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Evolutionary transitions and reversions in individuality.
Martijn A Schenkel1,2,3,4, J Arvid Ågren5,6, Manus M Patten1
1Department of Biology, Georgetown University, 37th and O St. NW, Washington DC, 20057, United States.
Journal of Evolutionary Biology
|January 28, 2026
Summary
Evolutionary transitions in individuality create individuals recognized across all concepts, preventing biologists from discussing specific individuality types and overlooking potential reversions. Reversions can be paradigmatic or agential, impacting the evolution of biological individuality.
Area of Science:
- Evolutionary Biology
- Philosophy of Biology
- Theoretical Biology
Background:
- Biological individuality manifests in diverse forms, including unicellular, multicellular, and colonial organisms.
- Evolutionary transitions in individuality involve the integration of lower-level entities into higher-level individuals.
- The precise nature of what
Purpose of the Study:
- To argue that evolutionary transitions in individuality consistently produce
Main Methods:
- Conceptual analysis of biological individuality.
- Identification and differentiation of two types of reversions: paradigmatic and agential.
- Examination of the role of internal conflict in agential reversions.
Main Results:
- Evolutionary transitions in individuality yield "paradigmatic" individuals, identifiable under any conceptual framework.
- This universality leads to ambiguity in evolutionary biology regarding specific individuality concepts.
- Two distinct forms of reversion are identified: paradigmatic (complete undoing of transition) and agential (shift in selection level).
Conclusions:
- Reversions, both paradigmatic and agential, represent crucial phenomena in the evolution of individuality.
- Agential reversions, driven by internal conflict, offer a novel perspective on individuality loss.
- Understanding reversions enhances the accuracy and complexity of theories on biological individuality and its evolutionary trajectory.
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