There have been repeated attempts in the history of comparative biology to provide a mechanistic account of morphological homology. However, it is well-established that homologues can develop from diverse sets of developmental causes, appearing not to share any core causal architecture that underwrites character identity. We address this challenge with a new conceptual model of Character Identity Mechanisms (ChIMs). ChIMs are cohesive mechanisms with a recognizable causal profile that allows them to be traced through evolution as homologues despite having a diverse etiological organization. Our model hypothesizes that anatomical units at different levels of organization—cell types, tissues, and organs—have level-specific ChIMs with different conserved parts, activities, and organization. Relying on a methodology of conceptual engineering, we show how the ChIM concept advances our understanding of the developmental basis of morphological characters, while forging an important link between comparative and mechanistic biology.
Bibliographical noteFunding Information:
ACL and GPW gratefully acknowledge the financial support of the John Templeton Foundation (Grant Number 61329). The opinions expressed in this paper are those of the authors and not those of the JTF. JD thanks the Research Foundation?Flanders (FWO) for financial support (Grant Number 41277) and for funding a research stay at Yale University in Spring 2020, where most of this paper was written.
- Cell types
- Comparative biology
- Developmental mechanisms
- Levels of organization