Population thinking is among the most discussed yet least understood concepts in philosophy of biology, largely because its central notion—biological uniqueness— remains theoretically underdeveloped. This project addresses the following question: What is the conceptual status of biological uniqueness, and how does a clarified account reshape current debates in biology, metaphysics, and environmental ethics?

By offering a positive account of uniqueness, this project will show its significance for current biological research, metaphysics of biology, and contemporary environmental ethics. Building on Nicholson’s recent reconstruction, I argue that uniqueness is best understood as informational complexity— the structured, relational configuration characteristic of living systems. The project examines how this notion illuminates debates on biological individuality and variability, and also explores its implications for environmental ethics. The main hypothesis driving my investigation is we should recognize the philosophical potency of Mayr’s original idea of “population thinking”, as a concept where the biological, metaphysical and ethical dimensions overlap in a fruitful way. Following this hypothesis, I will address population thinking from these three main perspectives.

Biologically, I will analyze the pervasiveness of biological uniqueness across different scales—from biomolecules to populations and ecosystems. Rather than being an exceptional phenomenon, uniqueness shapes biological phenomena from the genetic to the ecosystemic and evolutionary levels. This extreme variability is a major reason why, unlike in the physical sciences, predictions, generalizations, and theoretical modeling are comparatively difficult in biology. This will also highlight how population thinking informs recent efforts to incorporate individual-level differences in biological modeling. By offering a positive, biologically informed account of uniqueness as informational complexity, the project also connects to recent work on the role of information in biology.

Metaphysically, the focus on biological uniqueness helps reframe discussions on the ontology of biological individuality, and connects with process-based ontological frameworks, hence revaluing the importance of metaphysics for biology. While most contemporary interpretations of population thinking seek to limit the metaphysical scope that Mayr originally attributed to it, my approach follows Mayr’s original intuition, reframing Darwinian thought not merely as a theory of species change, but as a profound reorientation in our metaphysical conception of nature— one that directly conflicts with the longstanding Aristotelian substantialist and essentialist framework that continues to inform many ontological assumptions behind biological concepts.

Finally, the project extends into the ethical sphere. Building on the framework of biocultural ethics, I argue that the radical acknowledgment of uniqueness demands a deep rethinking of our normative relations to the natural world, demanding a pluralist and transdisciplinary perspective, connecting scientific practice with situated forms of knowledge. Biocultural ethics emphasizes the role of evolutionary and ecological science in recovering situated and increasingly threatened forms of non-scientific knowledge—crucial for responding to the rapid loss of habitats and cultures. Since there is no “single” correct way develop ethical and environmental skills, nor “universal” methodologies to be applied in environmental interventions, biocultural ethics promote specific strategies that reflect the unique qualities of each ecosystem and each community, and thereby fosters a strong dialogue between science and Indigenous forms of knowledge.

This synthesis of biological, philosophical, and ethical insights positions population thinking as a timely conceptual resource for addressing the accelerating loss of habitats and cultures in the present world.