Optimality arguments and modifier theory are reviewed as paradigms for
the study of the evolution of recombination. Optimality criteria (suc
h as maximization of mean fitness) may agree with results from models
developed in terms of the evolution of recombination at modifier loci.
Modifier models demonstrate, however, that equilibrium mean fitness c
an decrease during the evolution of recombination rates and is not alw
ays maximized. Therefore, optimality arguments do not successfully pre
dict the conditions under which increased or decreased recombination w
ill evolve. The results from modifier models indicate that decreased r
ecombination rates are usually favored when the population is initiall
y near a polymorphic equilibrium with linkage disequilibrium. When the
population is subject to directional selection or to deleterious muta
tions, increased recombination may be favored under certain conditions
, provided that there is negative epistasis among alleles.