Success

“Success” is not a single biological (or other) variable. It depends on which entity is in focus, over what period, under what conditions, and according to which evaluative frame. Which entity's success counts is itself a prior value judgement, not a neutral starting point. The same event can register as success for one entity and failure for another: antibiotic treatment succeeds for the patient while eliminating the bacterial population; a plantation succeeds as a timber system while failing as habitat for most native species.

Evolutionary theory distinguishes selection and persistence at the levels of genes, organisms, groups, species and clades; ecology examines populations, communities and ecosystems; Earth-system science and astrobiology examine the biosphere and planetary habitability.1

A criterion appropriate to an individual organism may be incoherent or misleading when applied to an ecosystem, civilisation or planet.

A working definition:

The demonstrated capacity of a biological entity or system to persist, generate viable successors and enabling conditions, sustain or reconstruct essential functions, withstand environmental variation and avoid destroying the conditions required for its own continuation.

This is multidimensional and diachronic: it measures performance through time rather than temporary dominance.

Persistence

Cf.

Persistence asks whether an organism, population, lineage, process or system continues through time.

At the organismal level, survival generally matters because it contributes to reproduction.
At lineage and ecosystem levels, persistence may carry explanatory weight in its own right.
Philosophers of biology have proposed “differential persistence” as a broader complement to reproductive fitness, particularly for lineages, symbiotic associations and ecological systems that do not reproduce as clearly bounded organisms do.2
Microbial lineages, ecological interactions and nutrient cycles may persist through enormous environmental changes without any single organism or species remaining unchanged.

BUT persistence provides an insufficient criterion alone:

A system may persist through inertia, luck or destructive exploitation.
A population may persist while many of its members suffer; persistence at one level can coexist with harm at another.
Persistence must sit alongside generativity, resilience and viability.

Generativity

Cf.

Generativity means the capacity to produce descendants, diversity, ecological opportunities or environmental conditions that enable further life.

Three forms:

Reproductive generativity: production of descendants.
Evolutionary generativity: production of diversity, novelty and adaptive possibilities.3
Ecological generativity: production or renewal of conditions that support continuing life.4

A clade can generate ecological novelty, occupy new adaptive zones and create conditions for other organisms to diversify, beyond producing more copies of itself.
Earth-system generativity refers to the cumulative consequences of metabolism, photosynthesis, weathering, decomposition, symbiosis and niche construction.
Successful living systems participate in processes that renew or recirculate the conditions of production.

Tension: industrial societies perform strongly under forms 1 and 2, but form 3 remains contested. Technological novelty has expanded while many ecological conditions on which it depends degrade.

Functional Continuity

Cf.

Species composition can change while ecological processes continue. Photosynthesis, decomposition, nitrogen fixation, pollination, predation and nutrient recycling need not remain tied to one permanent set of species. Patterns of interaction may endure even as organisms turn over.5

Biospheric success consists partly of sustaining and reconstructing processes that permit life to continue despite taxonomic replacement and extinction.
Sustaining several functions simultaneously generally requires more biodiversity than maximising any single function.6

BUT functional substitutability is incomplete and contested:

One species may replace another in one process but not across its full ecological role.
From a more-than-human perspective, individual organisms are not interchangeable components; their particular evolutionary histories, relational lives and Umwelt-constituted experiences matter (cf. Biosemiotics).
Functional continuity arguments can be misused to justify extinctions on the grounds that something else will fill the niche.

Resilience

Cf.

Resilience concerns the capacity that helps produce persistence. The ability to remain near an equilibrium differs from the ability to absorb disturbance while retaining organisation and processes.7 Stability is itself multidimensional: resistance, recovery speed, variability through time, persistence and capacity to reorganise.8

A stronger test than performance under stable conditions asks whether a system can:

resist disturbance
recover after disturbance
reorganise without losing essential functions
adapt to altered conditions
transform when the existing configuration becomes impossible

Tensions:

High resistance does not always accompany rapid recovery once disturbance exceeds resistance.
High productivity can reduce redundancy or increase dependence on narrow conditions.
Biodiversity may contribute to resilience through differentiated responses to variation (“insurance hypothesis”),9 but diversity may appear inefficient under short-term optimisation.

Non-Self-Undermining Persistence

Cf.

A successful system should not systematically destroy the conditions required for its own continuation.

Natural selection does not guarantee foresight, sustainability or planetary regulation. Organisms can exhaust resources, alter environments and contribute to their own extinction.
Population viability analysis distinguishes current abundance from long-term persistence: a large population can still be moving towards collapse.10
Social–ecological resilience distinguishes persistence from adaptability and transformability: a society may maintain institutions while eroding the ecological base that supports them.11
The planetary-boundaries framework identifies biophysical processes whose destabilisation increases risks to human development.12

“Non-self-undermining” is preferable to “self-sustaining”: no organism or society sustains itself independently. The criterion asks whether a system participates in renewing its enabling relationships or progressively eliminates them.

