No-One Has a Head

In a 2007 paper, Charles Lineweaver develops Rare Head Theory:

We can use Fig. 4 to identify trends in the evolution of life, or convergences on some specific feature, whether it be E.Q., N.Q., olfactory lobe size or eyeballs. First we randomly select a few of the ~60 branches shown. Then we determine if two or more of them have independently evolved the feature of interest. For example, human-like intelligence probably depends on the existence of heads. Thus, we want to know if the tree of life shows any convergence towards heads. If heads were a convergent feature of evolution one would expect independent lineages to evolve heads. Our short twig on the lower left labeled “Homo” has heads, but heads are found in no other branch. Our two closest relatives, plants and fungi, do not seem to have any tendency toward evolving heads. The evolution of heads (encephalization) is therefore not a convergent feature of evolution. Heads are monophyletic and were once the possessions of only one quirky unique species that lived about six or seven hundred million years ago. Its ancestors, no doubt possessed some kind of proto-head related to neural crests and placodes (Wada 2001, Manzanares and Nieto 2003).

Drake (2006) stated that “[intelligence] is not a fluke that has occurred in some small sub-set of animal life.” However, Fig. 4 shows that intelligence, heads, even all animal life or multicellular life, may well be a fluke that is a small sub-set of terrestrial life. One potential problem with this conclusion: It is possible that existing heads could have suppressed the emergence of subsequent heads. Such suppression would be difficult to establish.

As they say, “as they say, read the whole thing”. I’m adding “The Subsequent Heads” to my list of potential transhumanist band names.

Sun Fine-Tuned?

New Scientist reports that Charles Lineweaver and others looked at 11 properties of the Sun and calculated that their combined “typicalness” relative to nearby stars is actually above average, concluding that the Sun has no properties fine-tuned for life. If so, there goes yet another potential part of an explanation for the Fermi Paradox.

The paper turns out to be on ArXiv, and there are some of the usual annoying interpretation-of-statistics issues.

The sun is heavier than 95% of other stars, and it’s been suggested this has an anthropic explanation; but the authors argue that because a joint chi-square test on all 11 independent properties comes out below average, the high mass is apparently a result of random chance.

If you ask me, that’s pure Bayesphemy.

The paper itself states:

Mass is probably the single most important characteristic of a star. For a main sequence star, mass determines luminosity, effective temperature, main sequence life-time and the dimensions, UV insolation and temporal stability of the circumstellar habitable zone (Kasting et al. 1993).

So what’s happened here is they’ve combined the data on the Sun’s atypically high mass with data (and attendant randomness) on ten other, less relevant properties. I don’t want to think about the math right now, but it seems intuitively that if you add enough properties that don’t do anything to a property that does do something in a joint chi-square test of the kind the authors used, you always have a decent shot at “showing” they don’t have a combined effect regardless of how strong the one real effect is.

Besides, if you’re interested only in the effect of mass, then how can knowing all the other properties (which are, again, independent of mass) tell you anything relevant? There’s just no information in them. I guess there could be if for some reason your probabilities for the proposition “unusual X is required for life” were positively correlated for different X. I guess if you were relying on someone’s authority when they said “high mass is important”, that person’s authority would be undermined by the evidence that other properties are unusually typical and so they may be cherry-picking properties.

Another thing I don’t immediately see them addressing is whether some properties may have been fine-tuned to be not too far from the typical range. Maybe that’s theoretically implausible in all 11 cases.

I’m not too sure of my thinking here; expect sneaky edits.

Regardless of Bayes gripes, the paper is interesting and informative. Although Lineweaver seems to be on the wrong side of the ET debate, I recommend his other stuff.

Awful Wastes of Space

Everybody says it’s a small world, nobody does anything about it.

In the words of Carl “awful waste of space” Sagan[1]:

We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That’s here. That’s home. That’s us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam.

You know what’s an awful waste of space, though? Earth having a surface area that, given its mass and composition, is the smallest mathematically possible[2]. According to respected scientists, more than 99.99995% of the planet is at least one meter below ground. You couldn’t cheat humanity out of more living space if you tried. That’s intelligent design for you.

