Thursday, 23 December 2010

The woolly-haired Shuffler: Splendid Insulation

It is cold outside. Then again: there will be a white Christmas, which is largely nice. All that snow led me to choose a wintery scene for my long overdue update of Furahan animals. The update follows the same pattern as previous ones: if I show a new animal, an old one leaves the scene, and that is exactly what has happened. After all, if the Furaha Project is ever to become a book, there should be things in it that are not freely available on the internet.


Click to enlarge; copyright Gert van Dijk

Here is part of the map of Furaha showing the usual covering of snow in Winter for the Northern hemisphere. This is part of the area where the woolly-haired Shuffler lives.

Click to enlarge; copyright Gert van Dijk

You will find the Shuffler on the land page, but here it is again. I could not resist adding some additional information here. At first glance you may wonder where the woolly hairs are, as the animal looks somewhat naked. Well, the hairs are underneath.

There are various ways in which animals can combat heat loss in a cold environment. Behavioural solutions are to stay indoors or sleep through the winter. There are anatomical tricks as well; a good principle is to be as round as possible with as few protruding parts as possible, in order to get a small surface area for a given volume. So, expect small ears, short tails and thick legs for animals in cold climes. A second anatomical trick is to be large, as it is easier for a large animal to conserve heat. There are metabolic and circulatory tricks as well, but a good theme is insulation. Layers and layers of fat wrapped around the more costly parts of the body will help, and as an aside these can store food as well. One of the best insulating materials is air. Fur works because the hairs trap air near the body, preventing the freezing effects of wind to reach warm parts of the body. Fur on Earth works quite well, and various animals have such sophisticated fur designs that they can withstand horrible conditions. Just consider hair that traps sunlight, leading the warming radiation into the body; hairs that are fairly thick but hollow, so they trap even more air; or consider fur made of layers of hairs with different characteristics. But such furs can still get wet, and while even that can be solved -think of polar bears- there is another way to protect against wind chill, and that is the ways humans do it.

Humans? Naked apes? I am talking about clothing. Animal pelts must have been among the first items of clothing, and among women of a certain class, a certain age and a certain cultural background fur coats are still in vogue (I cannot help but think -and sometimes say- that all fur coats are second-hand clothes, and that they invariably looked much better on the first owner). Fur coats work, but modern polar clothes are a miracle of ingenuity. They invariably have fibres to trap air much as hairs in furs do. But there is usually an outer layer of wind-breaking material to stop the trapped air from mingling with the really cold outside air. Animals don't have that, for the simple reason that it would not be easy to enclose large areas of air inside the body (oh well, Furahan tetrapterates do, but that is another story).

Once again, humans solved that particular riddle. Some brilliant Eskimo / Inuit must have realised one day that coats made of fur work even better when you wear the furry side of the pelt against your skin instead of on the outside. That was a stroke of genius, I think, but it is not listed among other great humans inventions such as fire, wheels and gossiping (the probable reason for the evolution of speech). I expect that women who like fur coats do not know this, and suspect they would ignore it anyway.

That Eskimo's idea is behind the fur coat of the Shuffler. Its skin forms folds, and the inside of the fold is covered in woolly hairs, while the outside is devoid of hair. The fold is dead, in fact. This might be as near as the 'Eskimo Invention' as biological evolution can get starting with hair on the outside of a body. The main downside is that investing in large amounts of skin and hair for just one season's worth of protection is costly in metabolic terms, so I played with alternative ideas, such as letting them keep their folds all year. Or perhaps they eat the skin when it falls off, in a rather unappetising manner.

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As you can see, I made some other changes to the web site as well:
I added a new book, on Warren Fahy's 'Fragment'. This is probably the only fake book in the entire New Hades catalogue of fake books that will one day likely be turned into a real book!. It is on the book page, of course.
The list of links has been reworked too, see the 'about' page. Snaiad is gone, but I will put the link back again when Nemo chooses to find a new host. Then again, Nereus is there now...
The illustration on the site's front page has been changed as well; no new items there, but I think it looks better now.

Finally, I have written too many posts on this blog: it keeps me from actually painting new Furahan life forms. Next year, I will probably reduce the frequency of posts to perhaps once every two weeks. We'll see. I do have some ideas for good subjects though. Meanwhile, please consider telling all women with fur coats, except for the ones you really like -the women, not the coats-, that they should wear their coats with the fur on the inside.

Friday, 10 December 2010

Furaha on io9


A few days ago this blog was mentioned on io9, under the heading Mad Science. The article was entitled "An intensive, multi-year study of realistic alien life". There was a definite spike in the number of people who visited my sites afterwards. Welcome new readers!

I was a bit doubtful about the 'Mad Scientist' bit, but what can I say? There is some truth in it; after all, I have been known to work my way through texts on the optical limits of compound eyes, to see whether I could somehow get around the conventional thought that such eyes would have to have a diameter of one meter to obtain a resolution as good as the human one. Is that geeky? I now think that computer science might hold an answer, and if you want me to write a post on that subject, you know what you are...

All right, I admit it: such activities might conceivably be considered geeky by some. In fact, according to Annalee Newitz, who wrote the post in question, my blog is "a treasure trove of biogeekery". Now that is a word to remember. Annalee must be a related soul, as she wrote: "This kind of intense, charmingly maniacal worldbuilding warms the screaming void at the center of my nerdy heart." Well, Annalee, it's nice to be appreciated, and please come again if you need rewarming!

