), it can be
observed that, although closely accompanying the plot for best fitness, the
gap between both plots increases and the characteristic oscillatory pattern on
average fitness is already evident even for such small variation rates. As
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