Evolutionary theories are essential for explaining what exists on our planet, biologically and culturally. Could they also be essential at a much larger scale, for explaining the features of our universe, including the fact that it contains intelligent life? There’s a line of thinking from theoretical physics that seriously considers this possibility, by suggesting that our universe could be the product of cosmological natural selection (CNS). It’s an approach that many will regard as truly far-fetched, but may seem slightly less so if you consider the rationale on which it is based. Theories of CNS depend on the assumption that our own universe is only one among innumerable others ─ that is, we live in a multiverse. The multiverse concept may itself seem far-fetched, but it’s a topic of serious debate among many of the world’s most accomplished physicists. Various kinds of multiverses have been hypothesized to exist, and academic heavyweights and/or science popularizers who have espoused these hypotheses include Sean Carroll, Brian Cox, David Deutsch, Brian Greene, Alan Guth, Stephen Hawking, Michio Kaku, Andrei Linde, Laura Mersini-Houghton, Leonard Susskind, Max Tegmark, and Neil deGrasse Tyson.The kind of multiverse proposed by CNS is one of self-replicating universes, analogous to reproducing organisms. Competition to replicate results in some kinds of universes being more represented than others, with the most-represented being those best able to replicate themselves faithfully, with their constituent physical laws intact. Thus universes evolve to be ‘selfish’—that is, as if they were interested in propagating their own kind—just as biological organisms act as if they were interested in spreading their own genes.1 By what mechanism could a universe self-replicate? According to the best-known CNS theory, Lee Smolin,2,3—in work that builds on an earlier idea suggested by one of the great physicists of the 20th century, John Wheeler4—proposes that black holes are the mechanism, and thus that selection favours universes that contain more black holes. (Our own observable universe, by the way, probably contains about 100 billion black holes). The idea that black holes give birth to baby universes has an unusually high degree of intuitive appeal for a cosmological theory (as such theories can often seem abstruse and bizarre). This is because a black hole does seem reasonably interpretable as the inverse, or ‘other side’, of a big bang: a black hole results in a ‘singularity’—an infinitely small concentration of space-time, matter, and energy—and a big bang emerges from a singularity, as an explosive expansion of space-time, matter, and energy. Smolin suggests that in such a process, a baby universe may ‘inherit’ physical parameters from its parent, thus enabling some degree of self-replication.Other theories have suggested that intelligent life could also be a mechanism by which universes replicate themselves – a concept known as ‘cosmological natural selection with intelligence’ (CNS-I). It’s an idea with striking implications for organisms like us, as it proposes that we could serve an identifiable function in a process of cosmic replication, but it’s less well-known than Smolin’s black hole theory. (For an interesting conversation between Robert Wright and Lee Smolin about how CNS-I relates to Smolin’s theory, click here). Various takes on CNS-I have been proposed, by mathematician Louis Crane,5 cosmologist Edward Harrison,6 and most prolifically, amateur cosmologist James Gardner.7-13One way to summarize CNS-I is to quote Harrison, who in 1995 published the first peer-reviewed case for it: “Not inconceivably, the goal in the evolution of intelligence is the creation of universes that foster intelligence.”6 A shared assumption of all CNS-I theories is that sufficiently evolved intelligence could acquire the ability to create new cosmic environments for itself that, in order to be habitable, would need to replicate the physical laws of its native universe. Cosmologists expect that billions of years from now our own universe will cease being habitable (due to, for example, a ‘big freeze’ or ‘big crunch’), but by that point intelligent life could conceivably have become sophisticated enough to produce a new life-supporting universe. From this perspective, life is of crucial importance on a cosmic scale; essentially, it’s the universe’s reproductive system. That doesn’t mean that earthly life is the only kind that could enable this reproduction, and Gardner regards the hypothesis as implying that extra-terrestrial life is likely to exist.8 However, Ray Kurzweil14 has good arguments for why we’re probably alone in the universe, and he reiterates these in the foreword he wrote for Gardner’s second book.8 A notable feature of CSN-I is that it