Did anyone see, "What we still don't know?" (UK TV

[parallaxicality]

The fist episode was called "Are we alone?"

There were a number of interesting points raised, particularly concerning the "Humanoid Aliens" thread over on the "Against the Mainstream" section.

Among the points were

The number of stars with planets now looks to be about ten percent.

terrestrial life's precursors (amino acids, DNA nucleotides) exist in interstellar space, which means alien life would probably have the same chemical blueprint as ours

According to Simon Conway Morris, there are underlying rules to evolution- it "follows an invisible landscape". The camera eye has evolved independently seven times. Squid and vertibrates use the same proteins in their eyes, for the same purposes, even though they must have evolved them independently. Chlorophyll seems to be the optimum solution to the problem of fixing light energy. Other compounds don't do it as well, so life on other worlds would probably evolve it too. Legumes have haemoglobin.

It is therefore likely that any extratrestrial intelligence capable of constructing a technological civilisation would look "eerily like humans"- large head, eyes close to the brain, at least two opposable manipulators.

[eburacum45]

Yeah, right.

Conway Morris is a god of palaeontology, all respect to him: but I am sure he is wrong about humanoids being common among intelligent alien lifeforms (if any).
I think he is wrong about eyes, too. I remember seeing that compound eyes and single-lens eyes did not evolve independently, and that they share some genes in common.

We won't even share the same repertoire of amino acids with an alien biosphere; I do not believe that anything suggests that we will converge towards similar bodyplans on other worlds.

[Moose]

terrestrial life's precursors (amino acids, DNA nucleotides) exist in interstellar space

This is a pretty lofty claim, and one I'm going to have to request a cite for.

[Madcat]

I seem to remember something about amino acids existing in comets.

Ah, here we are. This link has nothing but abstracts I'm afraid. If your lucky, a local university might be able to find a few of the papers in this link:

http://web.mit.edu/afs/athena.mit.edu/user/r/e/redingtn/www/netadv/bioast/clash/orocomets.html

[Madcat]

A slightly more pertinent link:

http://publish.seti.org/general/articles.php?id=65

[Moose]

Cool. It'll give me something to read during the test-run tomorrow.

[Van Rijn]

Sounds like another show about pure speculation.


The number of stars with planets now looks to be about ten percent.


And how would this be determined? We have severe limits in the mass of planets we can currently detect, and there is a lot we don't know about planet formation.


terrestrial life's precursors (amino acids, DNA nucleotides) exist in interstellar space, which means alien life would probably have the same chemical blueprint as ours.


We've found some modestly complex "organic" molecules in space, but so what? There are so many unknowns in the beginnings of life, the processes involved and the environments that life might start that I can't see how this would be evidence for or against anything.


According to Simon Conway Morris, there are underlying rules to evolution- it "follows an invisible landscape". The camera eye has evolved independently seven times. Squid and vertibrates use the same proteins in their eyes, for the same purposes, even though they must have evolved them independently. Chlorophyll seems to be the optimum solution to the problem of fixing light energy. Other compounds don't do it as well, so life on other worlds would probably evolve it too. Legumes have haemoglobin.


I wouldn't even call this interesting speculation. Chlorophyll works well on earth. It wouldn't work so well with a star with a different spectral peak, and just because it is the best choice that was evolved on earth does not indicate that it is the best theoretical choice even here.

As for similarities between species - well, we can still share DNA with bacteria, and use many of the same molecular processes. There are reasons why some features are preserved through evolution - but that doesn't mean that life elsewhere would have started with the same assumptions.

He's making assumptions based on one example.


It is therefore likely that any extratrestrial intelligence capable of constructing a technological civilisation would look "eerily like humans"- large head, eyes close to the brain, at least two opposable manipulators.

Now this is just too much. This is a case of piling assumption upon assumption upon . . .

[archman]

The man in question is correct regarding the evolution of eyes. Its commonly well disseminated amongst the invertebrate zoologist camp. Eyeballs have a gazillion different types and forms with these critters, as opposed to the vertebrates. "Vertebrate-centricity" pervades our general culture, however. I am continually amazed by the lack of invertebrate teaching in american biology classrooms. It's barely improved in college.

