selection effects of surprise preferences can lead new song “species”
to emerge and differentiate from each other over time.This effect is
shown in figure 20.5.Thus,as choir size is increased,diversity across
the whole population can be replaced by diversity between speciated
subpopulations.Implications and Conclusions
Our simulations lend support for the role of coevolving songs and direc-
tional (surprise-based) preferences in creating and maintaining musical
diversity.Evolution is likely to stagnate unless females choose songs
based not just on evolved preferences but also on a desire to be surprised
by what they hear.Loosely speaking,when females are bored by the
same old song,males must strive to provide them with something new
to ensure their own mating success.As a consequence,a variety of male
songs evolves,both within a single generation and across successive
generations over time.With noncoevolving,nondirectional preferences,
progress is slower and diversity collapses.383 Simulating the Evolution of Musical Behavior
Figure 20.3
Diversity of songs in each generation G,from G =1 at top to G =1,000 at bottom.Each
point shows the number of pairs of songs that have a certain number of notes different
between them.Here,diversity is preserved in a coevolving surprise-preference sample-size-
two population.Fig.20.3