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Developmental genetics and traditional homology
1Indiana Institute for Molecular and Cellular Biology, Indiana University, Bloomington 47405, USA.
Summary
Homology, defined by shared gene expression, is a flawed concept. Developmental genetics can aid homology identification but doesn't necessitate a new definition of evolutionary homology.
Area of Science:
- Evolutionary biology
- Developmental genetics
- Comparative morphology
Background:
- The concept of homology evolved from comparative morphology to evolutionary theory.
- Recent proposals redefine homology based on shared gene expression patterns.
Purpose of the Study:
- To critically evaluate the proposed redefinition of homology based on gene expression.
- To assert that a biological level must be specified for meaningful homology assignments.
Main Methods:
- Conceptual analysis of homology definitions.
- Comparison of classical and developmental genetic criteria for homology.
Main Results:
- The proposed definition conflates homology definition with identification criteria.
- Developmental genetic data are neither necessary nor sufficient for defining homology.
- Meaningful homology requires specifying a biological level (e.g., molecular, developmental, morphological).
Conclusions:
- Shared gene expression does not constitute a sufficient basis for a new definition of homology.
- Classical and evolutionary concepts of homology remain valid.
- Developmental genetic data should be integrated with, not replace, existing frameworks for understanding homology.