As for chlorophyll, I assume he's referring to chlorophyll-a. It's rather more than your average pigment. Without it, the other photosynthetic pigment repertoires don't work. That's why every photosynthesis-capable lifeform possesses it, even those that live in areas where chlorophyll-a's particular absorption spectra aren't too efficient.

Damn. I missed it!! :x :x

[eburacum45]

The man in question is correct regarding the evolution of eyes. Its commonly well disseminated amongst the invertebrate zoologist camp.

Not according to some researchers into molecular phylogeny; the pax-6 eyeless gene is common across a wide spectrum of phyla, and may suggest a common origin.
http://www.ijdb.ehu.es/ijdb2002461/ft65.pdf

As for chlorophyll, I assume he's referring to chlorophyll-a. It's rather more than your average pigment. Without it, the other photosynthetic pigment repertoires don't work. That's why every photosynthesis-capable lifeform possesses it, even those that live in areas where chlorophyll-a's particular absorption spectra aren't too efficient.

Yes; that may be true; but even if all photosynthetic autotrophs throughout the universe use chlorophyll a (which I find unlikely), the many colourful accessory pigments will be more important on worlds with different lighting conditions. Observe the succession of brown, red, and green algae at the seashore as the light intensity drops off with depth; a similar phenomenon will occur on worlds with different light curves.

[Careless]

So are there any animals on earth with brains and eyes that don't have eyes near their brains?

[Sticks]

I'm afraid I fell a sleep during this :oops: #-o

[JohnD]

Sticks - me too! Despite the eminence of the contributors, it came across as a typical Channel 4 cheapo of talking heads with meaningless graphics. Would have been better on radio!

Careless - eyes far from brains? Snails? Hammerhead sharks? Neither disprove the rule though.

John

[archman]

[quote=archman]The man in question is correct regarding the evolution of eyes. Its commonly well disseminated amongst the invertebrate zoologist camp.

Not according to some researchers into molecular phylogeny; the pax-6 eyeless gene is common across a wide spectrum of phyla, and may suggest a common origin.

May is right. Yes, we're familiar with this paper and other works by Gehring. You'll have to understand that zoologists are very cautious with geneticists... they're results tend to be wrong or inappropriately interpreted more often than not. Pax-6 for instance is known to have functions in metazoans exclusive to eyes, or even nervous systems. And other genes exclusive to Pax-6 are known to cause eye development. Monophyletic origin is a fairly new and highly controversial theory. Polyphyletic origin is still accepted until soundly proven otherwise.

Not that we're knocking this paper or geneticists in general, but we wait a while for rigorous corroborative work to be done. There's an odd tendency in the molecular biology world to report only those findings which agree with your hypotheses. Tunnel vision is highly pervasive too.

So to sum up, please don't critique the paleontologist for his comments on eye evolution. He's in the right at this point in time.

[eburacum45]

Oh, no, don't worry; the polyphyletic origin of eyes is almost certainly the case- they are very different in form and functionality from phylum to phylum after all.
Simon Conway Morris is one of my heroes, as is Martin Rees; they are both prepared to think outside the box... I am just a little disappointed to see them apparently constrain evolution on other worlds, and perhaps inadvertently lend support to the pro-humanoid camp.

The invisible landscape that Conway Morris describes certainly exists, it can be seen at work in the development of life on our world; bilateral symmetry, eyes, segmentation, streamlining; but I believe this invisible landscape has a very rich hidden topography, and life on our world has only explored a fraction of it.
When you consider as well the conditions that may exist on other life-bearing worlds, this 'invisible landscape' which evolution explores becomes almost infinite in extent and diversity, and hardly constrains form at all.

[parallaxicality]

One of the comments made by one of the talking heads on that show (whose name I didn't catch- it wasn't Conway Morris) was to the effect of that "hard" science fiction writers feel perfectly justified in constraining the laws of physics and chemistry when applied to other worlds, but leave the laws of biology to wander all over the map.

[ZaphodBeeblebrox]

One of the comments made by one of the talking heads on that show (whose name I didn't catch- it wasn't Conway Morris) was to the effect of that "hard" science fiction writers feel perfectly justified in constraining the laws of physics and chemistry when applied to other worlds, but leave the laws of biology to wander all over the map.