Fear not. Some intrepid futurists have stepped up to the plate. Robert Bradbury has done the calculations on what it takes to disassemble a planet — for Earth, it takes all the sun’s energy output for “just” 22 days. Space settlements have long figured in both science fiction and futurist analysis. An art project called Globus Cassus, pictured above, even imagines us turning the Earth inside out.

In reality, I expect long-run expansion will be mostly into resource-cheap virtual worlds. There’s probably enough building materials outside Earth to make billions and billions of little worlds, so instead of eventually remodeling our planet, we may end up keeping it for sentimental value. I’m not invested in either possibility. I just would like us all to survive this century, so we’ll be around to make the choice.

[1]Yeah I know, he didn’t deserve that.

[2]Yeah I know, it’s not really a perfect sphere.

Wastes of Hope

In an Overcoming Bias post earlier this year, Eliezer Yudkowsky argued lotteries are a waste of hope:

Which makes the lottery another kind of sink: a sink of emotional energy. It encourages people to invest their dreams, their hopes for a better future, into an infinitesimal probability. If not for the lottery, maybe they would fantasize about going to technical school, or opening their own business, or getting a promotion at work – things they might be able to actually do, hopes that would make them want to become stronger. Their dreaming brains might, in the 20th visualization of the pleasant fantasy, notice a way to really do it. Isn’t that what dreams and brains are for?

This probably applies to a lot of seemingly harmless beliefs. As an obvious example, the hope for a positive afterlife in many people displaces the hope for technologically-achieved longevity and happiness in this life.

SETI, which I’ve earlier argued won’t work, encourages us to imagine scientific, technological, and moral progress as well as cultural richness coming from other civilizations than our own. And as far as I can tell, SETI isn’t just a fantasy, it’s a superfluous fantasy. I’ll call this the Law of Earth-Originating Infallibility: There is nothing desirable, no invention or piece of infrastructure or good idea or work of art or tree of life or conscious mind, that could not eventually be created by Earth-originating civilization alone, provided that it successfully navigated this bumpy period of adjusting to promising-but-dangerous technologies.

Is the Hole Natural?

You may have heard the news that astronomers discovered a billion light year hole in space. It’s tempting to blame an expanding alien civilization, but I think the hole is natural. Here are some bad and good reasons why:

  • In the picture, the hole still seems to have some galaxies in it, and I would expect a posthuman civilization to eat all galaxies in its reach. But from what I can tell, the science doesn’t exclude the possibility of a completely empty gap.
  • In the picture, the hole seems potato-shaped. If the aliens expanded at the same speed in all directions, the hole would be spherical — or, depending on how you look at it, pear-shaped, because we see closer galaxies later in time. But again, from what I can tell, we don’t know much about the hole’s exact shape. And there could be explanations for the wave having a different speed in different directions, like differences in density.
  • We see the gap as it was 6-10 billion years ago. That’s early in the history of the universe. Is it too early for civilizations to have formed? According to Charles Lineweaver, “68% of earths in the Universe are between 3.3 and 9.3 Gyr old while 95% are between 0.6 and 10.5 Gyr old”. So it doesn’t seem completely out of the question.
  • Why didn’t the colonization wave make the hole even bigger? Keep in mind that the farther out we look, the more into the past we see. If light from there is just arriving, probes couldn’t have arrived yet, and neither could evidence of further colonization. So in theory, the hole could be a lot bigger now than we see it. If expansion happens at almost the speed of light, the edge will reach us in only millions of years. But although this is possible, it’s a major coincidence. If colonization waves are really that fast, then the probability of catching one in action is tiny. And if expansion is much slower, explaining how they already colonized a billion light year blob becomes tough.
  • The prior probability that colonization waves emerge rarely enough to solve the Fermi paradox but often enough for us to encounter one is quite small.
  • Finally, from how I understand the experiments, we know two things about the hole: there are few radio wave-emitting galaxies there, and the cosmic microwave radiation from that direction was cooled because the mass in the hole went missing. I have no idea whether Matrioshka brains or whatever it is these guys build would emit a lot of radio waves. I do think removing all mass from a billion light year blob would require magic physics.