accounts for the seemingly improbable ‘bio-friendliness’ of our universe – the observation that many laws and parameters of the universe seem precisely adjusted to enable the evolution of life.15,16 If any one setting in this complex configuration were tweaked even slightly, life would be impossible; it’s as if the universe were ‘designed’, against the odds, for the function of enabling life to emerge. Now on the one hand, to observe some minimal degree of bio-friendliness in our own universe is unsurprising and indeed compulsory, since observations of a universe must be compatible with characteristics of the observer (the ‘anthropic principle’): of course our own universe is conducive to life, otherwise we wouldn’t be here to observe it. But on the other hand it’s not at all clear that such bio-friendliness would be compulsory in all possible universes, which raises the ‘fine tuning’ problem that has intrigued and challenged many physicists.15,16 CNS-I could provide a solution to this long-standing problem, because one basic lesson of evolutionary theory is that natural selection processes are brilliant at producing improbable, complex, functional design. Natural selection is the only known force that can generate complex functionality (that is, adaptation) at the biological level, and it’s interesting to consider that it could also do so at a cosmological level, and that life itself—along with the physical conditions that permit life to exist—could potentially be regarded as a higher-order adaptation.Although the concept of CNS-I will seem outlandish to many, this really shouldn’t disqualify it from further consideration, as physics since Einstein has already established firmly that our cosmic habitat is, in fact, fundamentally strange. However it’s clearly very speculative, and I’m not arguing that it’s correct – no one knows if it’s correct, because scientists don’t currently possess the methods that would enable them to test it in anything close to a conclusive manner. It’s a new and inchoate story with many missing pages, and it raises at least as many questions as it could potentially answer. But it does seem worth keeping in mind as a possible starting point for explaining why life exists in our universe, especially because it’s grounded in assumptions about evolutionary processes—for example, that selection among replicators can produce improbable functional complexity—that we already know to be true at the biological level. It simply proposes that similar processes may also operate at a cosmological level. And although CNS-I is speculative indeed, it’s not necessarily more speculative than the leading alternative scientific view: that life is an accidental and ultimately purposeless by-product of larger cosmic processes. References:1. Dawkins, R. (1976). The Selfish Gene. Oxford University Press.2. Smolin, L. (1992). Did the universe evolve? Classical and Quantum Gravity 9: 173-191.3. Smolin, L. (1997). The Life of the Cosmos. Oxford University Press.4. Wheeler J. A. (1974). Beyond the end of time. In M. Rees, R. Ruffini and J. A. Wheeler (Eds.), Black Holes, Gravitational Waves and Cosmology: An Introduction to Current Research. Gordon and Breach.5. Crane, L. (1994). Possible implications of the quantum theory of gravity: an introduction to the meduso-anthropic principle. arXiv:hep-th/9402104v1.6. Harrison, E. R. (1995). The natural selection of universes containing intelligent life. Quarterly Journal of the Royal Astronomical Society 36: 193-203.7. Gardner, J. N. (2003). Biocosm: The New Scientific Theory of Evolution: Intelligent Life is the Architect of the Universe. Inner Ocean Publishing.8. Gardner, J. N. (2007). The Intelligent Universe: AI, ET, and the Emerging Mind of the Cosmos. New Page Books.9. Gardner, J. N. (2000). The selfish biocosm. Complexity 5: 34-45.10. Gardner, J. N. (2001). Assessing the robustness of the emergence of intelligence: Testing the selfish biocosm hypothesis. Acta Astronautica 48: 951-955.11. Gardner, J. N. (2002). Assessing the computational potential of the eschaton – testing the selfish biocosm hypothesis. Journal of the British Interplanetary Society 55: 285-288.12. Gardner, J. N. (2004). The physical constants as biosignature: An anthropic retrodiction of the selfish biocosm hypothesis. International Journal of Astrobiology 3: 229-236.13. Gardner, J. N. (2005). Coevolution of the cosmic past and future: The selfish biocosm as a closed timelike curve: A recipe for cosmic ontogeny and a blueprint for cosmic reproduction. Complexity 10: 14-21.14. Kurzweil, R. (2005). The Singularity is Near: When Humans Transcend Biology. Penguin.15. Rees, M. (2001). Our Cosmic Habitat. Princeton University Press. 16. Davies, P. (2006). The Goldilocks Enigma: Why is the Universe Just Right for Life? Penguin.