That's because there Are NO Hard and Fast Laws to Biology ...

We're Still feeling Our Way, through it.

[Ilya]

So are there any animals on earth with brains and eyes that don't have eyes near their brains?

Crabs. A crab's nerve center is roughly in the center of its body. However, crabs are a relatively recent group, only about 30 million years old, and they evolved from lobsters/crayfish, whose brains are in the head. (Technically, crab's body is ALL head -- it's a ballooned out lobster's thorax. And lobster's tail -- which is really not a tail but abdomen, -- is still present in crabs, but very small and usually tucked in.)

[archman]

So are there any animals on earth with brains and eyes that don't have eyes near their brains?

Crabs. A crab's nerve center is roughly in the center of its body. However, crabs are a relatively recent group, only about 30 million years old, and they evolved from lobsters/crayfish, whose brains are in the head. (Technically, crab's body is ALL head -- it's a ballooned out lobster's thorax. And lobster's tail -- which is really not a tail but abdomen, -- is still present in crabs, but very small and usually tucked in.)

Well... that's sort of correct. Both your brachyuran and anomuran crab lines have reduced abdominal segments, but they possess fairly advanced brains in the front of their body. It's just that the "front" of their body happens to look to us as the top center. The invertebrate zoologists (me) still refer to it as the anterior and cephalic regions. If you want to get REALLY anal, the stellate ganglia comprising their brain is spaced slightly forward in the carapace, not too far behind the eyes.

There are oodles of invertebrates that possess photoreceptors in bizarre parts of the body. Your humble horseshoe crab for instance has at least FIVE eyes in different areas of the carapace, and there are light/dark receptors in the TAIL. With cubozoan jellyfish, there isn't even a central nervous system (much less a brain), but the thing has four eyes. Everyones' favorite lately are the alvinocarid shrimps found around hydrothermal vents. Some species possess two photosensitive "bars" on their BACK. They've been discovered to have outstanding detection ability of extremely dim light, and even the infrared "glow" of high temperature fluid flows. Our submarine lights blind 'em, ha ha.

But despite all these crazy wacked places, IMAGE FORMING eyes seem overwhelmingly confined to the cephalic areas (head). I can't think of an example otherwise, not off the top of my head anyways.

[JohnD]

All,
Should we be surprised that eyes are close to the brain? Evolution has minimised the distance.
We are all familiar with the effects of fast and slow nerve conduction - stub your toe and sensation of the blow is (almost) instant, but perception of the pain follows on an appreciably large fraction of a second later. Nerve conduction is slow!
Vision is such a complex sense, requiring processing in the retina even before it gets to the higher centres. If the delay involved in transmitting the image from a distant eye were added, then it would become even more difficult to predict the movement of prey or the swing of a tennis ball!
John

[Paul Beardsley]

Interesting discussion, I wish I'd remembered to watch or record the programme instead of playing Prince of Persia 2.

A few thoughts...

The 10% of stars have planets thing is presumably a minimum? We know some stars have giant planets; we suppose they probably have smaller planets too, and other stars might well have undetectable planets.

As several have remarked, it's speculation, but at least it's speculation with some grounding. If we venture out to other worlds that resemble Earth, we can't expect to find people like us walking on the grass, but we shouldn't be too surprised if we do. (As a science fiction writer I find this comforting.)

Hard SF writers are strict with physics but lax with biology... Probably true. Can anyone name three SF writers who really, really know their biology? (There's Brian Stableford. And Greg Bear. And... did I mention Brian Stableford?)

[eburacum45]

Brian Stableford has certainly come up with some good stuff, space adapted people and intelligent chimps; David Brin is not bad in that respect either. I have been very impressed with Greg Bear's fictional biologies- particularly those with entire ecologies dependent on horizontal gene transfer.

