How inevitable was modern human civilization - data

By the way, some birds seem to be particularly intelligent; they've been seen making and using tools.

Primates existed for about 85mln years, Cetaceans for about 48mln years, in all this time nothing got even close to Homo except for Homo. (Evolution of cetaceans Evolution of primates) Of course plenty of other large social animals had an opportunity to develop something like Homo for at least 300mln years before that. (Evolution of Reptiles), or more if we seriously treat possibility of intelligent life in the sea.

So life, animals with nervous system (these are linked, as without nervous system animal complexity is very small), and Homo seem safe.

The case for language and behavioral modernity seems weaker indeed. One obvious argument is that Robin's paper doesn't allow reversal to previous states (die-off of genus Homo - something very likely), so if expected lifespan of Homo genus (due to all ecological changes, and assuming no civilization - the bottleneck event theory suggests it's not too unlikely) was 10mln years, and we expect something like Homo to appear once, then if it took 3mln years, it's 30% of its possible time, what sounds reasonably hard.

Another case for language is that there is no obvious mechanism how it could have evolved, so perhaps our Homo was luckily predisposed for it. And there's no reason why you need Homo for something like language - if chimps or dolphins could be taught grammar, that would be evidence for language being easy - yet it seems that in 600mln years of animals with brains nothing like it have happened.

Language and behavioral modernity are so close that they might be extremely closely related. If they're independent (assuming Homo), we can use expected genus extinction argument.

Or if language turns out to be far older, happening together with Homo (seems unlikely but not impossible), then behavioral modernity needs explanation instead.

Timing as we know it is:

• Life << animals with nervous systems << Homo <= language <= behavioral modernity
• Homo << behavioral modernity

With exact timing of development of language being unknown.

Second Carl's recommendation; Robin's paper is definitely required reading here.

The problem with Cambrian explosion is that it seems to have occurred in way too many separate lineages simultaneously. The most recent common ancestors for animals from Cambrian explosion seems to be go quite far back (that however is another controversial issue, molecular clocks are always controversial), and then suddenly all at once multiple independent lineages undergo period of extremely fast evolution. It's a problem unresolved since 19th century. Wikipedia - Cambrian explosion

In particular, Diamond (I believe, though it's been a while since I read GG&S) argues that wheels have far less obvious utility for vehicles if you don't have pack animals, and therefore don't think in terms of animal-powered transport apart from carrying.

Similarly, it would be more informative to say that Hymenoptera developed a particular pattern of chromosomal inheritance once, and that led to 11 different types of eusocialism.

According to Wikipedia, all of the social hymenopterans are in superfamily Aculea, a monophyletic clade, which seems to lend credence to the "developed only once" hypothesis. (There are non-social aculean insects, but it's possible they used to be social and split off from social species.)

This isn't really true. Only organisms with mitochondria developed multicellularity. Mitochondria are the hard part.

doi: 10.1073/pnas.0702207104:

Multicellularity is widely viewed as a unique attribute of eukaryotes, somehow made possible by the origin of a more complex cellular architecture and, without question, with the assistance of natural selection. However, it is difficult to defend this assertion in any formal way. Complex, multicellularity has only arisen twice, once in animals and once in vascular plants. One might add fungi to the list, although the number of fungal cell types is not large, and there is some question as to whether multicellularity was ancestral to the phylogenetic group that contains animals, fungi, and slime molds. In any event, the probability that two or three origins of multicellularity simply arose by chance within eukaryotes as opposed to prokaryotes is somewhere on the order of 1/4 to 1/2, well below the general standards of statistical validity. Of course, many other eukaryotes are capable of producing a few different cell types, but the same is true for prokaryotes, some of which produce radically different cell morphologies.

I wrote a post about the inevitability of human civilizations declining:

http://onestdv.blogspot.com/2009/08/inevitable-doom-of-human-civilizations.html

There are plenty of ideas how some part of emergence of life might have happened. The problems is that each idea explains just small part of it, they are not all compatible with each other, and many have serious problems. Yes, life emerged, so it must have emerged somehow, but I haven't seen any mechanism that seemed to make it likely.

Where's the bias?

• If something occurred once after long time while it could it seems unlikely.
• If something occurred soon after prerequisites were met it seems likely.
• If something occurred multiple times independently it seems likely.

1 and 3 seem obviously true. There are multiple trials separated either by geography or time, and they have enough failures / successes to make our intuitions right. Anthropic principle doesn't get involved here in any way. If agriculture was invented 5 times independently it couldn't have possibly be the limiting unlikely step.

2 might be luck - something might have been extremely unlikely but just have happened (by anthropic principle). But anthropic principle doesn't really give any reasons why it should have happened quickly. Of course it's extremely naive to consider (like Robin's paper) time as a series of independent trials - maybe it was unlikely as in prerequisites were just in place, and it was either fast or never. That's why I seriously doubt physics-inspired modeling of such events.

I think my reasoning is valid even with anthropic principle. If life wasn't resilient, we should expect by anthropic principle to have no major disasters in the past, not to have survived major disasters.

Voted up for correct use of an observational selection effect a.k.a. anthropic argument.

