Wallace Arthur's «The Biological Universe» and the role of human-level intelligence in the future of life in the universe

This is not really a review of the new book The Biological Universe, by Wallace Arthur; just a few critical points. 

First, Arthur hardly mentions the Fermi conundrum, which, in its fully evolved form, is one of the principal pieces of evidence for the inference that intelligent life, and, probably, what he doesn't like to call "complex" life, are, respectively somewhere between very, very to extremely rare; and at least quite rare. Fermi isn't even circumstantial evidence for the the rarity of complex life per se, except insofar as the presumption is that if life elsewhere reaches the level of say the Cambrian era on Earth (highly complex, long-term stable biosphere with high degree of penetration of all habitats on the planet), it is probably something on the order of at least 1 to 3% likely to evolve to human level intelligence. And if you assume such intelligence is even 1% likely to survive to the level where it is a spacefaring and spacedwelling species, capable of spreading its particular architecture of life far and wide in at least one galaxy, then if you assume that life of this kind is relatively common (as Arthur does), the numbers still don't add up if intelligent life arising even on these life bearing worlds isn't also exceedingly rare. Note that the number of planets with microbial life at any given time is assumed by Arthur, plausibly, to be something like 10 million planets in a galaxy the size of Milky Way  (which is still something like 0.0001% of all planets in the galaxy). 

 

Bottom line, you have to acknowledge that the evidence best supports not a rare life or even extremely rare "complex" life but certainly a very rare human-level intelligence condition. Arthur doesn't really disagree with this but he doesn't address it well at all. The inferential evidence of rare intelligence as an implication that extremely robust and complex life biospheres may be more unlikely than he seems to believe is ignored. 

His main thesis is that the "rare Earth" view is wrong,* and he disputes the very concept of "complex" life, but ultimately his main evidence for this is the same old Earth-centric view of the probability of various "filters" in the evolution of life. Having said that, he did convince me that both eukaryotism (if that's a word)**, or some analogue of it, and photosynthesis are probably closer to inevitable than they are to being filters, in the sense of potential stumbling blocks to the evolution of more "complex" life. As is, apparently, the abiogenic origin of life itself. My best guess is that microbial life is at least as common as Arthur thinks it is, and that the principal reason that very robust biospheres like Earth's remain quite rare, and climax human-level intelligent-life conditions even moreso, is that these or other critical developments for the evolution of macrobiota and subsequently intelligence actually are relatively unlikely, and the universe just isn't quite old enough yet for them to manifest widely. Surely, we can surmise that as vast as the universe is known to be, as here on Earth, complex biospheres, including ones which have given rise to human-level intelligent beings, exist elsewhere in large numbers. But, and this is key from the human perspective, they are apparently very widely scattered. 

My last, and perhaps actually chief, criticism, is as follows. Arthur all but totally ignores the possibility that human-level intelligence itself, when it does evolve, is absolutely critical to the future history of biospheres from which it evolves. He blithely assumes that humans and their descendants will simply become extinct before advancing to a stage where they are spreading terriform*** life elsewhere in the Galaxy, and that we will never exceed the bounds of our own Solar system. My belief, which I think is reasonable inference not just gut feeling, is that if and only if the human species survives the current era, the spread of terriform life far beyond the confines of one star system will be extremely likely. I base this on two assumptions:  if we survive a few centuries, we will likely succeed in building self sustaining space habitats that contain more terriform biomass than the surface of the Earth, eventually. Further, we will likely figure out how to construct some kind of practical interstellar transportation (which could be generation ships or suspended animation, or, just possibly, quite fast in terms of fraction of light speed, drives). I take both of these developments to be generally more or less inevitable if technological societies evolve to the level where they can easily travel in and dwell in space near their home stars. The question then becomes how likely those developments actually are to occur, which translates to how prevalent technological societies are in the universe. And on that point, I hold forth two maxims. 1. Humans are very ingenious; our minds have evolved to the point that there really are no limits on what possible technology we can figure out and build in time; and 2. there is absolutely nothing in this scenario that is impossible. The same maxims should apply with respect to other human-level intelligent beings elsewhere in the universe. 

Arthur mentions virtually nothing discussed in this last paragraph. But they are crucial to his subject, which does purport to discuss the future of life. And if you generalize to other comparably situated intelligent species in a wider universe, the inference that even if we fail others will succeed is hard to avoid. 

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*Reference is to the influential but widely critiqued book, Rare Earth, Why Complex Life is Uncommon in the Universe, by Peter D. Ward and Donald Brownlee (2000, 2003).

** Referring to the evolution of nucleated cells, widely believed to be necessary for the evolution of so-called "macrobiota."

***As far as I know this is an original coinage. The term is meant to refer to life originating on, or descended from life originating on, Earth.