Smolin's Cosmological Natural Selection
Universes evolve by natural selection. Black holes are reproductive events, and our universe is descended from ancestors that were good at making black holes.
Placeholder for a 3D visualisation of Cosmological Selection. The interactive scene will land in Phase 3. Black holes are not endpoints but birthplaces. Each black hole spawns a new universe with slightly different physical constants. Over many generations, universes that produce more black holes become statistically dominant, which means our universe should have physical constants that are nearly optimal for black hole formation.
In one sentence
Smolin proposed in 1992 that black holes give birth to new universes with mutated physical constants, producing a Darwinian process where our universe is fine-tuned not for life but for black hole production.
The claim
Lee Smolin's idea takes the multiverse seriously but introduces a selection mechanism. He proposes that every black hole that forms in a universe produces a new universe inside it, with slightly different physical constants (the strengths of the four forces, the masses of particles, the cosmological constant). The child universe expands away from the singularity and evolves on its own.
If physical constants are inherited with small random variations, then a Darwinian process emerges. Universes that produce more black holes have more offspring. Over many generations, the population of universes becomes dominated by configurations that maximize black hole production. We are inside one of these dominant lineages.
Crucially, this is a falsifiable theory. If our universe's physical constants were perturbed slightly, the rate of black hole formation would either increase or decrease. Smolin argues that our universe sits at a near-optimal point: most small perturbations would reduce black hole production. This is the 'fine-tuning for black holes' prediction, and it's been the subject of ongoing debate.
Smolin's proposal is unusual among multiverse theories because it offers a non-anthropic explanation for fine-tuning. We're not here because we're observers; we're here because our universe is good at making the kind of objects (black holes) that propagate themselves.
The family stance
A parent universe with slightly different physical constants existed before ours. Our universe was born inside a black hole that formed in that parent universe. The same process is happening inside our black holes right now, spawning further universes with their own variations.
Predictions
- Our universe is near-optimal for black hole formation
- Small changes to any physical constant should reduce the number of black holes formed
- The mass distribution of stars in our universe is biased toward producing more black holes than a random distribution would
- Some specific predictions about neutron star masses and other observable quantities
Evidence
- The theory makes falsifiable predictions, unlike most multiverse proposals
- Some of the predicted optimizations of physical constants appear consistent with observations
- Provides a non-anthropic explanation for the apparent fine-tuning of physical constants
- Croon & Pinckney (2024) extend CNS with a concrete dark-matter-seeded reproduction channel via helium white dwarf collapse into ~0.1 solar mass black holes, the first major extension of CNS in over a decade.
Counterpoints
- The "inheritance" mechanism (child universe inherits parent constants with mutation) is speculative and lacks derivation from fundamental physics
- Different choices of "selection criterion" give different answers; black hole production is one possible criterion among many
- Some specific predictions (e.g. about neutron star masses) have been contested by observation
- Critics argue the theory is unfalsifiable in practice because we can't observe other universes
Variants in this family
▸Go deeperTechnical detail with proper terminology
Smolin developed the proposal in his 1997 book 'The Life of the Cosmos' and in several technical papers. The key mechanism is that singularities inside black holes give rise to new expanding regions of spacetime (an idea going back to Pathria-Good and to John Wheeler's earlier speculation), and that quantum gravitational effects at the singularity could produce small random perturbations to physical constants.
The fine-tuning argument runs roughly as follows: the masses of fundamental particles and the strengths of forces determine which atomic nuclei are stable, which stars can form, and what their final masses are. Black hole formation requires sufficiently massive stars and sufficiently low metallicity in their progenitor gas clouds. Smolin argues that the observed values of physical constants are near a local maximum for black hole production rate.
Critics including Lawrence Krauss and Vilenkin have argued that the theory requires unobserved mechanisms (the inheritance process) and that its predictions about neutron star masses do not match observation. The debate continues; Smolin has updated the theory in response to specific objections.
Croon & Pinckney (2024) also show that CNS with this mechanism addresses the Boltzmann-brain problem on 10^14-year timescales, a long-standing objection to selection-based cosmologies.
References
- EstablishedSmolin, L. (1992). 'Did the universe evolve?' Class. Quantum Grav. 9, 173
- EstablishedSmolin, L. (1997). 'The Life of the Cosmos.' Oxford University Press
- EstablishedSmolin, L. (2006). 'The status of cosmological natural selection.' arXiv:hep-th/0612185
- Needs verificationCroon & Pinckney (2024) Cosmology of self-replicating universes in black holes formed by dark matter-seeded stellar collapse7 citations
Last reviewed May 14, 2026
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