Basically, we're going to have to taxonomically classify alien life at some point or another. Therefore, we should resolve the issue now by adopting a new classification level higher than kingdom. Name suggestions are welcome- I suggest "realm." This would be used to separate life evolving on different planets or with different biological structures.
-- halffinity, Mar 04 2009

Life, the Universe... http://en.wikipedia...ki/Domain_(biology)
..and everything [loonquawl, Mar 04 2009]

Further alien classification Advent_20Calendar_b2
Much altercation over the classification of fictional alien species in this otherwise pleasant, festive idea. [theleopard, Mar 04 2009]

Psychological Categories as Homologies: Lessons from Ethology http://philsci-arch...s_as_homologies.pdf
...I just thought it was interesting. [zen_tom, Mar 04 2009]

I see your point - but see link. The current Domains Archeae, Bacteria, Eukarya, are classified as "Life" : cellular life, viruses as non-cellular life; So the aliens could simply be fit there: Venusian life, cellular life, non-cellular life; Or, in a sentence: "Oh, this facemelting mold is a venusian lifeform!"
-- loonquawl, Mar 04 2009


Right now, the existing top level classifications (Prokaryota and Eukaryota) assume the presence of DNA and differ in the method of storage and packaging - so I can imagine creating some higher-level classification based on the type of molecule structure used for hereditary storage (DNA, XYZ, ETC) different methodologies could conceivably co-exist on the same planet (couldn't they?) so I think that's a more sound basis for classification.

Of course, that assumes that genetic information is encoded chemically - there might be non-chemical ways of doing the same thing, so there might be a level of classification that covers that.

Then there's the assumption that genetic information is transmitted at all - bang goes another classification.

Did we miss anything else?
-- zen_tom, Mar 04 2009


Why don't we just go by however the aliens are classifying themselves and us? I'm sure we're already on their taxonomic system somehow.
-- phundug, Mar 04 2009


//Did we miss anything else?//

Well there is that small group that fall into *don't* belong to a classification...
-- 4whom, Mar 04 2009


//I'm sure we're already on their taxonomic system somehow.//
And when they actually get here, we'll be on their taxidermic system too.
-- coprocephalous, Mar 04 2009


I've thought about this before. I think there is a finite set of possible organisms as indicated by the fact of convergent evolution, so for example there are ichthyosaurs and dolphins, thylacines and wolves, and in more widely separated taxa, brachiopods and bivalves. Other things could never happen. Cladistics is one approach, and has the advantage of being pro-evolutionary propaganda, which is a good thing in the current climate of anti-rationalism. However, i think it's also possible to explore this set and find subsets within it which are closer to each other in terms of actual physical form, and that's likely to be a lot more useful in classification than looking at the equivalent of the genomes of different organisms. It might even be that form is not the point. For instance, say there are swarms of flying animals out there with emergent sentience. Are they not more our kin than a humanoid which is a non-sentient larval form of a sessile adult?
-- nineteenthly, Mar 04 2009


But that's the fundamental taxonomical question - what is it *for*?

If you are trying fit creatures into a family tree, then "pro-evolutionary propaganda" is kind of the only way to go.

<aside> Are we really in a climate of anti-rationalism? When did that happen?

The alternative usage that you allude to, finding a 'closeness' of essence requires ignoring the biological stuff and focusing on behaviours and creating an ethological taxonomy - which I'm sure someone must have done already (I've a vague idea that it's been discussed here as well)
-- zen_tom, Mar 04 2009


I do not think we should allow any alien species to enter the earth's atmosphere unless and until they furnish themselves with a DNA/RNA based structure permitting ready taxonomical categorisation. I do realise that this would need agreement by all the countries of the world; but as the law would not affect the citizens of the country at all I do not think it would be hard to pass.
-- vincevincevince, Mar 04 2009


I haven't checked the links, but basically some sci-fi writer came up with a sort of taxonomy for civilizations. Civ 0 - Civ III. We are currently living in a Civ 0. I will leave it to the reader to figure out the rest. His system is sufficient in my haggard opinion.
-- daseva, Mar 04 2009


//We are currently living in a Civ 0//
Really, even after the latest US Presidential election?
-- phundug, Mar 04 2009


//I've thought about this before. I think there is a finite set of possible organisms //

Let's stop right there! A finite set of possible organisms! Let's assume, (just here on earth):

1) I agree, it is finite. How large is this finite set? Have we, can we, see it all? And when do we know we have seen it all?