Wednesday, 8 December 2010

An xenobiological conference call

Just a short post this time. If you read this blog, it is a safe bet that you are interested in speculative biology, astrobiology, xenobiology and/or exobiology. I mention all four terms as they are about more or less different things. 'Speculative biology' seems to stand apart from the others; it is about any kind of biology that is not about real living beings, here, there, then or now. It can be about alternative evolution on Earth, such as dinosaurs in the present or about evolution on Earth in the future. Xenobiology, exobiology and astrobiology are restricted to unearthly life. The words 'exobiology' and 'xenobiology' are clearly older, but the newcomer 'astrobiology' seems to have won the day. Personally, I prefer 'exobiology', in part because it evokes 'exotic' and in part because I am linguistically conservative. 'Xenobiology' literally refers to the biology of 'strangers', and so it comes very close, etymologically, to 'alien biology'. 'Astrobiology' is literally about life on stars, and while I am willing to listen to any hypothesis about life, life on or in stars seems unlikely. But I will not be difficult about this; after all, 'astronomy' deals with more than just stars. Essentially xeno-, exo- and astrobiology are all about the same subject.

So, would you wish to go to a xenobiological conference? The full title is '18th International Congress of Xenobiology and Planetary Biology'. The program looks interesting: there will be talks on topics such as 'Xenophages and other new treatments and their impact on Human physiology'. As if Earth viruses and bacteria aren't enough, modified or with their wholly natural charm, you can now get treated with alien organisms. It's completely harmless, really! The introduction of Earth lifeforms in alien ecologies is always good for a controversy, so the talk on 'Introduction and Establishment of Terrestrial Insectoids in Rigel Kentaurus' is bound to draw a large audience. Then again, what do we care about Rigel Kentaurus?

You can read more on the conference on the following website. You will have to be patient though, as the conference will be held on 16-21 September, 2206. Aha; while there are serious conferences on astrobiology, this one is fictitious. The website is beautifully made, and if you ever been to a scientific conference, you will know that this is an excellent parody. It is all there!: there is a social program, a timetable, information about the venue and the hotel, and a list of sponsors. Whoever made this knew what he or she was doing. The author can be found by stripping the web address, and that yields something else altogether.

The website is in Finnish, a language I can recognise but not understand. Luckily, there is a copyright name there: credit to whom it is due, which in this case is Sampsa Rydman. If you work your way through the various options in the menu, you will find some interesting ones. One definitely worth a visit is 'Xenobiologia', proving that some Finnish words are easy. But from then on I would advise you to use Google's translation services. You will find a page with interesting pencil drawings on it, of which I will show two.

Click to enlarge; copyright Sampsa Rydman

This creature is a Löyhkähaahkaja. So what does Google make of the accompanying text? Here it is, without embellishments: "This is a great size (4-5 feet), carnivorous plants attract prey lemullaan intolerable. Although it elääkin entire life rooted in one place, its great tarttumaelimellä a wide freedom of movement. Löyhkähaahkajat spread and multiply rihmajuurakkoaan along."

Well, reading that definitely evokes a 'sense of wonder'. I think that we are looking at a sessile but mobile life form. Other life forms on the page seem to have elements of plants as well as animals, a feature they share with Furahan mixomorphs. The limits of sessile life forms perhaps deserve a post of their own, some day.

Click to enlarge; copyright Sampsa Rydman

And this is a Haaskahyppiäinen. "The kolmeraajaisten hyppiäisten sect belonging to the plains inmate is about 20 cents higher, munimalla growing insect-like vikkeläliikkeinen hajoittajaeläin. They are found largely blue-green leaves and raipparepsukoiden hills and mustaruohotasangoilta."

Right. I thought as much. But look at it: it appears to be a triradial life form, and I have a definite soft spot for radial animals, particularly ones with complex motor skills.

Have a look at the other animals yourself. They are probably more graphically pleasant than biologically plausible, but every once in a while that is admissible. Mind you, if you wish to have a look at the other pages, turn off the translation, or else you will not see the illustrations on the pages. There is a nice planetary map here. I rather liked the images advocating 'robot equality'. I hasten to say that I do not object to treating robots humanely (of course not!) but I hope that does not mean they fall under the heading of 'speculative biology'. Dear me.

I will keep it at this. This is a nice site! I would have liked to have seen more animals, but I guess I will have to wait for the conference...

Sunday, 28 November 2010

Walking without Legs

Pardon? Is walking without legs possible? Well, if you stretch the definition a little...

There are quite a few terrestrial animals on Earth that have no legs; earthworms, legless lizards and particularly snakes come to mind. These are not evolutionary misfits whose leglessness will be their doom any day now. Snakes have been around for some 150 million years, after all. Limblessness in legless lizards seems to have evolved at least 8 times, also suggesting that 'not having a leg to stand on' is not necessarily a bad thing. It is probably a very good thing if your life style requires moving around in confined spaces where legs might hold you back, such as underground, in very dense growth and probably in crevasses between rocks. In fact, you may well wonder whether legless animals might be universal, found on many worlds across the universe.

If so, would all 'serpentiformes' or 'ophimorphs' (take your pick) move in the same way? That is debatable, as there may be one or two possible gaits that do not seem to be in use on Earth. How do animals without legs move on Earth? There are animals whose body length can vary, such as earthworms, but let's only look at those with a fixed body length, such as snakes. You can find more on that using Wikipedia etc., but here is a short summary.

The internet did not let me down in a search for interesting material. In the past I have found that some of my biomechanical ideas to design interesting life forms had also been invented by others designing robots, such as tetropters (radial flyers). In this case it was the other way around, and I came across a mechanical invention that might perhaps be 'biologified'. I found it on the website of the biorobotics laboratory of the Carnegie Mellon School of computer science, where they have lots of interesting material on the design of robotic snakes (there are other robot snake designers, but this site seems to cover all aspects).


