Tag Archives: Origin of Life

Are Gardens Fertile?

Cosmologists tend to think that the physics we see around us is not universal. There is instead a vast “landscape” of possible ways a local physics could be, and different (large far away) places in the universe embody or express these different physics.

When adjacent space-time places have different local physics, there must be a common “meta” physics that describes their border. This meta-physics will say how often places of one type lead to places of other types nearby, including “ends” where nothing is nearby.

Let us distinguish two special kinds of places:

  • Gardens support life and possibly civilization.
  • Fertile places tend to lead to more fertile places nearby.

The existence of any fertile place implies an expected infinity of connected fertile places. Thus when meta-physics maintains a one-to-one state map across a time dimension, there should be no finite upper bound to the entropy of a fertile place. Thus the entropy at a fertile place is always vastly lower than is possible, and entropy would increase in some local time direction. Since this low entropy should infect adjacent places, non-fertile places “close enough” to fertile ones should also have entropy increasing away from the fertile side. Thus we can explain our local “arrow of time” by assuming that our place is connected to a fertile place in our distant past.

Is our garden fertile? If both gardens and fertile places are rare, and these properties are not very correlated, then fertile gardens would be especially rare – it would be quite unlikely that our garden is fertile. In this case, while our universe is infinite, our future is finite, and will see and influence only a finite amount before our space and entropy run out.

Cosmologists today, however, tend to think that fertile places are not very rare. They expect places with a “positive vacuum energy” and a “low vacuum decay rate” to generate many “baby universes”, and that many of these baby universes also satisfy this description. In fact, they guess that our place here satisfies this description, and so is fertile. (This is, basically, Sean Carroll’s account of our arrow of time.)

But a whole lot of guess work goes into all this. For example, it could be that vacuum decay rates are much higher, and that baby-universe-generating rates are much lower, than they’ve guessed. My guess is that this property of being fertile is rarer than cosmologists now guess, which lowers the chance of our garden being fertile.

A correlation between being a garden and being fertile might result if civilizations tended to work to increase the rate at which their places lead to more places nearby. But it might be that for most gardens there isn’s much civilizations can do.  In which case if fertile places are rare, then most gardens are not fertile, our future is finite.

Finally, even if our place is fertile, it might be that the border between our place and other different places has no “hair” letting us send specific influences from here to there. In this case, our future influence would still be finite.

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Alien Life Info, But Not Status, Found

HooverFigure4a

A new Journal of Cosmology article says that sealed deep in the water-clay-full sort of (CI1 carbonaceous) meteorites that likely come from comets, one consistently finds forms that look visually and chemically like ancient bacteria fossils. Typical reactions:

This effort clearly falls into the category of “extraordinary claims” that require extraordinary evidence. (more)

Dr David Marais, an astrobiologist with NASA’s AMES Research Centre, said he was very cautious about jumping on the bandwagon. These kinds of claims have been made before, he noted and found to be false. “It’s an extraordinary claim, and thus I’ll need extraordinary evidence,” he said. (more)

Those are odd and intriguing formations, to be sure. … Contamination, no matter how unlikely, is a more mundane explanation than extraterrestrial life, and Occam’s Razor will always shave very closely here. We have to be very, very clear that contamination was impossible before seriously entertaining the idea that these structures are space-borne life. I’ll be honest: my own reaction is one of extreme skepticism. As it should be! All things being equal, I would take news like this with a very large grain of salt, and want a whole lot of outside expert analysis. (more)

The last one links to this explanation:

Extraordinary claims require extraordinary evidence because they usually contradict claims that are backed by extraordinary evidence. The evidence for the extraordinary claim must support the new claim as well as explain why the old claims that are now being abandoned, previously appeared to be correct.

Alas, these attitudes make far more sense in status terms than in information terms.

In status terms, it would of course be big news to hear that academia had declared its consensus that alien life had most likely been found. Academia’s public and patrons would take heed, and the academics associated with inducing that event would gain high status. So academics want to ensure that only folks with quite impressive academic abilities could gain such a prestigious honor. Thus they naturally want to that this honor goes to folks with extremely impressive data, methods, etc. And this paper, published in a low prestige journal by a low prestige academic, using solid but not especially difficult techniques, seems below that bar.

But in information terms, this new result does seem in the ballpark of tipping us over the threshold of thinking it likely than alien life has been found.