4) There is a very easy and unavoidable way to destroy the universe (or make it inhospitable) using technology, and any technological civilization will inevitably do so at a certain pretty early point in its history. Therefore, only one technological civilization per universe ever exists, and we should not be surprised to find ourselves to be the first.

5) The Dark Lords of the Matrix are only interested in running one civilization in our particular sim.

Another possible resolution of the Fermi paradox based on the many world interpretation of QM:

Let us assume that advanced civilizations find overwhelming evidence for the many world hypothesis as the true, infallible theory of physics. Additionally, assume that there is a quantum mechanical process that has a huge payoff at a very small probability: the equivalent of a cosmic lottery, where the chances of obliteration are close to 1, the chance of winning is close to zero, but the payoff is HUGE. It is like going into a room, where you win a billion dollar with p=1:1000000 and die a sudden, painless death at p= 999999:1000000. Still, for the many world hypothesis is true, you will experience the winning for sure.

Now imagine that at some point of its existence every very advanced civilization faces the decision to make the leap of face in the many world interpretation: start the machine that obliterates them in almost every branches of the Everett-multiverse, while letting them live on in a few branches with a huge amount of increased resources (energy/ computronium/ whatever) Since they know that their only subjective experience will be of getting the payoff at a negligible risk, they will choose the path of trickling down in some of the much narrower Everett-branches.

However, it would mean for any outsider civilizations are that they simply vanish from their branch of the Universe at a very high probability. Since every advanced civilization would be faced with the above extremely seducing way of gaining cheap resources, the probability that two of them will share the same universe will get infinitesimally small.

There's also some assumption here that civilisations either collpase or conquer the galaxy, but that ignores another possibility - that civilisations might quickly reach a plateau technologically and in terms of size.

The reasons this could be the case is that civilisations must always solve their problems of growth and sustainability long before they have the technology to move beyond their home planet, and once they have done so, there ceases to be any imperative toward off-world expansion, and without ever increasing economies of scale, technological developments taper off.

"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."

By law of conservation of evidence if detecting alien civilization makes them more likely, not detecting them after sustained effort makes them less likely, right?

Counterevidence for 2 - there are extremely few sustained reversals of either life or civilization. Toba bottleneck seems like the most likely near-reversal, and it happened before modern civilization. You would need to postulate extremely high likelihood of collapse if you suggest that emergence is very frequent, and still civilizations aren't around. If only 90% of civilizations collapse (what seems vastly higher proportion than we have any reason to believe), then if civilizations are likely, they should still be plentiful. Hypothesis 2 would only work if emergence is very likely, and then fast extinction is nearly inevitable. After civilization starts spreading widely across star systems extinction seems extremely unlikely.

Counterevidence for 3 - some models suggest that advanced civilizations would have spread extremely quickly across galaxy by geological timescales. That leaves us with:

• Advanced civilizations are numerous but were all created extremely recently, last 0.1% of galaxy's lifetime or so (extremely unlikely to the point that we can ignore it)
• We suck at detection so much that we cannot even detect galaxy-wide civilization (seems unlikely, do you postulate that?)
• These models are really bad, and advanced civilizations tend to be contained to spread extremely slowly (more plausible, these models have no empirical support)
• 3 is false and there are few or no other advanced civilization in the galaxy (what I find most likely), either by not arising in the first place or extinction.

My rating of probabilities is 1 >> 3 >> 2. And yes, I'm aware existential risks are widely believed here - I don't share this belief at all.

Here is another variant:

If civilizations achieve a certain sophistication, they necessarily decipher the purpose of the universe and once they understand its true meaning and that they are just a superfluous side-effect, they simply commit suicide. Here is a blog entry of mine elaborating on this hypothesis:

http://arachnism.blogspot.com/2009/05/spiritual-explanation-to-fermi-paradox.html

No we're not. The data is clearly against this theory.

Coal was barely used until 1800s, early industrial revolution machinery used wood (indirectly solar power), charcoal, and river flow (indirectly solar power) instead. Oil didn't matter much until 1950s.

Amount of solar energy Earth receives annually is 3,850,000 EJ (and if we ever needed more there are ridiculously higher amounts of solar energy available is space). Human primary energy use is 487 EJ, or 0.01% of that. That's of course only because we conveniently don't count solar energy used to grow our food, and heat our planet - otherwise it would be fair to say human civilization uses 99.99% solar power (via photosynthesis, heating, water flow, wind etc.) and 0.01% all the other kinds of energy like fossil fuels, nuclear, geothermal etc.

We know fossil fuels were not necessary for industrial civilization because by the time we started using them we were already had industrial civilization. That's as good a proof as it gets.

History of ferrous metallurgy History of coal mining History of petroleum Solar energy

EDIT: Also, long before railways, river transport, and long distance sea transport were extremely common. If some place was inaccessible by water, canals were built. In fact rivers and canals, not railroads were the main mode of transport during the Industrial Revolution. Water transport requires ridiculously little energy compared to land transport, and requires no fossil fuels - even steam ships can use wood or charcoal. Oil wasn't even essential for transport - even as recently as during WW2 most armies relied on horses for carrying stuff around. Fossil fuels are completely irrelevant for explaining why industrial revolution happened. Transport during the Industrial revolution Horses in World War II