Industrial civilisation has achieved exceptional short-term expansion, resource capture and technological generativity, but its success remains unproven under the more demanding criterion of maintaining the ecological and Earth-system conditions required for its continuation.

Thrivability: "non-self-undermining" sets too low a bar. Sustainability aims only to maintain the current state; the environment needs active repair until it can thrive.13 Thriving differs from success as used here: success tracks persistence and non-undermining conditions; thriving adds active vitality and the positive restoration of conditions for flourishing.

Criteria by Level of Organisation

Genes and Individual Organisms: Reproductive Fitness

Cf.

Evolution

In standard evolutionary theory, fitness concerns differential contribution to future generations.14 Under this frame, humans appear highly successful.

Limits:

Fitness is relative, local and environment-dependent.
It does not measure welfare, ecological benefit, complexity or long-term sustainability.
Individual fitness cannot be summed to calculate the success of a civilisation or biosphere.

Organisms: Umwelt and Lived Experience

Cf.

Biological fitness is not the same as a life lived well. An organism’s Umwelt — its species-specific perceptual and action world — constitutes a frame of significance independent of reproductive output.

A highly fecund individual can live under poor conditions.
A parasite can achieve high reproductive fitness while causing harm to its hosts.
Success at the organismal level may require asking whether an organism can exercise its characteristic capacities in an adequate environment.

Populations: Demographic Viability

Population growth rate
Probability of persistence over a defined period
Population size and age structure
Genetic diversity
Capacity for migration or recolonisation
Ability to adapt to environmental change
"Evolvability": the ability to generate heritable variation permitting further adaptive evolution15

A currently abundant population with little variation or narrow environmental tolerance may be less successful over longer periods than a smaller but more adaptable one.

Species: Duration, Abundance, Distribution and Niche Breadth

Geological duration
Number of individuals and biomass
Geographic range
Range of occupied habitats; climatic or dietary niche breadth
Resistance to extinction

Geographic range often reduces extinction risk.16 BUT:

Contemporary geographic spread can result from simplifying environments or displacing other species.
Range measures ecological reach, not necessarily durable or desirable success.
Invasive species and domesticated organisms demonstrate that spread alone tells us little.

Clades: Richness, Diversification and Persistence

Cf.

Evolution

Net diversification (speciation exceeds extinction) is a common measure.17 Additional criteria:

Total lineage duration
Ecological and morphological disparity
Occupation of multiple niches
Resistance to mass extinction
Capacity to generate descendant clades18

Richness, dispersal and internal diversity can conflict: a species-poor clade may prove remarkably persistent, while a rapid radiation may generate many short-lived species.

Communities and Ecosystems: Functioning and Stability

Cf.

Without reproductive fitness in the ordinary sense, community and ecosystem success refers to:

Productivity
Nutrient retention and recycling
Trophic integrity and biodiversity
Multifunctionality
Resistance, recovery and capacity to reorganise
Continuity of ecological interactions19

Biosphere and Planet: Habitability

Duration of inhabited conditions
Spatial extent of habitable environments
Diversity of viable metabolisms
Continuity of biogeochemical cycling
Recovery from planetary disturbances
Persistence of conditions compatible with complex life20

Critical distinction: “The Earth remained habitable” says much less than “habitable for whom, where and how long?” Biospheric survival does not guarantee human survival, existing ecosystems or most current species.

Societies and Civilisations: Continuity, Adaptability and Justice

Cf.

Biological persistence alone provides an ethically inadequate measure of civilisational success. A civilisation could persist through coercion, inequality or the destruction of nonhuman lives.

Continuity without ecological overshoot
Material and institutional adaptability
Equitable distribution of risks and resources
Intergenerational viability
Preservation of options for future generations
Coexistence with other species

At this level, “success” is partly normative. Scientific evidence identifies conditions that support persistence, but cannot alone determine what a good society is.

Sentient Beings: Welfare and Flourishing

Cf.

When the object of evaluation is a being rather than a lineage or ecosystem, success may mean living well rather than reproducing extensively.

Bodily integrity
Freedom from suffering
Social relationships and communication
Agency and play
Opportunity to exercise species-characteristic capacities (Nussbaum’s capabilities approach)21

Tension with evolutionary success: a highly fecund animal population can experience intense suffering; a parasite can achieve high reproductive fitness by harming its hosts. Biological success does not equal moral value, and the reverse is also true.

