Thursday, 27 May 2010
I was interested right up to the point where camera rotates to reveal that the animal is in fact clinging to a vertical rock surface. Until then I thought that the mouth design was kind of interesting, scraping algae or their equivalents off a flat surface. You could debate on how well it would work, and that would be fun. But the rather large problem is how the animal manages to cling to a vertical rock surface.
It pays to think about the forces needed to keep an object fixed to a vertical surface. The centre of gravity of the object will be some distance away from the wall, producing a lever effect on the contact area. Think of a painting hanging from a nail: the top pulls away from the wall while the bottom presses against it. If you had to fix a heavy object to a wall with only one screw, you would put it in where you have to counteract a pulling force: at the top. The bottom of the contact area will stay against the wall anyway. In short, the top end of the contact area pulls away from the surface and the bottom end presses against it.
This also holds for rock-climbing humans. Feet press against the wall, but fingers pull on it. This is much easier if there are gaps the fingers can be hooked into, as otherwise friction is the only force to stop the body tumbling down. Keeping the body close to the rock minimises how hard the fingers have to pull, so the less secure the grip is, the closer you will want to stay near the surface. The same principles are at work on a woodpecker on a tree trunk: woodpeckers rest their stiff tails against the the bottom contact point, and their claws, the top contact area, dig into the bark and pull on it.
Back to Discovery's 'rocksucking cliffhanger' (as it appears to be nameless I made that name up). The image above was taken from the video, but was rotated to show the animal in its vertical position. It has two legs at the bottom, and at the top the mouth is the obvious device to pull on the rock surface. I must say that this is in itself a rather nice idea. You may argue that such a large mouth would need improbably large flat areas, or that dust, snow or rain water could really make life difficult, but such matters might be worked out.
In the sketch above you see my take on the situation (marked A). The body is held fairly far away from the cliff wall, meaning that there are serious lever effects. A line connects the centre of gravity with the lowest point of contact, where rotating forces will push the feet against the rock. The mouth has to suck rather hard to prevent a fall (blue arrow). But what happens if the animal lets go with its mouth, as in sketch B? Ah, right... No cliffhanger here: it will fall, and I can think of only two ways to stop it doing so. The first is that the new top contact area, the toes, must exert an unbelievably strong sucking ability; that possibility is shown here, but I see no evidence of that, and it is very impractical. The other way would be for the cliffhanger to shift its mouth to a new position extremely quickly, before the body has moved downwards so far that there is no stopping it anymore. The video shows that repositioning the mouth takes about one second. On earth an object will in principle fall 4.9 meters in the first second of a fall! This distance would be less on a low-gravity world, and I do not know how many body-lengths that is, as there is no size indication. Still, it sounds as if the fall would then be unstoppable. You would want the loss of sucking power to last as short as possible: it it would only last for 0.1 second, the animal's centre of gravity would only move downwards by 4.9 cm. The process had better be failsafe though; no second chances here. A much better solution would be to having two or more sucking devices, as their use could then be alternated.
As shown, I do not see the animal working as designed. It's a pity, really. As with Avatar, it would not have been that difficult to get someone to have a critical look and iron out the problems. It's not rocket science, after all. Why do companies as big as Discovery let such matters slip? The only answers seem to be that they take science a lot less seriously than they pretend to do, or that they do not take their audience seriously. I am very much in favour of science popularisation, but fumbling it gives the wrong idea.
Tuesday, 18 May 2010
The planet Furaha occurs in a recent article in the Australian Magazine 'Cosmos'. Seeing how mammals in Australia seem a bit otherwordly, that seems fitting in a way. The issue in question, #32, is devoted to SETI. The Search for ExtraTerrestrial Intelligence has been going on for 50 years now. The word 'intelligence' in SETI always makes me wonder how intelligence should be defined in this context, and I will digress a bit about that subject at the end of this post.
But first, back to the article in question: 'Alien Safari'. It deals with the ways in which matters such as photosynthesis and biomechanics shape animal and plant evolution. It was written by Lewis Dartnell, a British astrobiologist. Long-term readers may remember that Lewis used some Furahan images to help illustrate a talk he gave at the Cheltenham Science Fair in the UK last year.