Click to enlarge; copyright Gert van Dijk

Click to enlarge; source here

The basic element of robotic and live snakes is a segment (vertebrates are just as segmental as arthropods; the segments are just less apparent form the outside). In the picture above each segment is connected to the next with a universal joint, allowing movement up and down and sideways. The robotic snakes seem to have joints with just one axis of rotation (either up-down or sideways), but these alternate on consecutive joints. There is no movement along the longitudinal axis of the segments. Well, in animals there is almost always a bit of leeway, but not a lot; it's certainly not as if a segment could rotate 10 or 20 degrees along a longitudinal axis. It is tempting to adapt the design to allow more longitudinal rotation, and it would increase the 'alienness' of the design. (We need a word to describe how 'alien' an animal is compared to 'life as we know it'; 'alienosity'?)

Anyway, Earth's snakes can move in various ways. There is the 'rectilinear' mode, in which a bit of skin on the belly of the snake is lifted, moved forward, and put back on the ground again. The next bit of skin does the same thing but slightly out of phase, so you end up with a wave of skin rippling backwards along the belly of the beast. As the ripples push against the immobile earth, the snake moves forward. Think about this: part of the body, while lifted from the ground, swings forwards with respect to the centre of gravity of the body, and when it is on the ground it swings backwards: that is a description of what a leg does, if not what a leg is. A fine distinction, but an interesting one: do you define walking by its functional characteristics, or by the body parts that carry out the function? I tend to prefer the first option, but the consequence would be that snakes walk, and that departs too much from common use of 'walking'.


video

A very interesting snake gait is 'sidewinding'. Here, the snake lifts an entire segment of its body from the ground, moves it forwards, and puts it down again. You get the picture: a walking analogue again. The robotic snake does it too, with waves travelling down the body both in the up and down and sideways directions. In real life it is quite difficult to get a good understanding of how this works using just diagrams, but the videos shown here might help. Sidewinding provides snakes with their fastest way of locomotion: it is the 'running' of the snake world.


video

Now we get to the creative part: a gait snakes do not use. The robot's body is moved into a curve, so it lies in a plane. Now imagine that you change the direction of curvature a bit, so both ends of the animal would be lifted from the ground. That is not going to happen, as the uplifted ends of the body will fall towards the ground. The result is a C-shaped curve that rolls forward, a bit as how you would move a log by rolling it over the ground. I was struck by the creative beauty of this solution.

But before people trot off to design rolling metaserpents for their own worlds, they should think about why Earth's snakes don't do this. Rolling along the longitudinal axis of the body will cause the animals' head to spin quite literally. The poor animal will have difficulty in keeping its bearings. Regular readers may remember that there was a similar problem with cernuation. I wouldn't say this form of locomotion, which the robot designers called 'rolling', is impossible for animals, but the animal better have very sophisticated vestibular and equilibrium systems. Alternatively, or additioanlly, the head could do its own counter rotation, in the same way cernuating animals could temporarily keep their head still. Spinning ballerinas also rotate their head opposite their body to keep it still in space, and they are not alien (perhaps a tiny bit).


video

Here is another example of what 'rolling' can do: the designers have actually been able to make their robot climb a tree! Spectacular, isn't it?


video


And finally, a robot that is not very prominently displayed on their site. They call it the 'skin drive', and about the only information is that it uses its entire skin to move. From looking at the video, it seems to have flexible rubbery skin, and underneath that there must be series of elements that can be stuck out radially and retracted again. I guess that waves of extraction and retraction march backwards across the body, as if you would push successive fingers against a sheet of rubber. If these fingertips find enough traction against the ground, they will stay in place, and the body as a while will be pushed forwards. It is a bit like 'rectilinear' snake movement, but not exactly the same. I wonder where the inventors will take it, or where its evolution will lead to.

Sunday, 14 November 2010

Furaha Swamp Scene II

video

If this scene looks a bit familiar, that is because I posted previous versions of it as well, in November 2009. This version is updated though, and so is still worth viewing, or so I hope. The end is a bit rough: the 'Fish' is visible for a short while only, which is intentional, and so I thought I could get away with a limited amount of detail. There is a better quality version on the site: simply go to the plant page and select the arrox tree.

Click to enlarge; copyright plant image Gert van Dijk

Here is a short 'making of'. The plants were all designed with XFrog, a program aimed wholly at structures that branch and grow, i.e., plants. The various rules and settings can be quite complex, but it allows very good control over the characteristics of any plant you create with it. There are not many good plant editors about. One of the few other candidates is the plant editor inside Vue, but that is unfortunately geared towards changing and mutating existing plants, and does not allow the creation of a plant from scratch. Vue has the advantage that it allows its own plants to move in a breeze, which certainly adds to the liveliness of a scene.
The image above shows one of the flowering plants in the swamp scene, as it looks inside XFrog.

Click to enlarge

The next stage is to produce a suitable environment, for which I use Vue Infinite. Basically you start with a 'terrain', which in this case is the ground with some grooves in it to hold streams. Vue allows the user to define 'ecosystems' as collections of 3D objects that are placed according to rules. For instance, one such system could be limited to high points in the terrain. In this swamp scene the arrox trees only grow on such relatively high ground. The marsh growths, with reeds etc., are limited to medium height zones, while in this case hardly anything grows in the lowest ones. That is on purpose, as they would be obscured by muddy water anyway.
Once the playing filed is ready, the camera is set to fly through the scene, and to produce a ray-traced image 24 times a second, or more. A simple scene lasting 4 seconds may take about 10 hours, so a short film of one minute takes many nights of lonely processing (for the computer, that is; I will be asleep).
And then it is a matter of turning the individual frames into films, for which I use VirtualDub. The resulting clips are much too large to show on the internet so they have to be compressed, at the loss of quality. Adding sound and titles adds to the fun, for which I use Adobe's Premiere (Elements).

