In his Book Review of The Goldilocks Enigma (“Life in the universal porridge” Nature 444, 423–424; 2006), Jim Al-Khalili discusses Paul Davies' answers to the question “Why is the Universe just right for life?”.
The question relies upon the widely held assumption that life, in particular human life, is a unique form of matter requiring a special explanation for its existence.
As a biologist, I agree that life is a fascinating phenomenon, and humans may well be among the most complex entities in the Universe.
However, all past and present life-forms on Earth have been the products of one particular evolutionary process, which was driven by natural selection and which operates on the basis of specific genetic mutations and selective environments. If these mutations and environments had been different, the products of this evolutionary process would also have differed. Indeed, the organisms we know of, including our own species, might never have evolved at all.
Thus, our existence does not require a special category of explanation, beyond natural selection. To think so can be seen as a form of chauvinism — seductive but misguided — that elevates the specific aggregates of matter on this planet, and their historically conditioned features, to an inappropriately lofty status.
This argument also applies to SETI, the search for extraterrestrial intelligence, which is based on the same tempting assumption. Life, consciousness and intelligence, as we know them, are highly unlikely to be found elsewhere in the Universe, nor are they likely to be inevitable consequences of any sufficiently 'advanced' darwinian system. Rather, they are specific outcomes of one particular process of evolution, occurring on one of the billions of planets in this Universe. (If the Multiverse exists, there could be other universes almost identical to ours, and therefore there could be other life-forms like us, but presumably we would not be able to communicate with them.)
These conclusions will be disappointing to many — as they are, sometimes, to me. But, as Richard Dawkins commented about people who have been disturbed by his book The Selfish Gene, in his Darwin@LSE public lecture in London this year, “If something is true, no amount of wishful thinking can undo it”.
Rather than leaving these matters, as Davies suggests, to “philosophers and priests”, or to physicists, perhaps we should listen to the biologists as well. Then some of these questions might be considered less troubling, and less important, than they currently seem to be.
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Wigley, P. Life: perhaps we should take the porridge theory with a pinch of salt. Nature 444, 1002 (2006). https://doi.org/10.1038/4441002a