The natural history of our own planet is much more complex than most people realise; microbes seem to be far more diverse in their genetic makeup than all the macroscopic organisms combined, and life on our planet can be divided into the domains archaea, eubacteria and eukaryotes, with plants and animals being just two of seven (or more (http://www.geosociety.org/pubs/gsatoday/grgsat/0007-2.htm)) kingdoms of life;

if evolution had played out differently, an entirely different set of eukaryotic kingdoms could have arisen to take the place of animalia and plantae.
For instance the thermotogales (http://www.palaeos.com/Kingdoms/Prokaryotes/Thermotogales.htm) with their interesting strategy of gene 'co-option' could have continued and developed that that strategy if they were to develop into a new kingdom of plant-like green eukaryotes with a predilection for horizontal transfer and piracy of genetic material.
The result could have been an ecology like that of my imaginary planet Kemmerer (http://www.orionsarm.com/worlds/Kemmerer.html)...

[Van Rijn]

All, we are all familiar with the effects of fast and slow nerve conduction - stub your toe and sensation of the blow is (almost) instant, but perception of the pain follows on an appreciably large fraction of a second later. Nerve conduction is slow!


Certainly, and that is a good argument why things work that way - with earth biology. But nerve signal communication is incredibly slow compared to what is possible in electronics. Why couldn't there be a biological coax/optical/etc. cable?


As several have remarked, it's speculation, but at least it's speculation with some grounding. If we venture out to other worlds that resemble Earth, we can't expect to find people like us walking on the grass, but we shouldn't be too surprised if we do. (As a science fiction writer I find this comforting.)

I would find it absolutely astonishing. This is so far beyond the basic question "Is there ET life?" and we know so little, I can't see it being anything other than pure speculation. In our exploration of space, even with relatively simple issues, we constantly find we have made wrong assumptions. Biology is very complex - and we would be talking about an alien biology that need not have followed the same path as earth life. The physical bounderies of what is possible are very large.

[archman]

All,
Should we be surprised that eyes are close to the brain? Evolution has minimised the distance.
We are all familiar with the effects of fast and slow nerve conduction - stub your toe and sensation of the blow is (almost) instant, but perception of the pain follows on an appreciably large fraction of a second later. Nerve conduction is slow!
Vision is such a complex sense, requiring processing in the retina even before it gets to the higher centres. If the delay involved in transmitting the image from a distant eye were added, then it would become even more difficult to predict the movement of prey or the swing of a tennis ball!
John
Electrochemical nerve impulse are quick! The "lag" occurs in more complex processing of sensory information. For behaviors that don't require a trip to the brain to "mull over" (i.e. reflexes), the ganglia in the mammalian spinal column take the signal, and immediately route a preconditioned response to the appropriate area.

Just in humans alone, there are five general fiber types, with six groupings for transmission speeds (ranging from 1-80 meters/second).

Certain invertebrates carry "giant neurons" not found in vertebrates. These things are visible to the naked eye, and used a lot in research. As transmission speed is positively related to fiber diameter, these suckers use the "brute force" approach. Escape responses are typically cued into these things, and man are they fast!

Regarding keeping your eyes and other complex sensors near your brain, well there are various behavioral explanations of course. A much simpler explanation is cost of "infrastructure". Nerves are one of the most energetically expensive cells in living organisms. That's why animals that don't need a complex nervous system never evolve one, even accidentally. If they evolve into a "more boring" form or one that can't energetically maintain their nervous system, it's rapidly evolved into a degenerate state.

Keeping expensive nerves close to the processing ganglia saves on metabolic upkeep.

[JohnD]

Archman,
Thanks for taking up cudgels!
Quick or slow are relative. Yes, some nerves can conduct at 80m/s but they are heavily 'insulated' with Schwann cells and achieve fast transmission by saltatory conduction. So they are much thicker than slower fibres and Giant fibres are an extreme example. I honestly don't know how many nerve fibres there are in the optic nerve of a developed animal, but I wonder how thick it would need to be if it was to a remote eye.

You are right of course about "infrastructure", but some animals have found an advantage, hammerhead sharks for instance. It is of interest that vetry different animals with binocular vision all have similar proportions to the face if you look at them from the front, for instance primates, lemurs, cats and dogs, owls. Is this 'infrastructure" or evolution?