As you may have noticed, a lot of “I don’t know”s remain. I would be grateful if someone with more expertise could clarify.

Wouldn’t it be ironic, by the way, if the first proof of alien life were an immense radio silence?

Nick Bostrom on the Great Filter

Nick Bostrom recently put a popular lecture on his site arguing that the discovery of extraterrestrial life would be very bad news, because it would mean the Great Filter, meaning the set of difficult developmental steps that have stopped aliens from colonizing us, could be mostly in our future. I don’t really buy the argument. It seems to me that both friendly and unfriendly technological singularities would set off colonization waves; unfriendly singularities, while an existential risk, are not a filter candidate. So what’s left? Maybe certain molecular nanotech disasters (that do not involve AI), biotech disasters, and any scenario where humanity collapses gradually without getting into space. It’s hard to believe that, from information about the average alien civilization alone, we could conclude that there’s much room for these to do a lot of filtering in our case — more than 90%, say. If the evidence points toward there being a strong filter late in the development of a typical civilization, the best conclusion might not be that we’re also doomed; it might be that, apparently, we’re not a typical civilization.

Drake Was Wrong

(Followup to The Case for Axenism)

The Drake Equation expresses the number of currently communicating civilizations as a product of parameters like the rate of star formation, the fraction of Earthlike planets that develop life, and a civilization’s average lifetime. What very few people realize is that the equation assumes a steady-state model in which every civilization goes through the cycle of being born, sitting on its home planet broadcasting for some time, then dying. Specifically, it assumes that no interstellar colonization ever takes place. As I’ve argued, this assumption is clearly false. That means the Drake Equation is also false — it’s not just a rough approximation, it’s not just hard to estimate, it’s false in the sense that the left-hand side and the right-hand side have almost nothing to do with each other.

Let me illustrate this with an example. Assume that 5000 Earthlike planets are formed every year, 1/10 of Earthlike planets develop life, and 1/10 of planets with life develop a civilization that broadcasts for 1000 years, then stops. Based on Drake’s equation, we’d conclude there are 50,000 civilizations broadcasting. Except I didn’t tell you that the third civilization that popped up sent a wave of self-replicating probes and colonized 99% of all stars in the galaxy. Oops! Now the two sides are off by at least two orders of magnitude.

There are two ways to save the Drake Equation.

One, if you take everything literally — if by “the fraction of Earthlike planets that develop life”, you literally mean the fraction that develop life and don’t get colonized before that point — then the equation is a tautology. The advantage of tautologies is that they’re true. However, no one interprets the parameters this way. Doing so makes them impossible to estimate except by setting up a dynamic model, and makes the whole approach more or less useless.

Two, an equation very much like Drake’s can be used to estimate the probability that at least one civilization pops up in a particular region. This avoids problems caused by civilizations (and their precursors) interacting.

contact THIS, bozos!

The Case For Axenism

no wai!

What’s “axenism”? I admit I just made the word up, but etymologically speaking, axenism is to atheism what xenology is to theology. An axenist is an unbeliever with respect to extraterrestrial intelligence one who thinks alien civilizations don’t exist, at least not anywhere in our galaxy.

So why do I think alien civilizations don’t exist? There are two key observations to make.

First, when we split the probability for extraterrestrial intelligence into several factors à la Drake (e.g., the probability for simple replicators to arise, and the probability for life to develop intelligence), pick some reasonable-sounding estimates, and multiply them together, the order-of-magnitude uncertainties add up to a very broad range of possible numbers of alien civilizations anything from thousands per galaxy to less than one per region the size of our observable universe.

Second, the total lack of evidence for extraterrestrial intelligence suggests that among the all the many possible numbers of civilizations compatible with Drake-style calculations, very low numbers are the most likely to be right. As Fermi observed, if they were out there, they would have been here, and we would have noticed, or more likely failed to exist in the first place.