Footnotes

Okasha, Samir. Evolution and the Levels of Selection. Oxford: Clarendon Press, 2006.˄
Bouchard, Frédéric. “Causal Processes, Fitness, and the Differential Persistence of Lineages.” Philosophy of Science 75, no. 5 (2008): 560–70. https://doi.org/10.1086/594507.˄
Faurby, Søren, and Alexandre Antonelli. “Evolutionary and Ecological Success Is Decoupled in Mammals.” Journal of Biogeography 45, no. 10 (2018): 2227–37. https://doi.org/10.1111/jbi.13411.˄
Boyle, Richard A., and Timothy M. Lenton. “The Evolution of Biogeochemical Recycling by Persistence-Based Selection.” Communications Earth & Environment 3, no. 1 (2022): 46. https://doi.org/10.1038/s43247-022-00371-3.˄
Doolittle, W. Ford, and S. Andrew Inkpen. “Processes and Patterns of Interaction as Units of Selection: An Introduction to ITSNTS Thinking.” Proceedings of the National Academy of Sciences 115, no. 16 (2018): 4006–14. https://doi.org/10.1073/pnas.1722232115.˄
Hector, Andy, and Robert Bagchi. “Biodiversity and Ecosystem Multifunctionality.” Nature 448, no. 7150 (2007): 188–90. https://doi.org/10.1038/nature05947.˄
Holling, C. S. “Resilience and Stability of Ecological Systems.” Annual Review of Ecology and Systematics 4 (1973): 1–23.˄
Donohue, Ian, Helmut Hillebrand, José M. Montoya, Owen L. Petchey, Stuart L. Pimm, Mike S. Fowler, Kevin Healy, et al. “Navigating the Complexity of Ecological Stability.” Ecology Letters 19, no. 9 (2016): 1172–85. https://doi.org/10.1111/ele.12648.˄
Yachi, Shigeo, and Michel Loreau. “Biodiversity and Ecosystem Productivity in a Fluctuating Environment: The Insurance Hypothesis.” Proceedings of the National Academy of Sciences 96, no. 4 (1999): 1463–68. https://doi.org/10.1073/pnas.96.4.1463.˄
Morris, William F., and Daniel F. Doak. Quantitative Conservation Biology: Theory and Practice of Population Viability Analysis. Sunderland, MA: Sinauer Associates, 2002.˄
Walker, Brian, Crawford S. Holling, Stephen Carpenter, and Ann Kinzig. “Resilience, Adaptability and Transformability in Social–Ecological Systems.” Ecology and Society 9, no. 2 (2004): 1–9. https://doi.org/10.5751/es-00650-090205.˄
Rockström, Johan, Will Steffen, Kevin Noone, Åsa Persson, F. Stuart Chapin Iii, Eric F. Lambin, Timothy M. Lenton, et al. “A Safe Operating Space for Humanity.” Nature 461, no. 24 (2009): 472–75. https://doi.org/10.1038/461472a.˄
Delaney, Tim, and Tim Madigan. Beyond Sustainability: A Thriving Environment. 2014. 2nd ed. Jefferson: McFarland, 2021.˄
Godfrey-Smith, Peter. Darwinian Populations and Natural Selection. New York: Oxford University Press, 2009.˄
Pigliucci, Massimo. “Is Evolvability Evolvable?” Nature Reviews Genetics 9, no. 1 (2008): 75–82. https://doi.org/10.1038/nrg2278.˄
Payne, Jonathan L., and Seth Finnegan. “The Effect of Geographic Range on Extinction Risk during Background and Mass Extinction.” Proceedings of the National Academy of Sciences 104, no. 25 (2007): 10506–11. https://doi.org/10.1073/pnas.0701257104.˄
Stanley, Steven M. “A Theory of Evolution above the Species Level.” Proceedings of the National Academy of Sciences 72, no. 2 (1975): 646–50. https://doi.org/10.1073/pnas.72.2.646.˄
Doolittle, W. Ford. “Making the Most of Clade Selection.” Philosophy of Science 84, no. 2 (2017): 275–95.˄
Bouchard, Frédéric. “Ecosystem Evolution Is about Variation and Persistence, Not Populations and Reproduction.” Biological Theory 9, no. 4 (2014): 382–91. https://doi.org/10.1007/s13752-014-0171-1.˄
Cockell, Charles S., Thomas Bush, Casey Bryce, Susana Direito, Martin Fox-Powell, John P. Harrison, Helmut Lammer, et al. “Habitability: A Review.” Astrobiology 16, no. 1 (2016): 89–117. https://doi.org/10.1089/ast.2015.1295.˄
Nussbaum, Martha Craven. Frontiers of Justice: Disability, Nationality, Species Membership. Cambridge, MA: The Belknap Press of Harvard University Press, 2007.˄