And there we are; a Furahan scene that does not actually look that alien. One reason for this is that plants may yield less obvious visual 'alienness' than animals. Regardless , I could not resist putting in an animal at the end. a specimen of a 'Fishes IV' species. I do not yet know how to make the parts of their body move, something that would add greatly to the visual quality of the film. But this is the level of my animation skills at present. I do not think that I will try to become good at it, as there is too little time for that.

Click to enlarge. From left to right, typical examples of species from the Fishes IV, V and VI groups. Copyright Gert van Dijk


But I guess that some of you will want to know more about the various 'Fishes', that are just called that by Furahan people because the word came easily, not because it is biologically correct. In this sense the early Horizonists seem to have gone for the old custom of labelling just about any type of water animal a 'Fish'. 'Crayfish' and 'starfish' come to mind as well. I will not go into the early development of Fishes I, II and II, that follow one another in geological time. Not so for Fishes IV, V and VI, shown above in a rough sketch. Here is a quote from an authoritative source, Nyoroge's "Broad Stokes":

"From this point on hexapod evolution becomes more complex. ‘Fishes III’ gave rise to three new groups, ‘Fishes IV, V and VI’, all of which had three pairs of fins. This has caused a great deal of confusion. There are two schools of thought trying to explain the ‘Fishes III Division’, as the debate has become known. The ‘Hexaphile School’ holds that Fishes IV, V and VI evolved separately from multifinned ancestors, and have three pairs of limbs in common, because three pairs of limbs are innately superior to any other number, without actually explaining in much detail why this should be the case. The ‘Monophyletic School’ contends that all three groups have three pairs simply because they all stem from a single ancestor. This is somewhat surprising in view of other differences between Fishes IV, V and VI, which do not suggest a common ancestry. The ‘Contingency View’, which has been gaining strength lately, holds that there is no innate advantage in any number of limbs, and that all three groups have the same number of limbs by accident. Molecular Cladisticians keep silent about the matter, due to a lack of clear evidence one way or the other."

Tuesday, 2 November 2010

Radial Robots

'Radial robots'; for a title that isn't too bad. I was tempted to add words with 'r' such as 'rampaging' or 'ravaging', but I resisted, as that ran the risk of rather ruining the effect, rendering it ridiculous.

Back to the matter at hand. When I first thought of a radial walking pattern, resulting in Furahan spidrids, I was content to visualise the gait by writing some programmes in Matlab. The results are shown on the Furaha page, and some were featured in the blog as well (here and here). I never imagined I would see really see spidrids walk. Literally, of course, I never will, unless creative bioengineering kits become available quickly, which is unlikely. But walking robots have emerged on the scene since I thought of the spidrids, and among them radial leg designs, as opposed to bilateral symmetry, seem to be quite popular. You can even buy kits to build one yourself. As these designs probably evolved independently, it is interesting to see how parallel these forms of evolution have become: convergent speculation? I therefore surveyed the internet to see whether their anatomy and gaits resembled those of Furahan spidrids. As most of the robots out there seem to be hexapods, I made a quick hexapod version of my originally octapod spidrids (if you need information on spidrids, go to the land section of the Furaha site and select 'walking with...'). A mutation, if you will.


video
Mutated spidrid; copyright Gert van Dijk

And here it is. I cannot call it a spidrid any longer, as that name evoked spiders, and therefore eight legs. Suggestions are welcome. The beasty walks with the simplest possible gait: that is a double tripod gait, in which the six legs are divided into two groups of three. The three legs of a group move in unison, and the two groups are exactly out of phase. Provided that each leg touches the ground longer than it is off it, there will always be at least three lags on the ground (either that or six). This gait, together with sprawling legs, provides excellent stability. As discussed previously, this is useful for very small animals, soupy atmospheres or a very low walking velocity. It also doesn't require subtle neural control, making it suitable for today's rather dumb robots. It is also a bit boring, which is why my spidrids walk with different gaits, but that is another matter.


Click to enlarge; copyright Gert van Dijk

Next, a scheme to show how the joint anatomy works. Spidrids are very simple: there is a joint at the 'hip', in which the entire leg can rotate clockwise or anti-clockwise. The rotation axis is vertical, indicated by a shiny metal axis and a red arrow. All other joints are simple hinges allowing the segments of the leg to be stretched or bent, and the axes are horizontal, indicated by more shiny axes and blue arrows. Now that the basic spidrid anatomy and gait are clear, it is time to see whether the robot creators have evolved completely different approaches, or whether they evolved the same ideas.


video

The first video is of a hexapod robot from this YouTube source. As soon as you see it move you will see that its leg anatomy is exactly that of the spidrid: there is one vertical axis at the hip, and the leg itself only contains horizontal axes. The gait is simple as well, in that the legs move in two sets of three, just like the animation above. I like the clunking sound it makes, as if a whole battalion of Cybermen comes clunking down the street. It does one thing my spidrid animations do not (as yet): it changes gait, in the sense that it moves from a circular rotation to walking again (I could have programmed that, but that is a lot of work...).


video

Here is another one (source here), and this one has a more biological feel to it, in the sense that the movements seem smoother and less mechanical. It does have the same basic anatomy though. Its gaits seem more diverse.


video

Just to show that radial robots are not restricted to six legs, here is an eight-legged one (source here), more reminiscent of the original spidrids. With eight legs there are many ways to move the legs, and the risks of falling are diminished, as it is easier to spread weight-bearing evenly around the centre of gravity.


