#944 Biological Evolution in an Infinite Multiverse

Dr. craig’s response

Your question, Michael, surfaces in intriguing debates over the origin of life (or abiogenesis). That term signifies the origin of biological life from non-life. With respect to explaining abiogenesis naturalistically, there are two broad camps within the origin of life community which we may call Necessitism and Contingentism. Necessitists hold that the origin of life is causally determined by the laws of physics and chemistry and therefore happens necessarily. Contingentists hold that the origin of life is due to the interplay of many independent causal factors and is therefore a highly improbable event.

It's fascinating that the rejection of theistic models of abiogenesis has led some naturalistic origin of life researchers, both necessitists and contingentists, to turn to outer space in order to support their account of life on Earth. Astrobiology is a fascinating new discipline spurred by the discovery during the 1990s of exo-planets, that is, planets outside our solar system. As it turns out, both necessitists and contingentists have a vested interest in the success of astrobiology’s search for life abroad.

Necessitists reason that if life is determined by nature’s laws apart from any very special conditions, then it ought to arise easily and widely throughout the universe. They are therefore motivated to find traces of life elsewhere in our solar system, for example, in meteorites or on other planets and moons. Unfortunately for the necessitist, no extra-terrestrial traces of life have yet been detected. 

For the contingentist who is a naturalist the enormous improbability of the origin of life on his own account prompts him to turn to outer space in an effort to make the odds of life’s arising naturally on Earth more tractable. For example, Edward Steele, along with 32 colleagues, argues vigorously that “the most plausible valid option for the origin of terrestrial life” is that life originated abiogenically somewhere in our cosmos and was “seeded here on Earth by life-bearing comets as soon as conditions on Earth allowed it to flourish.”[1] On the basis of evidence for terrestrial life before 4.1Gya, they maintain that the window of time available for life’s originating in some primordial soup “has been effectively closed.”[2] They conclude, “The transformation of an ensemble of appropriately chosen biological monomers (e.g. amino acids, nucleotides) into a primitive living cell capable of further evolution appears to require overcoming an information hurdle of superastronomical proportions, an event that could not have happened within the time frame of the Earth except, we believe, as a miracle.”[3] Claiming that life came to Earth from extra-terrestrial sources does not, of course, explain the origin of life, but, by multiplying the sites where life might originate by chance, it increases the odds of its doing so.

Indeed, given the inconceivable improbability of the origin of life anywhere in the cosmos by purely natural causes, some contingentists have gone so far as to adopt multiverse scenarios in order to explain the origin of life on Earth. For example, Eugene Koonin, claiming that the origin of a coupled system of replication and translation involving RNA or DNA is arguably “the hardest problem in all of biology,” contends that “the emergence of a coupled replication-translation system is unlikely to the extent of being, effectively, impossible.”[4] In order to solve this problem Koonin adopts the multiverse hypothesis. In an infinite multiverse, anything which can happen physically does happen; indeed, it happens infinitely many times over. Thus, he says, “spontaneous emergence of complex systems that would have to be considered virtually impossible in a finite universe becomes not only possible but inevitable.”

Now Koonin realizes that “A corollary of this hypothesis is that an RNA world, as a diverse population of replicating RNA molecules, might have never existed.”[5] For given the multiverse hypothesis, the RNA world turns out to be dispensable. One need not set the table in advance in order for the first living cell to arise, regardless of how improbable that might be! 

But this realization leads to an almost nightmarish scenario: “A crucial aspect of the framework developed here is brought about by a disturbing (almost nightmarish) but inevitable question: in the infinitely redundant world of [the multiverse], why is biological evolution, and in particular, Darwinian selection relevant at all? Is it not possible for any, even the highest degree of complexity to emerge by chance?”[6] Given the multiverse, biological evolution is just as dispensable as the RNA World. Fully “evolved” organisms just came into being by chance. No objection to such a scenario can be raised on the basis of its improbability, for in an infinite multiverse anything that can happen will happen and does happen an infinite number of times.

Koonin’s reply to his above question is faltering: “The answer is ‘yes’ but the question misses the point. Under the [multiverse] model, emergence of an infinite number of complex biotas by chance is inevitable but these would be vastly less common than those that evolved by the scenario that includes the switch from chance/anthropic selection to biological evolution.”[7] This assertion is false, for in an infinite multiverse the number of each kind of universe is identical: infinite. In the absence of some special measure of probability over worlds, we have no way of knowing that we live in a world in which organisms have evolved, any more than we can know that we are not Boltzmann Brains, isolated brains with illusory observations of a surrounding universe. Koonin’s appeal to the multiverse is thus self-defeating and would defeat evolutionary biology.

Need I add that these proponents of life from outer space are not scientific cranks but sober scientists driven by the daunting odds against the special conditions for life required by contingentism to appeal to the resources of outer space for relief? These problems for contingentism arise, however, only from its conjunction with naturalism, for on a theistic worldview God decrees which universe (or universes) exist and by his providential control directs it towards its ends.