First, our prior estimate that alien life would be found in comet-based meteorites should have been pretty high. The idea that life came here from out there is a standard reasonable view: Continue reading "Alien Life Info, But Not Status, Found" »

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Aliens Not So Strange

If the Martian life form transpires to be eerily similar, this might only show that Life … in reality has very few options. … No sentient forms weaving their existence in vast interstellar dust clouds, farewell to bizarre filamentous species greedily soaking up the intense magnetic fields of a crushingly oppressive neutron star and on even Earth-like planets no forms that we might as well call conceptualized pancakes. … Contrary to received neo-Darwinian wisdom, life on Earth at any level of organization—from molecular to societal— will provide a remarkably good guide as to what ought to be ‘out there’.

So argues Simon Conway Morris, from inside view considerations. I think he’s mostly right, but based on an outside view.

Here it is: when relevant parameters can vary by large magnitudes, the most common type of thing is often overwhemingly more common. For example, processes that create and transmute elements vary greatly in their rates. So even though there are over a hundred elements in the periodic table, over 90% of all atoms are hydrogen, so the odds that two randomly selected atoms are the same element is >80%.

Similarly, since the influences on how many eyes a human has vary greatly across eye numbers, most humans have the same number of eyes: two. Most humans do not have the same last name, however, since rates of gaining or changing names do not vary by huge factors.

The same principle applies to life. Life might have evolved in a great many kinds of environments, based on a great many sorts of elements, and using many types of organization. To the extent that some environments are far more common, or are far more supportive of high rates of biological activity, most biological activity in the universe should occur in the few most common and supportive environments. Similarly if some elements or organizations are far more supportive of biological activity and innovation, most life should use those elements and organization.

I expect cosmic environments to vary enormously in both volume and in support for biological activity. I also expect some types of elements and organizations to be far more supportive of biological activity and innovation. I thus expect most life to be based on similar elements and organizations, to originate and be active and innovative in places similar to where our life orginated and is most active and innovative.

This view is supported by the fact that the assumption that life originates via the entropy of sunlight hitting “dust” predicts many cosmological parameters. In ’08 I reported:

This causal entropic principle so far successfully predicts dark energy strength, matter fluctuation ratio, baryonic to dark matter ratio, and baryonic to photon matter ratio! … A simple reading of the principle is that since observers need entropy gains to function physically, we can estimate the probability that any small spacetime volume contains an observer to be proportional to the entropy gain in that volume. … Exclud[ing] entropy of cosmic and black holes horizons, … ignor[ing] future observers getting far more efficient and aggressive in using entropy, … they estimate that, aside from decaying dark matter, near us most entropy is made by starlight hitting dust, and most of that is in the past.

Our life probably started from sunlight hitting “dust” (including planets). More quotes from Simon Conway Morris: Continue reading "Aliens Not So Strange" »

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Ban Mirror Cells

Imagine a mirror reversed cell, made of mirror-reversed molecules. If it gained energy via photosynthesis, or via special adaptations that enable it to eat ordinary life, the fact that it was immune to ordinary predators and disease would give it a huge advantage; it could take over much of the biosphere. Sounds like a good reason not to make mirror cells right? Unfortunately, there are now big efforts to develop mirror cells, because they’d be a handy biotech tool for pumping out lucrative mirror proteins. Yes this is a real gain, and yes there are ways to try to stop mirror cells from getting loose and destroying the biosphere. But really, the gains here seem easily outweighed by the risks. This is a pretty clear case justifying strong global regulation or bans. Alas, I can find no movement in this direction. Details:

A life-form … based on mirror-image versions of earthly proteins and DNA. … If it worked, those new cells … might also open up new avenues of discovery in materials science, fuel synthesis, and pharmaceutical research. On the down side, though, mirror life wouldn’t have any predators or diseases to limit its reproduction. …

A catastrophe was under way across the Charles River at Genzyme, one of the largest biotech companies in the world. … A virus that disrupts cell reproduction infected one of the bioreactors. The entire plant had to be shut down. … When Church talks about mirror life’s quirky advantages, invulnerability to this kind of mishap is high on his list. “Viruses can’t touch a mirror cell,” … This makes mirror life a potential workhorse for biotech. … Church has been hacking the ribosome. … His plan is to make one that reads regular RNA transcripts of genes but can string together wrong-handed amino acids to form mirror proteins. … Church and his team have cracked the first step. … Last year his team got a synthetic ribosome to self-assemble and produce luciferase, the protein that makes fireflies glow. And he has a library of mutant ribosomes that have the right kind of sockets—they’ll accept mirror amino acids. This is where the money comes in. Some of the most valuable drugs are actually tiny proteins that include wrong-handed amino acids—like the immunosuppressant cyclosporine. To manufacture it, pharmaceutical companies have to rely on an inefficient and expensive fungus. A hacked ribosome modified to handle both normal and mirror amino acids could crank out the stuff on an industrial scale. …

