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The Croonian Lecture, 1991. Genostasis and the limits to evolution
1Department of Environmental and Evolutionary Biology, University of Liverpool, U.K.
Summary
Evolutionary change is often limited by a lack of beneficial genetic variation, a state termed genostasis. When suitable genetic variation is present, evolution can occur rapidly, highlighting the critical role of variation supply.
Area of Science:
- Evolutionary biology
- Genetics
Background:
- Darwinian evolution relies on genetic variation and natural selection.
- While genetic variation and natural selection exist, rapid evolution is not always observed.
- Many species exhibit remarkable stability, with evolutionary failure being common.
Purpose of the Study:
- To investigate the reasons behind the apparent lack of evolution in many species.
- To propose a new term, 'genostasis,' to describe the condition of limited evolutionary change.
- To explore the role of genetic variation supply in evolutionary processes.
Main Methods:
- The study reviews existing evidence on genetic variation and natural selection.
- It analyzes patterns of evolutionary stasis and rapid change in different species.
- Theoretical and practical considerations of variation supply are discussed.
Main Results:
- Despite high levels of protein polymorphism, the supply of variation significantly impacting fitness appears limited.
- Lack of appropriate genetic variability is proposed as the primary cause of evolutionary stasis (genostasis).
- Evolutionary change is rapid when suitable genetic variation becomes available.
Conclusions:
- The limited supply of beneficial genetic variation, or genostasis, is a key factor in evolutionary stasis.
- Understanding the mechanisms of new variation supply is crucial for explaining evolutionary patterns.
- Further research should focus on variation supply and instances of apparent evolutionary non-occurrence.