In short, not only is axenism compatible with all our knowledge, there is strong evidence in its favor.

Of course, various people disagree with various parts of this story.

  • It’s tempting to note that we humans form a technological civilization and conclude that, apparently, technological civilizations must not be that improbable. This gets into sticky issues of anthropic reasoning, on which philosophers disagree. Being a technological civilization is always what a typical technological civilization observes, no matter how rare technological civilizations are (it’s a problem if there aren’t any at all, but the universe is extremely big at least, and quite possibly infinite). Some infer from this that the information can be thrown out entirely. Others do think we should favor hypotheses that predict many technological civilizations. Even then, if the rest of my case holds, it’s a puzzle why we came into existence so late. Humanity’s time-of-birth seems to be a typical moment in a mostly empty universe where civilizations don’t interact until very late, if at all; it seems to be a highly atypical moment in a universe where many civilizations pop up as soon as conditions allow, then colonize their future light cone.
  • Some people might say the biological study of evolution and the origins of life tells us the probability of life eventually popping up on an Earthlike planet is quite high. If this is true, I would love to be enlightened. Creationist comparisons with tornados in junkyards are, of course, rubbish. But that’s still consistent with abiogenesis being extremely improbable. To the best of my knowledge, biologists are not able to confidently state any lower bound on the probability for abiogenesis, of the kind that shows it has to happen on at least, say, one in ten billion Earthlike planets.
  • It’s also sometimes claimed that, since highly intelligent behavior evolved in different species (primates, dolphins, etc), it must not be that improbable. Perhaps, but it could still be the case that the step from animal intelligence to full-blown human-level intelligence is very rare.
  • There is the argument that life arose on Earth early in the available window of opportunity, which is more likely if life is probable than if life is improbable. This argument is much less impressive if, as seems very possible, several hard steps were needed. In that case, we would expect them to be about evenly spaced. It also fails if Earth life originated on Mars, which is claimed to have been suitable for early life long before Earth was.
  • The claim that interstellar (even intergalactic) travel is infeasible is absurd. The problem of astronauts dying can be solved through relativistic dilation, generation ships, life extension, uploading, or sending artificial intelligence. The amount of resources required is huge relative to the present-day economy of Earth, but tiny relative to the economy of a solar-system-encompassing civilization, and tiny relative to the returns.
  • The claim that nobody would want to colonize the stars is absurd. It takes only one, as they say; self-replication will do the rest. Most or all advanced civilizations will prefer certain configurations of matter to others. Star systems have building materials, energy, perhaps information, potential humanitarian disasters, potential threats. In civilizations where groups and individuals vary in their expansionism, the expansionist ones will tend to dominate in the long run. The “Zoo Hypothesis” that aliens are keeping us in the dark on purpose requires very strange motivations.
  • Famous SETI researcher Jill Tarter responds to the question “then where are they” by saying something along the lines of “maybe they are here; maybe there are probes messing around in the asteroid belt and we can look for them”. This makes her a UFO believer, except at a slightly greater distance, and on no empirical evidence rather than flawed empirical evidence. Her suggestion explains nothing at all; the mystery is not literally why they’re not here; it’s why, in the hundreds of millions of years that they’ve had, they haven’t done anything, here or elsewhere, with visible or life-eradicating side effects.
  • Some have suggested all complex life in the galaxy is periodically toasted by gamma ray bursts or other disasters. That could be part of the explanation why we haven’t yet been visited, but among other problems, it doesn’t really explain why there’s no wave from any other galaxy.
  • Lastly, there are the nakedly religious objections that make no rational sense whatsoever. As Carl Sagan put it in Contact, if there were nobody else out there, wouldn’t that be an awful waste of space? Well, yes. And by that reasoning, Saturn is made out of strawberry and lemon ice cream, and its rings are delicious wafers. As Sagan knew perfectly well, Nature is indifferent to human concerns. Wasting stuff is just what it does. If the emptiness of the universe bothers us, we will have to send colonization waves and fill it with fun and beautiful things ourselves.

PS: Michael Anissimov and George Dvorsky have covered this topic before.