David Brin is a Sentient Developments guest blogger.
This rather lengthy posting is for all you astronomy junkies who are interested in the Origin of Life question... but also to offer you a glimpse of the seamy and immature side of scientific paper publishing. Warning, it is not an ankle-deep puddle-splash. You'll need to wade in, at least hip-deep.
Recently, I was asked to offer a peer review of a paper submitted to the "Journal of Cosmology," an online venture backed by the famed astronomer-iconoclast and former colleague of Fred Hoyle, Chandra Wickramasinghe. Despite a new-Agey look, I had high hopes, perhaps because of the journal's name, or because the chief editor is a neighbor of mine and works in a building where I did graduate school.
Alas, my hopes ebbed as I ready the paper: "Life on Earth Came From Other Planets," by Rhawn Joseph, Ph.D. (His bio, at the end of the article, is about as vague as could possibly be - but one should judge a work by its content, which I proceeded to do. Unfortunately, I found much to fault in the lengthy paper, laying down details in the work of many hours.
What I did not expect was for the editor to thereupon go ballistic on me! Accusing me, in emotion-drenched terms, of defaming and insulting Dr. Joseph. In science, one isn't used to having an invited peer review rejected in such a manner, amid vague ad hominem attacks, without actually quoting or citing any of the purportedly unfair passages in question. Having good-naturedly and generously given many hours to this futile exercise, I blinked in appalled wonder as, without any basis, the editor claimed that I had called Dr. Joseph a "Creation Scientist."
Generally, such misunderstandings are settled by asking the question: "Show me where I actually said that, please?" But no such specifics were forthcoming, only more vituperation.
So, why am I even bothering to report on this event, here? Because we are in the internet age. The topic of Dr. Joseph's paper is an interesting one. Indeed, despite some naivete and glaring omissions, it also contains some thought provoking and entertaining passages. Above all, the effort that I put into appraising and analyzing -- and, in part, refuting -- his thesis ought not to be wasted. There are those who may be edified.
(Note, an inveterate re-writer, I edited some of these passages from the version submitted to JoC, for clarity or readability. However I made NO changes in any passages that might have been the skimmed-misinterpreted sources of the editor's strange vitriol. I leave it to anyone to find justification for claiming that I clearly "hate Dr. Joseph." (???) )
So make of this what you will. Or not. Don't feel obliged. Believe me; there are far more important things going on, in science, right now. All told, I wish I had never heard of these guys.
==== David Brin Ph.D appraises and critiques "Life on Earth Came From Other Planets," by Rhawn Joseph, Ph.D., Journal of Cosmology (2009) =======
While this paper is interesting and fun to read -- and shows an ambitious eagerness that does Dr. Rhawn Joseph credit -- there are some glaring faults. The central one is that this article creates a "just-so story" about Earth's early seas having been seeded by the process known as "panspermia." This notion credits the origin of Earth's biology not to the evolution of cells out of proto-biochemistry, but to the arrival of spores or other living material that may have crossed interstellar space from some earlier biome, a concept that goes back more than a century to Svante Arrhenius.
Dr. Joseph's core innovation is to propose that these seed materials were driven into the coalescing cloud of dust and gas that formed our sun and solar system by the very same supernova that created most of the heavier elements out of which the Earth was formed. The star that went supernova is posited to have had planets that were demolished by the cataclysm, but without destroying all dormant life-material, since those planets would -- Joseph proposes -- have been driven outward some distance, earlier, during an intermediate, giant star phase, before the supernova.
An entertaining scenario, indeed. But even were it to be plausible, without the flaws that I shall elucidate, it would nevertheless remain just a story, one of many ways that dormant life-material might enter interstellar space and eventually arrive at Earth. Hence, it would merit only one place among many such scenarios, rather than being placed on a pedestal, as The Answer.
