Аннотация
The problem of complex adaptations is studied in two
largely disconnected research traditions: evolutionary
biology and evolutionary computer science. This paper
summarizes the results from both areas and compares
their implications. In evolutionary computer science it
was found that the Darwinian process of mutation,
recombination and selection is not universally
effective in improving complex systems like computer
programs or chip designs. For adaptation to occur,
these systems must possess "evolvability", i.e. the
ability of random variations to sometimes produce
improvement. It was found that evolvability critically
depends on the way genetic variation maps onto
phenotypic variation, an issue known as the
representation problem. The genotype-phenotype map
determines the variability of characters, which is the
propensity to vary. Variability needs to be
distinguished from variation, which are the actually
realized differences between individuals. The
genotype-phenotype map is the common theme underlying
such varied biological phenomena as genetic
canalization, developmental constraints, biological
versatility, developmental dissociability,
morphological integration, and many more. For
evolutionary biology the representation problem has
important implications: how is it that extant species
acquired a genotype-phenotype map which allows
improvement by mutation and selection? Is the
genotype-phenotype map able to change in evolution?
What are the selective forces, if any, that shape the
genotype-phenotype map? We propose that the
genotype-phenotype map can evolve by two main routes:
epistatic mutations, or the creation of new genes. A
common result for organismic design is modularity. By
modularity we mean a genotype-phenotype map in which
there are few pleiotropic effects among characters
serving different functions, with pleiotropic effects
falling mainly among characters that are part of a
single functional complex. Such a design is expected to
improve evolvability by limiting the interference
between the adaptation of different functions. Several
population genetic models are reviewed that are
intended to explain the evolutionary origin of a
modular design. While our current knowledge is
insufficient to assess the plausibility of these
models, they form the beginning of a framework for
understanding the evolution of the genotype-phenotype
map.
Copyright 1996 Gunter Wagner and Lee Altenberg
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