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1984;17(1):51-5.  Coevolution of functionally constrained
characters: prerequisites for adaptive versatility.   One of the
major problems of organismic evolution theory is to explain how
complex organisms were able to evolve by random mutations in
spite of the severe functional constraints that canalize their
route of change. The problem is discussed on the basis of a
quantitative genetic model. How the degree of genetic variation
influences the adaptation speed of functionally coupled but
genetically uncorrelated characters is examined. It was found,
that if more than three independent characters contribute to the
variation of a functionally constrained system, optimal degrees
of genetic variation exist. Higher degrees of variation lead to
decreasing adaptation rates. Conversely, functional constraints
do not limit the degree of adaptely reasonable genetic
variability as long as the number of independent characters is
not higher than three. The con