Van Rijn,
I think you have to explain how a metallic conductor could be formed and exist in a biological context, or a new biology. In ours, water contaminated with any salt is pretty corrosive! Gold wires?
Optical fibre is a possibility, if you are a sponge - see http://www.electronicsnews.com.au/articles/2a/0c01972a.asp
Sponges and corals possess means of manipulating silica that 'higher' animals do not. If this were to develop into a nervous system - it hasn't so far - then who knows?

John

[eburacum45]

...water contaminated with any salt is pretty corrosive! Gold wires?

of course!
An excellent idea: thank you!
My extremely nonhumanoid alien species the Mucoids (http://www.orionsarm.com/clades/Mucoid_Empire.html), a collective organism made of thousands of vermiformes connected by threadfilled mucus, could excrete gold wires in their tunnel complexes and build up increasingly complex processing networks. (I was thinking zinc or copper but of course they would corrode; they can still use them to generate electricity perhaps.)



Whole phyla could arise from advanced self-replicating technology left behind by long dead intelligent civilisations; not really unassisted evolution, but I would certainly not be surprised to find whole postintelligent biologies out there; they may even outnumber naturally evolved biospheres.
here's one (http://www.orionsarm.com/worlds/Stanislaw.html)

[Van Rijn]

Van Rijn,
I think you have to explain how a metallic conductor could be formed and exist in a biological context, or a new biology. In ours, water contaminated with any salt is pretty corrosive! Gold wires?
Optical fibre is a possibility
John

Even in our biology there are many processes or materials that have to be insulated or protected in one fashion or another. I don't see any reason you couldn't have insulated metallic pathways where "insulating" cells could repair and maintain the metallic path. But also, salty water - especially with the right salts - can be a pretty decent conductor. Conducting polymers are another possibility. Ultimately, though, this is making assumptions based on our biology.

The switching and communication speed in computers is radically faster than in earth biological systems. So, in principle, it is physically possible to far exceed the limits of our biology.

The only point I'm trying to make is: Don't make assumptions, don't be a chauvinistic Terran :) ... based on assumptions about Earth biology. Aside from theoretical physical limits (available energy, speed of light and so forth) I don't think there is really much we can be sure of.

[JohnD]

Van Rijn,
I am all in favour of speculation about what may be possible, but it should be based on what we know IS possible. Otherwise you fall into the,"With one bound he was free" school of plot-problem solving. Moreover, good SF is written with as few assumptions as possible - for example Larry Niven's teleportation stories. Read "Flash crowd" if you haven't already.

If you assume a wholly different biology - silicon based? Plasma based? - then for a good story it should be based on the minimum necessary 'what-ifs'. Then work out the limitations as well as the possibilities of your speculative world. A good example is Robert Forward's two books (the second is "StarQuake") on a society of beings that live on a neutron star. I have to say that while his expertise in physics allowed him to go into fascinating detail about what his beings' lives would be like, what they could acheive and aspire to, his ideas on their biology were a bit unconvincing, shall we say, although he tried to bring in reproduction and rejuvenation.

Also, remember that terrestrial nerves conduct in a wholly different way to a metallic wire conductor. A signal in the latter occurs when a voltage causes a current of electrons all the way along the conductor. In a nerve, the initial impulse triggers the resting potential to discharge in the end organ, which triggers the adjacent piece of nerve cell wall (axon) to trigger and so on. The impulse is carried along the nerve by a wave of electrical discharge. Moreover, this process is an active, biological one, not passive like the wire. The impulse may be stopped at any point by interference with the biology - hypoxia, electrolyte disturbance or a local anaesthetic.

I hope I'm criticising your ideas constructively. Speculate away!

JOhn

[Van Rijn]

Van Rijn,
I am all in favour of speculation about what may be possible, but it should be based on what we know IS possible. Otherwise you fall into the,"With one bound he was free" school of plot-problem solving. Moreover, good SF is written with as few assumptions as possible - for example Larry Niven's teleportation stories. Read "Flash crowd" if you haven't already.


I have no argument with this (and, btw, I've read almost everything Larry Niven has written, including the near future jump booth stories). My only issue has been about making assumptions about ET life based on what we think we know about earth life. Here (from the show this thread was started to discuss) is the assumption I found extremely troubling:

It is therefore likely that any extratrestrial intelligence capable of constructing a technological civilisation would look "eerily like humans"- large head, eyes close to the brain, at least two opposable manipulators.


