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Facilitated Variation: How Evolution Learns from Past Environments To Generalize to New Environments

Summary: Facilitated Variation: How Evolution Learns from Past
Environments To Generalize to New Environments
Merav Parter.
, Nadav Kashtan.
, Uri Alon*
Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
One of the striking features of evolution is the appearance of novel structures in organisms. Recently, Kirschner and Gerhart
have integrated discoveries in evolution, genetics, and developmental biology to form a theory of facilitated variation (FV).
The key observation is that organisms are designed such that random genetic changes are channeled in phenotypic
directions that are potentially useful. An open question is how FV spontaneously emerges during evolution. Here, we
address this by means of computer simulations of two well-studied model systems, logic circuits and RNA secondary
structure. We find that evolution of FV is enhanced in environments that change from time to time in a systematic way: the
varying environments are made of the same set of subgoals but in different combinations. We find that organisms that
evolve under such varying goals not only remember their history but also generalize to future environments, exhibiting
high adaptability to novel goals. Rapid adaptation is seen to goals composed of the same subgoals in novel combinations,
and to goals where one of the subgoals was never seen in the history of the organism. The mechanisms for such enhanced
generation of novelty (generalization) are analyzed, as is the way that organisms store information in their genomes about
their past environments. Elements of facilitated variation theory, such as weak regulatory linkage, modularity, and reduced
pleiotropy of mutations, evolve spontaneously under these conditions. Thus, environments that change in a systematic,


Source: Alon, Uri - Departments of Molecular Cell Biology & Physics of Complex Systems, Weizmann Institute of Science


Collections: Biology and Medicine