Church thinks even bigger. A manufacturing ribosome would be great, but a fully domesticated mirror cell—able to synthesize more-complicated stuff—would change everything. … vats of virus-proof mirror cells could pump out biofuel, lay down nano-size organic circuitry, and even extrude organic cement foundations for skyscrapers. …

Of course, mirror life could also kill us all. … Just as viruses from our side of the mirror can’t infect it, mirror pathogens can’t infect us. … They might be poisonous, though. … To a mirror cell, … there’s just not enough nutrition for them in the wild. … On the other hand, if mirror cells somehow evolved—or were engineered—to consume normal fats, sugars, and proteins, we might have a problem. … Mirror cells would slowly convert edible matter into more of themselves. … If mirror cells acquired the ability to photosynthesize, we’d be screwed. … All it would take would be a droplet of mirror cyanobacteria squirted into the ocean. Cyanobacteria are at the base of the ocean’s food pyramid, converting sunlight and carbon dioxide into more of themselves … That would wipe out the global ocean ecology. …

“I would be the first to say that we shouldn’t make a photosynthetic mirror cell,” Church says. “But I’m reluctant to have a moratorium on something that doesn’t exist yet.” He says he’d build safeguards into his mirror cells so they’d perish without constant care. And the advances in synthetic biology required to transform those first delicate mirror cells into anything that could survive in the wild are even more remote.

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At Least Two Filters

Where lies the great filter, i.e., the obstacles that make it extremely unlikely that any one chunk of pre-organic matter originates a visibly expanding interstellar civilization? While it seems unlikely our ancestors passed through much of a filter in the last half billion years, our descendants may face a big filter in the next few thousand years, and there may have been big filters associated with the origin of life, the spread of life, the invention of complex cells, sexual reproduction, or multicellular life.

In many folks eyes, an elegantly simple resolution, which is likely because of its simplicity, is to assume there is just one huge filter: the origin of life. Assuming that first step is enormously hard allows one to think all the other steps are pretty easy. They wouldn’t be sure things of course, but conditional on a big enough origin-of-life filter, one wouldn’t have a strong reason to fear that common analyses underestimate future filters.

Unfortunately, the elegantly simple hypothesis that the great filter is mainly a big origin-of-life filter seems at odds with our best evidence. Why? Because if the spread-of-life step had the weakest possible associated filter, then life spreading must be easy. Over billions of years life could have spread to many star systems from its place of origin:

Life could spread across a galaxy via giant molecular clouds reliably collecting life from the stars they drift near, and then passing that life on to a few of the thousands of new stars they create.

If over billions of years life spread to many hundreds, or even billions, of star systems, and no substantial filters stood between arrival of life near a star, and its eventual development of advanced technical civilizations like ours, then why would we now see no any evidence of other civilizations? Yes it is possible that we are the very first, but that hypothesis is of course unlikely by default.

It seems to me that if the great filter is to consist of just one big step, the only plausible possibility is the development of multi-cellular life. All the steps before that one seem able to spread to other star systems via single-celled life hidden in dust, and it seems we haven’t had a big filter step since the multi-cellular innovation.

So if the idea of just one big filter appeals to your sense of elegance, you’ll have to presume that life, including complex life with sexual reproduction etc., is very common in our vast universe, but that Earth is one of the handful of places in all that vastness with multi-cellular life.

If you don’t find that plausible, well then you’ll have to grant there are at least two filters. And if two, why not three? So you must find the possibility of a third filter in our future plausible; beware future filters.

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New Hard Steps Results

If planets like ours are common but intelligent life like ours is rare, then it should be rare that life on a planet evolves to our level of development before life is no longer possible on that planet.  If Earth was “lucky” in this way, and if life had to go through a series of stages of varying difficulty to reach our level, how long should each stage have taken?

Now these stages could be of quite different difficulties, taking quite different unconditional expected times to complete.  But back in ’98 I noticed (and posted) an interesting non-intuitive result: if each stage is “exponential,” with a constant per time chance c to jump to the next level, then all “hard step” durations are similarly distributed, no matter what their relative difficulty.  (Joint step times are drawn from a uniform distribution.)  So we should see a history of roughly equally spaced hard step transition events in Earth’s history.

Prof. David J. Aldous, of U.C. Berkeley Dept. of Statistics, has just posted some generalizations of this result. While my result generalizes trivially to any per time success chance function C(t) that is nearly a constant C(t) = c near t=0, Aldous also generalized my similarly-distributed result to any function that is nearly linear C(t) = c*t near t=0.  He also generalized my result to any arbitrary tree of possible paths.  Each link in the tree can have arbitrarily varying difficulty, at each node in the tree many processes compete to be the first to succeed, and the one that wins this contest determines the system’s direction in the tree.