This makes a mind boggling number of assumptions. As part of a clearly fictional story, this would be fine, but it shouldn't be suggested that this is more than weak speculation. Of course, physical limits must be assumed. There must be sufficient energy available for life to function, signals can't travel faster than light, there are limits to the strength of structural materials, and so on. But earth life has only explored a small subsection of what is physically possible.


I hope I'm criticising your ideas constructively. Speculate away!

JOhn

Thanks, but understand that I was only offering alternative possibilities to assumptions based on earth biology. To be clear:

I do not assume there is ET life. I do not assume there is not ET life. Beyond basic physical limits, I do not make any assumptions on what it would be like, if it did turn up. Complex life is so far beyond this basic issue that I don't think there is much that can be usefully said about it at this point in time.

[JohnD]

All,
To return to the original theme, I've just been watching the next episode of this prog. In fact it's still going on and I'm so fed up with it, I cme out here to post.

The verbal content I have no argument with, Prof. Rees is an excellent teacher and speaker but the director clearly considers that his viewers have the attention span of a goldfish. I tried taking a note of the changes of visual content, that went something like this:
Prof.Rees (MR) talking to camera about the concept of atoms/ a blinking eye/ out of focus light bulbs (OOB)/ MR walking in a garden (MRW)/ MR to camera/ MRW/ a sunset/ Starry sky/ a scientist (S), talking to camera about spectral analysis from halfway up a spiral staircase/ Starry sky/ S/ Moon set/ OOB/ Sunspots/ Sun and clouds/ a blurry spectrum/ S/ Sun through palm trees/
etc, etc, etc...... my writing hand got tired.

That sequence took about two minutes. None of the images were relevant except through verbal association. For instance the spectral analysis was said to identify elements, but no mention of how, just a pretty spectrum, not even with absorbtion lines. Worse, many iof the images were repeated over the next five minutes or so - we got the sunspots, the out of focus bulbs and the starry sky again and again.

This is science "lite", chewing gum for the eyes, wasting the enormous potential of TV. Worse, it is science cheap, an apparently prestigious science programme that C4 can point to as part of their public service, that cost peanuts to make.

Join me; write to C4 and tell them that it just isn't good enough. The opinion of those of you who are scientists and teachers will have even more weight. If a penurious public TV channel in the US takes it, please tell them too.

John

[eburacum45]

Yes; and there seemed to be an awful lot of interviews going on in corridors and stairways;
don't any of these people have offices?

I could have made better images myself in some cases...

[John Dlugosz]

If you assume a wholly different biology - silicon based? Plasma based? - then for a good story it should be based on the minimum necessary 'what-ifs'. Then work out the limitations as well as the possibilities of your speculative world. A good example is Robert Forward's two books (the second is "StarQuake") on a society of beings that live on a neutron star. I have to say that while his expertise in physics allowed him to go into fascinating detail about what his beings' lives would be like, what they could acheive and aspire to, his ideas on their biology were a bit unconvincing, shall we say, although he tried to bring in reproduction and rejuvenation.

Also, remember that terrestrial nerves conduct in a wholly different way to a metallic wire conductor. A signal in the latter occurs when a voltage causes a current of electrons all the way along the conductor. In a nerve, the initial impulse triggers the resting potential to discharge in the end organ, which triggers the adjacent piece of nerve cell wall (axon) to trigger and so on. The impulse is carried along the nerve by a wave of electrical discharge. Moreover, this process is an active, biological one, not passive like the wire. The impulse may be stopped at any point by interference with the biology - hypoxia, electrolyte disturbance or a local anaesthetic.JOhn

In another of Forward's novels, he has huge creatures on Saturn with the eye on a stalk quite distant from the brain. It had superconductors for the associated nerves.

[mid]

This week's episode was really good, I thought. Even if the whole "oops, we need Dark Matter to make everything contract together more", "oops, now we need Dark Energy to make it expand again" thing still rather gives me a headache, and they didn't really touch on it as much as I'd like them to.