Indeed, the literature of panspermia speculation offers quite a list of alternative sources of drifting life-material that might enter the atmosphere of an early water world, such as the Earth was (presumably) half a billion years after its formation. For example, Fred Hoyle and Chandra Wickramasinghe, and separately Nobelist Hannes Alfven, posited that large COMETS, measuring above ten kilometers in radius, might -- soon after their formation amid supernova debris -- contain copious amounts of the radioactive isotope Aluminum 26. Decay of this substance might thereupon heat and melt internal spaces and fill them with liquid water, protected from space conditions by insulating layers of ice. Within these micro-oceans, water, energy and necessary elements might mix and create pre-biotic or even life-supporting soups. While individual comet chambers might seem small, compared to a planet's ocean, the sheer number of such comets is staggering to contemplate, perhaps pervading every stellar system, not only those with earthlike planets equable, continuously habitable zones. This potentially vast volume of watery reactor vessels led some to suggest comets as the true test-tube sources of life in the universe.
(Note: my own doctoral work was on comets and my novel HEART OF THE COMET featured discussion of these issues.)
Offering vast amounts of liquid water volume for pre-biotic chemistry is not the only advantage of this earlier model. In addition, we are not asked to believe that the seeding material will survive a nearby supernova.
Nevertheless, I bring up this previous scenario not so much in order to contrast it against Dr. Joseph's proposal, as to point out that such scenarios are abundant. It was Joseph's duty to both understand all competing theories and present them in full light. His mere mention of comets as delivery systems, to inject life-seeding material into the early Earth, was insufficient and remiss.
Before getting down to nitty gritty specifics of Joseph's particular scenario, let me pause and step even farther back. Dr. Joseph's central tenet -- contending that life cannot arise from non-life, and hence must be traced farther back in time, to earlier living sources, is made plain where he says: "Given the complexity of a single-celled organism and its DNA, the likelihood that life on Earth began in an organic soup is the equivalent of discovering a computer on Mars and claiming it was randomly assembled in the methane sea."
(Let us put aside the strange "methane sea" non-sequitur... could he have been thinking about Titan?... and proceed.)
This premise, shared by the so-called Creation Science movement, is not well thought-out. It is one thing to suggest that there are missing steps, between the complex precursor molecules derived so far, in later versions of the Miller-Urey-Orgel experiments, and truly self-sustaining cellular life. Skeptics about the missing steps may turn out to be right, after all.We'll see.
It is quite another thing to trot out this old horse chestnut -- that in order to arise out of pre-biotic material, life must self-assemble completely randomly, directly from raw materials into all the perfectly interacting gears and wheels of a living cell. Anyone who pushes that line simply has not allowed himself to grasp the well-observed phenomenon of Successive Selection and Accumulation, which renders such "clockmaker" arguments not only irrelevant, but ignorant.
Let me clarify this point, to eliminate any chance of misunderstanding. I am not saying that the Standard Model maintained by the vast majority of working evolutionary biochemists is automatically true, just because it is the majority consensus! Standard Models have been proved wrong, on occasion, in the history of science. Nevertheless, those who rebuke the consensus in any scientific field do bear the burden of proof. Above all, they should be able to describe -- even paraphrase accurately -- what that consensus view is and what its strongest supporting arguments may be, before seeking to systematically disprove those arguments.
In this case, Dr. Joseph is not merely suggesting a method by which Earth MAY have been seeded by interstellar life. He ridicules the very notion of "life from non-life" dismissing the majority view with little more than a rhetorical shrug. That is not how rebel scientists systematically disprove a standing consensus.
Please note that I do not go so far as to class Dr. Joseph categorically with Creationists, any more than Chandra Wickramasinghe was one. Both men avow belief in actual astronomy in a vast and ancient, physics-propelled cosmos. Indeed, Wickramasinghe did accept Successive Selection and Accumulation; he simply believed that the early Earth lacked sufficient time and working volume to accomplish the task. His favored cometary chambers, on the other hand, would. Or so he contended.
Dr. Joseph, in contrast, appears to simply be pushing the critical question further back in time. Allegorically, it is like claiming that the Earth-supporting turtle stands on the back of another turtle, then another, "all the way down."
So let me put the question: if life did not arise from non-life on the Earth itself, then when and where did it begin? Alas, if we go back too far, we enter an era when the Milky Way's metallicity would be too low to support life. Indeed, that wall is encountered only one stellar generation before our sun. It had to start somewhere!