2) I disagree, it is infinite. Is there one other finite set that resembles us enough to proclaim it life? We cannot see all, can we just see one that differentiates itself from us? Or is that possibly an infinite distance from us? And does *not* seeing it mean it is not there?
-- 4whom, Mar 04 2009


//We are currently living in a Civ 0// More exactly, somewhere around .7. It has to do with energy usage- 1 is we harness all the energy of our planet, 2 is the whole solar system, and 3 the whole galaxy. Long way to go...
-- halffinity, Mar 04 2009


//More exactly, somewhere around .7//
must be an interesting scale considering the normal "energy" we use (petrol) is only 25pct efficient as used, we've done nothing with geothermal apart from the odd sauna, and solar-usage mostly consists of letting plants grow in the sunlight (valid but that just puts us on the map at 0)... though come to think of it we're asphyxiating the world by chopping down trees... so wouldn't that put us at a negative score considering that the activities will result in us never achieving even Type I, nevermind Type II status ?
-- FlyingToaster, Mar 04 2009


Yes... Theoretically, a Class I civ would have the power to control storms and be unified on their planet under one banner.
-- halffinity, Mar 04 2009


given global-warming destabilization, weather control may consist of "crap over there instead of here" which is hardly optimal and as for "united under one banner", ummm... nifty, but competition is healthy.
-- FlyingToaster, Mar 04 2009


Pondering Civ I strategies is a halfbaking pastime for most. Civ II strategies are fine, Civ III is ironically uninspiring as far as ideas go.
-- daseva, Mar 04 2009


Civ I 's a bitch: how to use the equivalent of all the (solar) energy hitting the planet without actually fucking over planet and residents.
-- FlyingToaster, Mar 04 2009


I've watched all episodes of Star Trek: TNG multiple times, and I can tell you that the only taxonomy we need is one that identifies forehead type. "Captain, it appears that a band of forehead type G aliens are attacking us! Should we use phasers, or should we just pop their heads with straight pins?"
-- luxlucet, Mar 04 2009


Ha! One of my favourite Ster-Trek things is the explanation that's been built into the back story for why the Klingons had a period (during the Captain Kirk days) where they lacked knobbly foreheads - it's all to do with some horrible genetic mishap, and is one of those things that Klingons prefer not to talk about.
-- zen_tom, Mar 04 2009


[zen_tom], minerals can be classified but they don't evolve. Elements can also be arranged into the periodic table and although there are causal connections between them, they can't be said to evolve in a particular direction. Nevertheless, it is useful to think of them in that way.

An example from known biology: animals on this planet largely depend on gas exchange for respiration. Consequently, they are either small (rotifers), have at least one small dimension (flatworms) or a vascular means of moving gases around (insects with their spiracles, vertebrates and many others with their blood circulatory systems). Organisms which need to live on others for their sustenance tend to have simplified systems in some way, and that applies to male angler fish and to tapeworms. There are implications, so in that way a non-cladistic taxonomy can be useful.

Actually, there are at least two ways of classifying known organisms - genetic relatedness and a less formally organised method based on, for instance, the likes of plankton, nekton and benthic animals, or on commensalism, parasitism, symbiosis and so forth. Maybe this could all fit together.

Also, we're talking about Linnæan classification here, which predates cladistics.

Oh yes, and rationality. Some would say that the West is more rational than it was. What i have in mind is a combination of the likes of fundamentalism, critical theory and "new thought", and all that implies.