Click to enlarge; source here

Finally, just a look at this one suggest a radical departure from the norm. It has four legs, but that is not the point, as it still clearly has a radial anatomy. The legs do not seem to be attached in the usual fashion: where they touch the body the joint seems to be a simple hinge with a horizontal axis. In fact, all its joints seem to have horizontal axes. So how does it move its legs in more than one direction? How can it walk if all its legs can do is stretch and shorten? The answer lies in its design: this robot is fundamentally different. It is part of a project in which the robot has an internal representation of its body, so it can learn to move once more after its legs have been damaged. In short, it is a lot more intelligent than its dumb brethren. If you want interesting movements, always add a brain (an insect type of brain will do).


video

And this video shows how it moves: it tilts its body, and that takes the place of (anti)clockwise leg rotations. By varying the tilt of its body the reach of its legs becomes much more varied than with an immobile body. In fact, with the anatomy it has, body tilt is the only way forward (pun intended). What a clever design! I love it.

Does this mean that the 'usual' radial design is flawed? I think not. There are good reasons why this design was invented several times, for robots as well as spidrids: it is simple and allows good mobility. Now, if the robots develop more interesting and sophisticated gaits, we are in business: model spidrids in your own home; what more could you wish for?

Saturday, 23 October 2010

Epona Reconnaissance Flight (Epona V)

The Epona Project was, or perhaps is, probably the first serious attempt to build an fictional biosphere from scratch. There is still a website, definitely worth watching. Admittedly, the project has stopped in the sense that no new life forms have been developed for a long time, nor is that likely to happen. But the website is being added to, and I return to it from time to time. The last blog entry on Epona is to be found here, while another one that shows the same scene as is shown in the film below is right here. This time, I used Vue Infinite (version 7.5) to produce a film of almost one minute duration.

How does this work? Well, first of all, there were the life forms to consider. Steven Hanly had modelled them in the past, and it proved possible to port some of his models into the Vue environment. The 'uther' you see flying in the scene is entirely Stephen's doing. The plants could not be used directly, as present-day computer imagery requires more detail than was available when he first designed the models. They were therefore designed anew, using XFrog for the large leaves of the pagoda trees and for all small plants. The stems of the large pagoda tress were done in Vue Infinite. The trees were assembled in Vue, and Vue's 'ecosystem' feature was used to create a terrain with a stream running through it. Then just imagine that a 5-second fragment of film may need some 34 hours to render.

After that, a bit of sound was added, a process I have hardly any experience with. I hope the result is not too jarring.

Anyway, there we are: perhaps the film is about a robot drone taking a look on an Eponan archipelago, covered by a pagoda forest. There is a larger version on YouTube. The original film on my computer is much better; I wish I knew more about optimising quality while compressing a video...

video

Friday, 8 October 2010

These legs are made for walking (Legs II)

In my last post I played with some concepts about leg design, mostly concerning whether it is better to have sprawling legs or ones that function as pillars. It turned out that there is no answer that is always correct: for large animals pillars help minimise energy expenditure in the form of muscle power, and for small animals sprawling legs provide protection against wind forces, something that gets more consequential the smaller you get. Perhaps wind is also one of the reasons why small arthropods are so good at gripping surfaces tightly: I had thought that that was mainly a neat feature to cling to vertical surfaces or even to land on a ceiling, but perhaps simply keeping put where you are if there is a strong wind weighs in too. What do insects do when there is a real gale out there? Does anyone know?

There are still enough problems to play with. I took the Disneius species that had just evolved last time and decided to take its legs one step further, i.e., I tried to simplify their design some more. The reasoning was that legs largely have to move in the body direction, rendering movements in other directions less important. The result is Disneius mechanicus:

Click to enlarge; copyright Gert van Dijk

And here it is. This has taken the idea to an ultimate form: the joints in its legs rotate purely in forwards and backwards directions. Note that this would not work in real life, as the animal would not be able to turn. In real life you would want to make the feet and at least one joint higher up more adaptable.

The legs are built in a zigzag way, like those of its predecessors. Last time I discussed that avoiding bending ‘moments’ becomes easier the nearer the joints are near the centre of gravity. Mind you, zigzagging legs in which the joints zigzag inside and outside are not necessarily worse than ones that do their zigzagging forwards and backwards. The usual explanation for the anatomy of mammal legs is that ‘vertical’ is better, but just suppose you take one of D. mechanicus’ legs and turn it by 90 degrees. If its foot was directly underneath the hip joint to start with, the rotation will not change that. The joint angles do not change either. All this leads me to conclude that ‘verticality’ in limbs depends more on having straight legs than on the direction the joints zigzag in. Legs that predominantly move forward and backwards have the advantage of allowing simpler joints, and simpler joints may allow less muscle strength to control their position: a good thing. I would expect large animals with highly evolved legs to adopt forwards and backwards bending as well. A bit boring, but that is what you get with universal laws of nature.

Luckily there are enough items left that might make alien animals more alien-looking. As you can see, the fore and aft legs of D. mechanicus are exactly alike. This is not what mammal legs look like. From a mechanical point of view fore and aft leg tend to have different effects, with aft legs providing more propulsive force than front ones. Is that also the reason why mammal knees point forwards and their elbows backwards? It seems as if, starting with a newt, its upper arms were rotated backwards and its thighs forwards to turn it into a mammal with fore-aft moving legs.

Click to enlarge

Here is a picture from this site that explains just that phenomenon. It explains why the bones in the forearm are crossed while those in the leg are not. But that is just one way to look at things. In the same newt-to-mammal trip, a third large movable segment was added to the newt's two. In the front leg the shoulder blade turned into a movable segment, and in the hind leg foot bones were recruited. If you look at the result from a functional point of view, the first large movable segment is the shoulder blade in the front limb and the thigh bone in the hind limb. Both point forwards, and from that the other segments zig backwards and then forwards. That is what D. mechanicus looks like! Based on this functional view, I feel that identical front and hind legs are theoretically quite possible. Prolonged specialisation for braking and weight carrying (front legs) and propulsion (hind legs) might change some aspects, but I see no need to ‘prescribe’ the typical mammal pattern as the only feasible one.