As for Dr. Joseph's particular proposal, there are problems which I'll attempt to shed light upon... though for lack of time, I'll be brief.
1) His scenario posits that our solar system condensed rather immediately after interstellar space was seeded with detritus from a supernova. While it is true that supernova-generated isotopes were the crucial ingredients for rocky planets and for later generation, metal-rich stars like our sun, this scenario is implausible. Propulsive dispersal from a supernova encompasses many light years and substantial periods of time. Condensation episodes are thought to take place only later, after the ejected material comes into contact with pre-existing molecular clouds, whereupon hydrodynamic complexities can occur. We are talking about vast distances of many parsecs. The odds of any pre-existing planets, formerly in orbit around the supernova star itself, being involved, would seem -- well -- astronomical.
2) That fact, plus the rarity of supernovas themselves, means that Dr. Joseph is proposing a "rare life" scenario, and hence a fairly uncommon position among panspermia thinkers, who tend to envision life spreading everywhere. I am not objecting to this, per se. He is welcome to hold that life is rare in the cosmos. There are, of course, philosophical problems, e.g. the Anthropic Principle, that all such rare-life theories must face, compared to hypotheses based upon plenitude. But that does not refute him.
3) In any event, there are astronomical problems with his theory. Most supernovae come either from very large stars or else stars that tightly co-orbit with white dwarves. Neither of these are the type of solar system where one would generally expect to find circumstances friendly to life. The big stars only last some tens of millions of years, hence what can we expect from their planets, which might not even have time to cool and form seas?
In the other class of supernovae, the white dwarf companion would mess up orbital mechanics and would have created many earlier violent episodes. Dr. Joseph should do a better job explaining why such systems seem more likely to engender life than our own placid, early seas, orbiting a calm, long-lived and stable sun.
4) This one is lethal. Let me quote from Dr. Joseph:
"It is generally believed that our sun was created within a nebular cloud produced by a supernova nearly 5 billion years ago. A protoplanetary disc formed from the remnants of the nebular cloud surrounding the new sun, thereby giving rise to the planets of this solar system (Greaves 2005; van Dishoeck 2006)."
Alas, this view is simplistic, misleading and simply flat-out wrong. Experts on the material that first formed in the solar system -- found in tiny inclusions in the oldest meteorites -- have determined that our solar system coalesced from a cloud that contained contributions from AT LEAST THREE, AND POSSIBLY FIVE OR MORE INDEPENDENT NUCLEOSYNTHETIC SOURCES. (The Wasserberg Lab, at Calktech.) In other words, there was not just one supernova cloud but an amalgamation that stewed with contributions from several earlier supernovae and/or novae, over an extended period.
Hence, the amount of mixing time required would be hundreds of millions of years. Since the galaxy, at our distance from the center, takes about 200 Myr to complete a rotation, any conceivable association with the specific planets that once circled a particular supernova would long have smeared out, leaving the odds of Dr. Joseph's scenario happening in the realm of spooky coincidence.
Of course, there may have been drifting particulate matter, instead of larger bodies, dispersed throughout the clouds. But seriously. In that case, who needs a supernova? Living worlds would shed such stuff through meteoritic impacts etc.
I could go on. Alas, I haven't the time. Suffice it to say that there are problems with this scenario.
These problems do not invalidate the notion that panspermia-seeding might have set life in motion on our planet. I find that general concept plausible in a very broad way -- though not a leading candidate. Top position -- until someone comes up with good reason to change -- goes to the Standard Model consensus or life-from-nonlife in Earth's early seas.
Nevertheless, I'll maintain an open mind. Certainly, if the galaxy turns out to be rife with comets that were once great big aqueous/organic reactor vessels, one could imagine them delivering precursors in copious quantities, swamping our own planet's own creative fecundity. It could happen, perhaps.
No, the devil is in the details. And Dr. Joseph's details are, unfortunately, unconvincing.
I do compliment Dr. Joseph for his initiative, enthusiasm, and eagerness to explore fresh ideas. I found his paper interesting and entertaining... but, ultimately, lacking.
With cordial regards,