While Aldous warns us against over-reliance on simple models, this does I think gives a bit more reason to expect our history to consist of a sequence of roughly equally spaced hard step transitions.

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Silencing Outsider Status

Me last week:

Paul Davies, chair of the group that decides what SETI scientists will do if evidence of aliens is ever found, thinks … until scientists can say something to the public with great (~99%) confidence, they should say nothing. … Most early low-probability signs … being false alarms is “damaging to the credibility of science.”  So until scientists can confidently say that an asteroid will hit us or that we see aliens, they should just whisper to each other. … One might justify this confidence-or-silence policy by arguing … reporters are biased to present low probability news as if it were high probability.

Today’s Post:

NASA … reopened a 14-year-old controversy, … reaffirming and offering support for its widely challenged assertion that a 4-billion-year-old meteorite that landed thousands of years ago on Antarctica shows evidence of microscopic life on Mars. … Fourteen years of relentless criticism have turned many scientists against the McKay results, and the Mars meteorite “discovery” has remained an unresolved and somewhat awkward issue.  This has continued even though the team’s central finding — that Mars once had living creatures — has gained broad acceptance. …

Critics had said that the magnetites could have just as easily existed without bacteria or biology — that they sometimes form as a result of the shock and searing heat that could come, for instance, from an asteroid strike. But … [a] recent paper … reported that the purity of the magnetites made that explanation impossible. … “All the criticisms of our original paper got widely distributed, but when we did the work to prove the critics were wrong, it hardly made a ripple. … We’re now in a position to say we’ve knocked down all the criticisms — and our biological explanation is the one left standing.” …

At the conference, a leading cautionary voice in astrobiology proposed that a special protocol be established to oversee release of any journal articles making dramatic extraterrestrial claims. Andrew Steele … compared the absence of astrobiology review with the formal procedures set up by scientists involved with the search for extraterrestrial life, or SETI.  He said that SETI leaders understood the societal sensitivity of their work and that it was time for researchers in astrobiology “grow up and do the same.” (more)

Yet another voice for muzzling!  It seems clear to me that scientists do not usually insist on such high standards of confidence for publication.  Most Research Findings Are False seems pretty clear evidence, as does the high rate of celebrated new medical treatments that are later repudiated, and the very low marginal health-effectiveness of medicine.  I suspect I see similarly low standards for publications that are pro-global warming, or that warn of low science funding or manpower.  If the standard of evidence for publication varies with the topic, we can’t explain it via a generic tendency for reporters to exaggerate findings.  So what explains this variation?

Here I’ll channel Tyler Cowen, and suggest this is mostly about how real events echoing stories we tell change which intellectuals get more status.  Think of all the movies you’ve ever seen of an outsider intellectual unfairly rejected by establishment scientists.  Evidence of aliens, or a Really Big Disaster are prototypical.  Well establishment scientists see those movies too, and they don’t want real stories like them to appear in the media. They correctly perceive, for example, that a story confirming aliens would raise the status of UFO nuts, relative to establishment academics.  Similarly, news about a really big disaster would raise the status of “the sky is falling” outsiders.

On the other hand, establishment academics correctly perceive their status would be raised, relative to outsiders, by more stories of promising new medical treatments, of the seriousness of global warming, of the need for more science funding, or that a new result “might lead to a new theory of everything.” Even if such stories turn out later to be wrong.  Why?  Because we hear many similar stories about heroic scientists discovering treatments, or warning of enviro disaster, and few stories about such scientists being later wrong.

I see two effects:

  1. There are some long standing disagreements between insider and outsider intellectuals in our society, and any news that confirms outsider claims raises outsider status.
  2. News about a real event about you that matches a commonly-told story in which you’d be a hero, raises your status.   If that news is later reversed, that won’t reverse your status, if there aren’t commonly told stories about you being a villain in a news reversal story.
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Eerie Errors

Paul Davies’ new book The Eerie Silence is good overall, and probably great for someone who hasn’t read ten other SETI books.  Two gems:

1) Perhaps our descendants will not be forced to adopt future ways:

It is clear that different forms of microbes can complete in the same space for many of the same resources, without one form ever eliminating the other. [p59]

2) Opinions on big questions often fluctuate more than added info justifies:

In spite of these dampening facts, belief in extraterrestrial life is now widespread among scientists.  So what has changed since the days of pessimists like Crick, Monod and Simpson?  Curiously, very little on the actual scientific front. … None of the scientific discoveries of the past half-century have greatly altered what we know, or don’t know, about life’s seemingly freaky nature.  The change in sentiment is due, I believe, to fashion rather than discovery.  At a time when physicists freely speculate about extra dimensions, anti-gravikty and dark matter, and cosmologists propose multiple universes and dark energy, speculation about extraterrestrial life seems tame by comparison.  [p32]

I’ve similarly suggested opinions on if the universe is infinite also fluctuate too much.  Let me also point out some errors in the book:

A) This news on our ignorance of early Earth life isn’t reflected here: Continue reading "Eerie Errors" »

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No Early Earth Life?