Click to enlarge; copyright Gert van Dijk

So here is a variant (the left one) in which the upper segments starts the zigzag by pointing backwards, not forwards, as in the righthand side one. Can this work? At present I see no reason why not. Perhaps I should do some animation studies to see if any big problems come up. But if there are none, an animal could have front legs that start with a zig and hind legs that start with a zag, or vice versa. They are in the background of the image above, but a closer look follows.

Click to enlarge; copyright Gert van Dijk

And here they are: we could make up interesting leg formulae, like ‘zigzig’for an animal in which both front and hind legs start with a forwards zig (and in which the other segments follow the lead of the first segment). ‘Zagzig’ denotes an animal with a front leg starting with a backwards zag while the hind leg starts forwards. You can think of what a ‘zigzagzig’ means for yourselves.

Click to enlarge; copyright Gert van Dijk

Just for fun here is a herd of the beasties. How many zigzags should there be? I do not know. If there is a proper foot, in which many segments touch the floor, I would expect all of them to bend backwards to promote ‘rolling’ over the ground. If just one segment touches the ground, as in hoofed mammals, I have no idea. But the majority of long segments will likely zigzag.

Click to enlarge; copyright Gert van Dijk

Here is an animal with more zigzags, along with an ancestor. The giraffomorph looks weak to me. There must be an optimum number of segments to achieve good manoeuvrability and/or good speed, but I do not dare speculate on that, or at least not now. I also do not know why the scapula in mammals is not connected by joints to the vertebral column, in contrast to the hind legs. Does it have to do with shock absorption versus propulsion? Perhaps those are good subjects for later posts.

Wednesday, 22 September 2010

Legs to stand on

When I sketch a large alien animal, its legs tend to take on the shape of Earth legs with a life of their own. Depending on their general way of life, the animals' legs look like those of mammals, reptiles or amphibians. When the animals are insect-sized, the legs that take shape on the paper are thin and stick out sideways. Apparently the parts of my brain that are responsible for these patterns are so indoctrinated by life on Earth that it takes an effort not to produce them. I am not alone in this, as a glance at websites such as Speculative Evolution will reveal.

Click to enlarge; from 'Primeval'

The wish to 'alienate' the animals can easily result in trickery, such as inflating the arthropod design to the size of a large mammal, or to give the animal tentacles to walk on. The two images above are from the series 'Primeval', a British television series (I like it, by the way!). The heroes encounter some Silurian animals. As you probably know, there were some impressive arthropods around at the time, but they weren't impressive enough for the makers of this series. A pity, as there are enough ways to tell a good story without being silly. There are various reasons such animals could not be that big, and they could no more cling to the ceiling than you can. Effects of scaling are largely to blame, discussed earlier here and here.

But even if you do take physical constraints into consideration, there are thousands of intriguing questions to ask. For instance, if sprawling legs are a bad idea for large animals, why do small animals have them? Why do mammal legs folded in a zigzag manner, with successive bones pointing in opposite directions? Why shoulder blades? What is the optimal number of leg segments? This post presents some -rambling- thoughts on such questions.

Click to enlarge; copyright Gert van Dijk

Let's start with an animal with insect-like sprawling legs. It's not insect-sized though, but mammal-sized. There are four legs, but that is not the point. There are three segments to each leg, but that is not the point either. The joints are all ball and socket joints providing movement around three axes each; that is a bit much, but I will get back to that.

It does not look comfortable, does it? Neither would you if you had to walk around in a similar position: like doing push-ups all day. The poor beast (Disneius salamandris) will have to spend a lot of energy to keep its body from sagging to the ground. In other words, it takes energy to keep the joints in their current positions. To understand how you can minimise that force requires a bit of knowledge about levers, vectors and torques.

Click to enlarge; copyright Gert van Dijk

Here is a drawing of the body with just one leg. Let's pretend the body and parts of the leg are stuck together, so there is just one joint to consider (where blue and brown meet). Gravity pulls at the mass of the animal at its centre of gravity, with a force marked 'W' (for weight). How much 'turning power' does that result in at the joint? Easy: connect the joint and the centre of gravity with a line of distance d. Now, using vectors, draw the component of W that is at a right angle to line d; that force is what turns the joint (marked with a black arrow 'R'). The longer the arrow for R , the higher the force. How much turning power this exerts at the joint is obtained by multiplying d with F: the turning 'moment' or 'torque'.

Click to enlarge; copyright Gert van Dijk

To make that a bit more intuitive I overlaid a wrench on the graph. The wrench grips the joint, and the part where you would put your hand is at the centre of gravity. To use the wrench you would pull or push on it at a right angle to it, right? That would be the force 'R'. The harder you pull, the larger the torque will be. If you were to use a longer wrench with the same force, you would also get more torque. More force and longer handles; that is about all there is to it. Back to D. salamandris; it will have to exert an equally large torque of its own using muscle forces -not drawn- to stop the joint from moving.

Click to enlarge; copyright Gert van Dijk

Here is the same reasoning worked out for another joint. In all cases the torque, the product of multiplying d with R, calls for lots of muscle power. Avoiding all this energy expenditure calls for minimising the torque. You can make d smaller by getting the joints as close to the centre of gravity as you can. Minimising R also works, and to do that you should make the line d as vertically as possible: get the joints underneath the body. I think that this principle also explains why legs tend to bend in zigzag fashion: it keeps the joints more or less close together and minimises gravity-induced torque. So, poor D. salamandris does it all wrong.