What you see here is the double spread page starting the article. Yes, that is a Furahan forest, with a greenish hue (that's artistic license). In fact, it is almost the same forest that you saw a few weeks ago in the screensaver post. I am not willing to give away much about the article, as the issue of Cosmos is still for sale, and you should of course all buy it! But I can tell you that there are more Furahan pictures in there, and also that Lewis was kind enough to draw attention to the Furaha website and to yours truly. The 'gracile' neocarnivore that occurs on the 'land' page of the site, and whose head I use for my icon, is there as well. Lewis uses it in the context of hexapod animals to explain the principle of 'centaurism', i.e., the freeing of front limbs for tasks other than a locomotor one. I wonder if this will help spread the use of this word. After coining it, I found out that it seems to be in use in some languages to denote horsemanship, as far as I can tell.
Simply because I could not resist here is another version of that forest, with a somewhat other vegetation. The original is one of the largest renderings I ever did, at 4600 pixels wide. By the way, please do not think that I was the only one contributing illustrations to the article. One illustrator is well known among those who like speculative alien animals, and that is Alex Ries, who contributed his superb 'Shadow of the Sun' painting to the article (and who featured on this blog). Here it is on his own web site.
So, if you all order issue #32 of Cosmos Magazine right now, the editor might ask for more such articles as well as more of my paintings.
Meanwhile, have I got anything against intelligence? Absolutely not; it is just that I wonder how smart a species has to be before it can be counted as intelligent. The most important doubt I have is whether 'smartness' should only focus on the ability to recognise, formulate and understand problems, which seems to be the dictionary approach. I do not care much whether the problems in question concern climate change or more complex questions such as life, the universe and everything. A rather different take would be to reserve 'intelligence' for the additional ability to act on and solve such problems. That might be asking for a lot though, and biological evolution is not a good mechanism to emphasize long-term goals over short-term ones. We have no idea whether or not other sapient species are wiser than we are; apparently Stephen Hawking recently warned that contact with intelligent aliens might harm us, based upon the notion that they might be like us!
Well, there certainly is no intelligent life on Furaha; there was a species once that showed evidence of sapience. However, this species, a predator, went extinct as suitable prey died out on its island habitat; no big mystery as to how that happened...
The main reason for not keeping that species was not cynicism, but simply that I am more interested in biological principles than in sophonts. There is enough to astound and thrill in biology, or in other sciences for that matter. Magazines like Cosmos help popularise science, something I find extremely important. But waxing philosophical means it is time to return to Earth (well, sort of). I just found out that Hawking made his remarks in a Discovery Channel programme that promises some alien animals. I will try to find them, as I am curious how well they follow the sort of evolutionary principles that Lewis discussed in his article, and that I try to explain in this blog. If I find any interesting ones, I will drag them back here and probe them; after all, that is what sophonts seem to like to do to animals from worlds not their own.
Sunday, 9 May 2010
I hardly ever post two days in a row, but this post hasn't got anything new to say about speculative biology, so it does not really count in that respect. It is about the blog itself, which has reached its second birthday. I wished to commemorate it by drawing attention to the fact that several Furaha images accompany an article by Lewis Dartnell (Hi Lewis!) on alien life in the Australian Magazine Cosmos, but my copy hasn't arrived yet. If you are down there, get #32!
Writing a blog is addictive, and I if I did not keep a check on it I would hardly have time to spend on the Furaha project. So where does that stand?
As far as programming maps and texturing planets is concerned, that part is finished, except for designing rivers and lakes that realistically follow terrain contours. But those will be hardly visible anyway, and so have little priority. I have lay-out templates in InDesign so I can show publishers what the book might look like. The one thing that needs attention is paintings. I do not think I need more full ones with background scenery, but rather the kind you would see in a field guide or an encyclopedia. There should be images of hexapod evolutionary descent, of spidrid morphological variability, and of the vast range of Fishes IV, V and VI. As I am a slow painter, I decided to take up digital painting. Most people say that they take to graphics tablets in a day or so, but I am not one of them: I still have trouble linking the scren with my motor programs. While I am slowly winning the struggle with Photoshop, I have now also bought Painter on the advice of a pro (merci Sylvia), a program that feels more natural to me. The gracile neocarnivore's head at the top of this post concerns a design I had already done in oils; I did it again digitally to test the waters. It's not good enough yet, but there's progress.
Thanks to the regular readers and commenters; quite often the comments make me think of another subject for a post.