[4whom], i think it's finite but extremely large. I can't imagine, for example, that even chordate-like animals are very common, and there are likely to be a whole load of other possibilities not realised on this planet at any time in its history. On the other hand, i think there are probable body plans, for example broadleaved trees/many corals, sea anemones/flowering herbs and oligochætes/snakes/cæcilians.

At the moment, we have no way of telling if we've seen it all, but i'm suggesting that there may be a systematic approach to biology which is nearer mathematics and more theoretical than what we currently have, which i feel is less a single system than chemistry, for example, though perhaps more so than physics because of that whole relativity/quantum thing. That systematic approach could ultimately determine the limits of biological possibility more formally. I think it fails to be infinite in the same way as the set of Platonic polyhedra fails to be infinite. It's possible to conclude that there is only one shape with entirely pentagonal faces without ever seeing one. There are a certain number of regular four-dimensional equivalents to polyhedra which i can't visualise at all, but i do understand the proofs for the limits to the possibilities.

There is an issue of defining life in a sense. There could be complex self-organising systems which don't fall into "life as we know it" at all, for all we know. For instance, at a guess there could be electromagnetic patterns around gas giants which respond to stimuli, use energy in a systematic way, excrete that energy as, maybe, neutral molecules, but never reproduce - they just sit there for billions of years doing what they do until their suns become red giants and destroy them. By our definition, they wouldn't be alive. There might be mineral assemblages on some exotic planet which are Turing-complete for all i know. But what are these things? Yes, i agree, but that means you have to make up your mind what to define as life. That could change, just as the appearance of zero, negative numbers and real numbers changed the definition of numbers, but it doesn't make integral arithmetic invalid.
-- nineteenthly, Mar 04 2009


Apparently, supernovas cause pressure waves that induce star formation in otherwise inert galactic dust. That's kinda like reproduction?
-- daseva, Mar 04 2009


[nineteenthly], I too, favour the finite yet extremely large approach. However, I recently sent you a link on quasicrystals and how they "break" the *previously* allowed lattice symmetries, mathematically the limit to platonic solids stands, but physically we can now create weirder solids that have similar properties to the known platonics, and still stack according to the rules. Mathematical limits are all well and good within mathematics, because we understand our maths so well (we did not think the penrose tiling would apply to lattice crystals). But as seen in the quasicrystals sometimes the maths don't add up, because we don't understand our world so well. This is probably due to our instance on quantisation and all the woes (and benefits) it brings.

Back to the topic. We can use mathematics to predict our world, and we can use mathematics to unequivocally describe the mathematical realm. But we cannot use mathematics to unequivocally describe the world. Not yet, anyway. Therefore I discard your argument that we will find a finite map for life-forms, until we map all life forms, even given finite possibilities. Also, we cannot know if we have mapped all life-forms until we have. Err, did that come out right?
-- 4whom, Mar 04 2009


Oh yes, thanks for that by the way. I watched some of it but i haven't had the time to get all the way through it. It did inspire me to do something on Poincaré tiles with the home ed horde and i did appreciate it. Oh, and the other thought i had about it was, are there any two (or more?) edible compounds which could be used to make quasi-crystals?

As you say, back to the topic. Yes, i can see where you're coming from. Two things about that:

* Could there be a completely abstract biology, like pure mathematics as opposed to applied mathematics? Would it be possible to find out the theory was wrong and yet still find the disproven finite set of possible life forms was somehow beautiful, elegant or maybe applicable to a completely different branch of knowledge, such as, say, nanotech or engineering? There are no animals with wheels, but there are organisms whose whole body rotates, animals with legs and of course everyone's favourite, the hoverduck. Suppose exploring abstract biology turns up a completely new form of propulsion but also doesn't apply to the living world.

* There could also be several very large finite sets not connected to each other. For instance, there could be a set of organic or chemistry-based life, another set of electronic life, another based on plasma and so on, each completely isolated. Given that, there could still be general principles applying to the whole lot.

Having said that, you have persuaded me this could be so.
-- nineteenthly, Mar 04 2009



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