Click to enlarge; copyright Gert van Dijk

But before we let D. Salamandris go extinct, let's have a look at what its sprawling stance means for the anatomy of the joints in its legs. Above you see one leg in a few positions, obtained by rotating it around the axis in the joint connecting it to the body. To get a movement suitable for walking, its foot should move in a straight line from front to aft (in reality the foot would stay put but the body would move forwards; seen from the body it is the foot that moves backwards). Getting the foot on the stripe only requires straitening some of the joints a bit. But ensuring that the foot always points forwards also requires that there is a way to rotate some of the bones around a longitudinal axis. If you start to think about this some more, you will find that having legs stick sideways requires rather complex joints; it may seem easy, but is not.

Click to enlarge; copyright Gert van Dijk

Here is an intermediary stage in standing on one's own legs: this animal has brought its feet in underneath its body, and its legs show a zigzag pattern, but mostly sideways (a final stage will appear in a future post). This does not solve all problems, as you may well ask why insect do walk with their legs sprawling to the sides. After all, if bringing the legs in is so advantageous, why do not all animals do so? There may be two answers to that. Sprawling and having bent legs is not advantageous if gravity is a big problem, as such positions require lots of muscle power. As discussed previously in my posts on scaling, such problems increase very quickly as animals get bigger. Make them smaller, and the added energy expenditure hardly counts any more in the overall budget. There is also an advantage for small animals to have sprawling legs: it helps them from being blown over by the wind.

Click to enlarge; copyright Gert van Dijk

Above is a similar drawing as previously, but now with a horizontal force acting on the animals: wind. Wind forces can cause the animal to topple over, and once again the component of wind force that does that is at a right angle to the line connecting the centre of gravity to the point of rotation: where the feet touch the ground. The animal with the lower centre of gravity and the more sprawling legs is better protected against wind forces: the force R is small and directed upwards, meaning the weight of the animal counteracts it. For the upright animal the story is different: R is directed sideways, is not counteracted by gravity, and the animal only needs to tilt a bit before the centre of gravity is no longer above the feet.

Once again, scaling plays a part: when you are very small, wind forces play a relatively larger role than at our human size. The same works when you supplant air with water: walking under water will be very difficult if the water is streaming at some velocity. So, vertical legs become more advantageous when animal mass increases, and the more so on planets with a strong gravity. Horizontal, sprawling legs are better when being blown over is an issue, and that is more likely to happen when animal mass is very low, when the atmosphere is very syrupy or the wind becomes stronger. Which legs are best when you are an animal on a very high gravity world with gale forces howling through its soupy atmosphere? Difficult to say; perhaps it should have vertical weight-bearing legs as well as lateral struts...

Wednesday, 15 September 2010

Whose alien plants are these ? - bis

'Anonymous' gave the right answer yesterday, when I had already written the first draft of this post. The 'paintings' I showed last week were in reality photographs of glass works of art displayed in natural surroundings. The artist who made them is called Dale Chihuly, whose work I found by traversing the internet looking for alien plants. I rather like the plant shapes he produces: they are very organic looking, and displaying them among real plants provides a pleasing contrast. I thought that showing them in their original form might have made the riddle a bit too easy, which is why I turned them into 'paintings'. I did so with Corel Painter, by the way.

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Above are the three images I had worked over, but now as I found them on Mr Chihuly's website, right here. There are two more I did not work over to give you a further taste of his work. If you wish to see more images of his plant-like creations, you will find many more of them under the column 'temporary' of the 'installations' page; just pick something from the right-hand column and have a look.

After this intermezzo I will be back with a post about legs, discussing things such as why splaying them works for very small animals but not for large ones, and why bones of large animals have a tendency to fold in zigzag fashion.

Thursday, 9 September 2010

Alien plants III: whose plants are these?

While the busiest part of the year for me usually lasts from the middle of August to the middle of July, the present period presents problematic peaks. In short: not enough time.

Therefore I will just continue the alien plants theme by showing a few images of otherworldly plants. So who made them? Do you know?

I warn you that I cheated: the images have been altered to prevent any immediate recognition. I will post the answer in a next post, along with the unaltered images.


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Saturday, 28 August 2010

Adding oddity (alien plants II)

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I don't write often on alien plants, for a simple reason: there seem to be few of them. I wrote about the -real!- plant life on the island Socotra once, shown you Furahan swamps and showed a few images from the British comic strip Dan Dare. My main post on alien plants was devoted to a computer-generated video. The firm that made it produced another one, as I learned from a site called dexigner.com. The images shown here and the video are taken from that site (the video quality on the site is very good). In fact, there I learned that the previous one was called 'Sixes Last'; there are so many copies of it on the Internet that it is not hard to find it, but it is hard to trace its origin. The 'new' one dates from 2006 and is a commercial for an alcoholic drink. I have nothing against that; in fact, C2H5OH plays quite a role in Furahan biochemistry. As 'advertisement' is not exactly a synonym for 'accuracy', do not expect much in the way of plausibility. Then again, the film does not try to be accurate, just intriguing and humorous. It succeeds well, I think. The computer-generated bits seem to be added to real footage, which may explain why the images look very real.

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The second reason to show it is to discuss the problem of how to design odd plants. I have this worrying idea that the basic plant design may not allow much creative freedom, at least not if the definition of plant is not stretched too much. The main ingredients of the definition may be photosynthesis and being sessile, with some -arbitrary- limits in that the plants in question are multicellular and that they are land plants. Photosynthesis needs light, and the best way to get much light is with a large area, i.e. thin shapes. Needles are good but planes are better. Basically a blanket-like shape with roots to pick up minerals and water is all you need. But if the blanket gets too large it may be torn by the wind, and an easy way to avoid that is to distribute wind stress over many small leaves. Growing towards the light avoids being in the shadow of other plants. Branching systems and leaves seem unavoidable, and any alien plant with those will look like an Earth plant.