Finally, I was thinking about changing the name of the blog. When I started I thought it would mostly be about Furaha with some other items thrown in, but that is not what happened; in fact, it is the other way around. Perhaps it should be 'Speculative Biology and Furahan Affairs'; any suggestions?
Saturday, 8 May 2010
But recently I read something very interesting about Earth's cephalopods (squids, octopuses, etc) that shines another light on the ability of cephalopod tentacles to function as legs. By the way, the usual term for octopus tentacles is 'arms', and only the two prey-catching appendages of squids are called 'tentacles'; their other appendages are called arms as well. Because I am looking at their function I will stick to 'tentacles' here. My interest was piqued by the following sentence: "... flexible arms, with no joints as fixed reference points, cannot discriminate between shapes, however elaborate the brain." I found this in a section entitled 'What has limited the evolution of cephalopods?' in a book by Janet Moore on Invertebrates (the book is quite interesting for would-be animal designers).
If cephalopods indeed cannot feel well enough to tell shapes apart, that is bad news for having their tentacles turn into functional legs. In man, the ability to sense where our limbs are enables us to walk in the dark and to recognise objects by manipulating them. I will come back to the importance of this sense, called proprioception, later. First I searched for more data on tactile function in cephalopods. Luckily, there is an excellent summary in Scholarpedia, so everyone can read it.
Click to enlarge; sources through link in text
It turns out that octopuses are quite good at feeling the texture of an object, and you can teach them (using rewards etc.) to tell two objects apart that have the same shape but a different texture. In the graph above octopuses were given two different objects, and they had to learn how to tell the two apart. When the two lines with black and open markings diverge, the octopuses managed to learn the difference, but when the lines do not separate, the octopuses hadn't a clue what the humans wanted them to learn. At the top, the octopuses quickly learned that a cylinder with grooves is not the same as one without them. But if you give them cylinders with the same surface texture, but with a different mass because one has a weight hidden in it, they have no idea. They cannot tell a heavy from a light object. The remaining two graphs were control experiments proving the same thing. Other experiments also showed that octopuses are indeed very bad at recognizing shapes. The most likely explanation is that they cannot judge well where the various parts of their limbs are in relation to other parts.
The Scholarpedia review does not go so far as to state, in contrast to the book, that it is the lack of solid parts that is to blame for this, but that does make sense. Consider our limbs, or those of insects for that matter. Telling where the end of the limb is requires two things: the first are sensors to tell the degree to which all joints are bent, and the second item of knowledge is a table containing the lengths of all segments in-between the joints. In fact, working that out does not require more than fairly simple trigonometry. Can an octopus do the same? The lack of joints makes it more difficult. What it would need is some kind of sensor that can tell where it is in relation to another one in theedimensional space: direction as well as distance. Off the top of my head I cannot think of any biological sensors like that. The point is not whether any exist, but that the octopus doesn't seem to have any! One more reminder that alienness can be found on our doorstep.
Do you actually need propriocepsis? Humans do! There are a few people in whom this sense has been wiped out completely by disease, and these people cannot tell the position of their body and their limbs without looking. Most cannot walk, even though their muscles are fine. There are many more examples showing that the ability to feel where your body is in space in extremely important for human, and I would guess vertebrate, control over posture and movement.
What I find hard to understand is how the octopus moves about without such an option. The clip above shows an octopus disguised as some plants walking over the sea floor (on YouTube here). That is impressive, and there are many more video's showing rather impressive feats of movement. Their control over their tentacles must be organised differently from the way we control movement. Again, they're rather alien.
Can all these problems be reconciled with turning tentacles into walking limbs? Well, yes. After all, the Mark II had evolved a series of incompressible elements with joints in between them purely for mechanical reasons. Those elements of the Mark II are shown on the right in the image above. On the left is its successor, a proper leg with a reduced number of segments. The Mark II set-up is just what is needed to allow propriocepsis like ours to evolve; I am assuming here that it is advantageous to have such a sense. If there is a small sensing error in each limb, having a large number of short segments adds up to more uncertainty about where the limb is than having a smaller number of longer segments. Reducing the number of elements was better mechanically anyway, and may also allow a more sophisticated, or at least more reliable sense of position as well. There are probably advantages in the motor control of movements as well, but I think I will skip that (or reserve it for another post, who knows?).