We know a lot less about early Earth life than I’d thought:

Two decades ago [Schopf] … was investigating … 3.5-billion-year-old rocks that are among the oldest on Earth. In 1993, he announced that they contained 11 different types of “microfossil” that looked for all the world like modern photosynthesising cyanobacteria. … Other 3.5-billion-year-old Australian rocks contained rippling structures that looked like fossil stromatolites. … Astonishingly soon after our planet formed some 4.6 billion years ago, photosynthesising bacteria were widespread. This emerging consensus lasted only until 2002, when palaeontologist Martin Brasier of the University of Oxford unleashed a barrage of criticisms. …

New lines of evidence mean that the oldest undisputed signs of cyanobacteria are now fossils found in rocks from the Belcher Islands in northern Canada dating from just 2.1 billion years ago. … In this “great oxygenation event” of around 2.4 billion years ago, levels rose from around 1 per cent of today’s levels to perhaps 10 per cent.  Our best guess is still that cyanobacteria were around some time before this event. Persuasive evidence is converging on a date around 2.7 billion years ago. … The modern nitrogen cycle kicked off around this time. … The great oxygenation event … seems to have been the forerunner to a “snowball Earth”….  And yet the great oxygenation was impermanent. … By 1.9 billion years ago, levels of breathable oxygen in Earth’s atmosphere were back down to the merest trace.  We don’t know why. …

Oxygen levels in the atmosphere soon recovered again … [at] a new equilibrium, at about 10 per cent of present-day levels. …. This time, the oxidative weathering of sulphides on land filled the oceans with sulphate. That in turn fuelled a hardy group of bacteria that … [turned oceans] into stinking, stagnant waters almost entirely devoid of oxygen. … An extraordinary stasis in Earth’s environment … dubbed the “boring billion” [years followed].  … What happened to the oxygenic utopia in which life supposedly grew and prospered, evolving the complex cells that went on to make up animal and plant life? …  It probably never existed. …  [Those] stinking oceans were the true cradle of life. Evidence behind this idea includes the fact that mitochondria, the powerhouses of all complex, oxygen-respiring “eukaryotic” cells today, were once far more varied, sometimes “breathing” sulphur or nitrogen instead of oxygen. ….

Earth’s anoxic stasis was broken in the end by a dramatic series of snowball Earths, indicating bursts of oxygen, beginning about 750 million years ago and recurring over the following 100 million years. They broke the eternal loop: soon afterwards, oxygen levels shot up and never looked back. Animal life soon exploded onto the scene.  What made the difference this time? One intriguing possibility is that it was down to the organisms that had evolved in a leisurely way during the boring billion: terrestrial red and green algae and the first lichens.

More here.  This will clearly require a rethinking of my hard steps of life analysis based a now outdated event timeline.

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Cosmic Clump Coincidence?

Now this is just weird: the Zodiac, an apparent ring of distinct extra bright stars centered on us, is not an illusion – it really exists out there.  Called Gould’s belt, it is ~1000pc (parsec) in diameter, we are within about 100pc of its center, and it formed together 30-60 million years ago:

GouldsBelt

Some think it formed when a clump of dark matter, massing about ten million suns, passed through a molecular cloud, an event they say should happen every ~300 million years.  (Clumps pass elsewhere more often – Smith’s cloud, massing a hundred million suns, is passing right now. There should be about a thousand  such clumps near our galaxy.)

Since our galaxy’s diameter is about 40,000pc , the chance that the most recent clump would hit that close to us was roughly one in (40,000/200)2, or one in 40,000.  Since about a tenth of galaxy area has molecular clouds, the chance the most recent clump to hit a cloud would hit that close to us is one in 4000.  Coincidence?  Consider this plot from Jerison:

brainsizehist

This dark matter clump hit us just about when the last big burst of max brain size growth began on Earth, with primates ~50 million years ago.  Yes, it is hard to see how a rare dark matter clump passing near could induce a primate brain growth spurt, so it is probably coincidence.  But big apparent coincidences should at least make us pause and ponder.

More details: Continue reading "Cosmic Clump Coincidence?" »

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