What can be done is to alter the relative sizes of plants: thick stems, enormous leaves, etc. and giving them odd colours. But there are usually reasons for these proportions as well as for colours, so there is no total freedom here. The simplest way to add oddity may be to add elements of animals: give the plants eyes or mouths. That is what happened in the earlier video as well as in the present one. Eyes are there to tell an organism about its environment: where is the prey, where is the predator, are there good-looking potential mates around, etc. Acquiring information is only useful if you can act on it, and the main limitation here may be the sessile lifestyle. Sessile life forms can certainly be interesting; there are quite a few sessile predators: think of anemones. But there may be a limit on how well developed their sense organs and brains can become. Why have fine eyes and precise grasping arms when your reach remains frustratingly limited? Wouldn't an animal that can do the same things but that can move around be vastly more fit in the evolutionary sense? You may counter that by saying that it may be enough to outperform the dumb and blind types of sessile organisms. In evolutionary biology traits always seem to cost something. The price to pay may be a metabolic one: eyes, muscles and particularly brains are very expensive in terms of energy.

In that sense, high class eyes are jetset organs, reserved for high flyers only. So the puzzle remains how to increase the oddity of alien plants...



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Wednesday, 18 August 2010

Strandbeesten and mantis shrimps

Actually, 'Strandbeesten and stomatopods' might have sounded better, but would be even more incomprehensible, and a blog is supposed to attract readers, not frighten them away. Based on how many readers were attracted by previous posts, I should probably use 'The Future is Wild' and particularly 'Avatar' a lot more often in post titles (and no, Furaha was NOT modelled on Avatar; it is much older). Right; now that I've got that out of the way, back to the strandbeesten.

I discussed Theo Jansen's imaginative mechanical walking machines before on this blog. Literally the word is Dutch for 'beach beasts'. If you do not know about them, read that entry and visit Mr Jansen's site, or just enter 'Theo Jansen' into Google or YouTube. His work came up in this blog because of my interest in animal locomotion. The problem he faced was how you can get a foot to move backwards along a straight line when on the ground, after which it has to be lifted, moved forward and put down again for the next step. For real animals this is not a big problem, as the various segments of a limb are all controlled by a nervous system telling each segment when to do what. As Jansen's devices lack a brain, he needed a purely mechanical system to achieve this sort of motion. In the end he came up with an intricate series of interconnected bars: if you start with a rotary motion of one bar, another bar, ending in a foot, produces a suitable movement. Very clever indeed. Such series of connected bars are called linkages. You can take a good look at his design on this particular site, which shows other linkages as well. When I wrote that post I had never seen a single strandbeest yet, and that has now been rectified. Mr Jansen works not that far from where I live, so it was a matter of time before I could visit one of his demonstrations nearby. This was the case last June, on a very cold and windy day. I will show a few videos I made that day.

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This is a tiny strandbeest, of which there were three. If its sail is perpendicular to the wind direction, the little beast may walk with the wind. I tried pushing it forward as well, and found that it is not in fact that easy to move. While the 'beesten' are quite light, their joints were harder to move than I had expected. There is no lubrication, but the main problem seems to be that the entire shape deforms enough to put shearing forces on the joints. One result of this is that the poor beest tends to topple over. But never mind that, they are an amazing sight.

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Here is a larger one following one of Mr Jansen's assistants.

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And this is the major species present at the occasion. Not only did it have two bodies or trunks, an enormous number of legs, but also two waving membranes at the top that I think were designed to help propel it. These sails were reefed that day however, and the force of the wind on the body was enough to prod the beast onwards. Aren't they wonderful?

In my previous post I wondered how often linkages occurred in biology, but did not look up the matter. I have done a bit of research now, and found that there are quite a few examples. Fish jaws are probably the best-known example (see below). Other structures, such as sheep hocks and human knees are also counted as so-called four-bar linkages. In a four-bar linkage four stiff bars are linked together in a sort of circle by pivots. If you hold one bar still, and move another one, the remaining two must move in a fixed way. What that way is depends on how exactly they are connected. I felt that regarding the human knee as a four-bar linkage is bending the rules a bit, as two of the bars are ligaments rather than stiff bars. If you include connected series of bones as well as ligaments there are lots of linkages in biology; what I was looking for was linkages of bones involved in locomotion, but I have not yet seen any. Presumably a system with more mechanical freedom but with a smart nervous system to control it is simply superior. Still, the other ones are interesting.

Click to enlarge; Wainwright et al, Integr Comp Biol 2005; 45: 256-262

Here is an example of what fishes do with a four-bar linkage. The source is mentioned in the caption, and the colours are my addition. Fish use this kind of mechanism to move their jaws forward and to enlarge the volume in their mouths, sucking in water as well as their prey. There is at least one Furahan animal with a similar arrangement, and those are 'Fishes' too. The jaws of the sawjaw are connected, all four of them, by bars linking them to the neurocranium in a kind of circular linkage.

So where are the mantis shrimps, everyone's favourite Terran alien? When searching for linkage mechanisms I found that there is a four-bar mechanism in their 'raptorial appendages' as well! I like that: somehow you expect animals that not just spear or club their prey but can see depth with just one eye to be special in other respects as well, and mantis shrimps never seem to let us down when it comes to, well, weirdness.

Click to enlarge; Patek et al; Nature 2004; 428: 819

Here is a figure from the journal Nature, no less. The first author, Sheila Patek, has a lab where she studies all kinds of biomechanically interesting things, most notably mantis shrimps. Have a look, as there are quite a few videos and photographs. Under 'multimedia' you will find an inspired lecture she gave on 'TED', where she explains the striking mechanism of stomatopod raptorial appendages. Very interesting. She is not the only one interested in stomatopods either; here is another enthusiast.

So now you know why strandbeesten and stomatopods end up in the same post: they are connected by linkage (I could not resist that one). I guess both also score very highly when it comes to their ability to evoke a sense of wonder.



PS. This is post #100!