The eyes have it!

I guess almost everyone who designs fictive alien life forms want them to look truly 'alien': you want your animal to have something that tells the viewer that this is an original; it should look unearthly and yet as if it ought to look that way. The word 'alienness' is perhaps grammatically correct, but lacks punch; something like 'alienosity' might do the trick...

Frivolity aside, striking a balance between oddity and plausibility is difficult. Darwinian evolution tends towards optimisation, which in reality means the optimal balance between function and cost; economy of design pervades everything in biological evolution. As evolution on Earth has been following that path for quite some time, it is not easy to come up with strikingly different designs that work at least as well as familiar ones.

Doing away with eyes is such a major departure from 'earth standard', increasing alienosity significantly. Imagine sightless animals with otherwordly senses, pinging your innards with sonar or recognising you by the thermal pattern of your warm throat, your cold nose and old hair. Yes, sightlessness fits the bill nicely. But can you do away with eyes? I think not, except under very special circumstances. I will try to discuss why 'the eyes have it', and this will probably need more than one post. The present one will deal with probably the most famous sightless speculative world: Darwin IV by Wayne Douglas Barlowe.

Pronghead from 'Expedition';click to enlarge
Copyright 1990 Wayne Douglas Barlowe

Let me start by stating my admiration for Mr Barlowe's painting skills. The pronghead, show above, works great against the background, and the fact that is half lit works compositionally and also highlights the luminescent spots nicely. I have said it before: I wish I could paint as well. Darwin IV is presented in his book 'Expedition', available from Amazon. A television documentary with computer generated graphics is available as well.

'Eosapien' (fragment from larger painting).
Copyright 1990 Wayne Douglas Barlowe

The picture here shows some ballooning animals floating away in the darkness (they are called 'eosapien', but I suspect that that is a mistake caused by the idea that the 's' in 'sapiens' denotes a plural, but it does not -the plural would be 'sapientes'-). The luminescent spots are well visible on these animals as well as on animals in the distance. Perhaps the latter ought to be less conspicuous, seeing that the eosapiens are predators.

There is an explanation in the beginning of the book 'expedition' explaining why animals there have no eyes. The idea is that the planet was covered in thick fog for very long periods, so that vision as we know it was pretty useless during that time. Animals accordingly developed other senses: apparently there is a pressure-sensitive lateral line system, but not much is known about it. Also stated are the ability to use sonar and infrared, and the latter one is the subject of this post. The infrared sense is apparently located in 'tiny infrared receptor pits'. When the atmosphere cleared up later, these alternate senses were so well developed and entrenched that vision did not have much chance: the first stages of eyes would be poor, and would not convey an appreciable advantage to their owners, so their evolution never got under way. As defences go, this is an ingenious one. I doubt eye evolution would really be held back by superior senses, already present, but that line of thought deserves further thought.

First, let's discuss the heat sense, one of Darwin IV's ways of making sense of the environment. Many of Barlowe's animals have intriguing dots and stripes in glorious colours, glowing in the dark. Now bioluminescence was a brilliant idea with a high alienosity index ( I wish I had thought of that in time). However, it is rather odd for animals to have organs that produce light when there is nothing around to see that light. At first sense offering light to the blind seems a serious mistake, but the text again shows that this critique has been foreseen. It states that these 'biolights' are 'heat-radiating bioluminous spots that appear quite vivid to infrared sensors'. In effect, this means that the production of light is a side effect of the production of heat.

Electromagnetic spectrum from Wikipedia

Here we need to call attention to the electromagnetic spectrum. You may remember that the part humans can see is flanked by ultraviolet on the high frequency side and by infrared on the low frequency side. Now infrared is divided into near infrared and far infrared. Near infrared is in effect another colour, one humans simply cannot see, but which does not represent heat as such (here is a nice photography site explaining it well).

Left, visible light, right near infrared; Click to enlarge
Images from http://dpfwiw.com/ir.htm

There are many images on the internet taken in the near infrared range, 'translated' to activity in the part of the spectrum we can see (a true infrared image is useless, as we wouldn't even see that there was an image!). Many images of woods and trees show that leaves are very bright in the near infrared range, but that does not mean they are warm. They are not; they simply reflect a lot of the near infrared radiation falling on them, coming from the sun (the sun shines brightly in the near infrared range). Remember that a green leaf looks green because it reflects more green light than it does light of other colours. By the way, the images above show that near infrared travels better through haze and fog than visible light does, so having fog as part of the 'anti-eye argument' has its merits.

But do the animals of Darwin IV make use of near infrared? The text states that we are dealing with detection of heat, and that means 'far infrared'. Then again, most objects radiating heat also radiate near infrared radiation, so you could use one for the other. But I will assume true heat detection.

The heat organs on the bodies of Darwin IV's animal also produce visible light. That is not surprising: any fire produces heat as well as light, and often both effects are welcome (come to think of it, a fire that produced heat but not visible light would be pretty dangerous). Light bulbs are only meant to produce light, but are spectacularly inefficient in this respect: most of the power they consume goes into the generation of heat rather than of light. Nature, however, has managed to produce light without heat in the form of bioluminescence. That separation holds on Earth, though. On Darwin IV, you would expect evolution to be faced with the challenge of producing heat as efficiently as possible, meaning without squandering resources such as producing visible light as a side effect. Apparently evolution failed in this respect. This seems rather unlikely, as there must be metabolic ways to produce just heat but not light in a controlled manner. Our own bodies radiate heat but not light, so I do not think that bioluminescence as a by-product of heat production is very convincing.

But the production side of heat signals is not my major concern; that resolves around the reception side: how do Barlowe's animals make sense of the heat signature of other animals? As usual, there are animals on Earth making use of heat detection; the pit viper is probably the most famous one***. This involves making sense of radiation in the far infrared range, something called 'thermography', or writing with heat. I have copied some images from Wikipedia below. There is a good discussion here as well.

Thermography of a cat from Wikipedia

The main point of these images is what they are: images! An image shows you what is where in space. The more pixels you have, the more information the image can carry. An image is made by a camera, and digital cameras have a receptive surface, and the image is focused on that surface by a lens. A cheap camera might have a poor lens, with an unsharp picture, and with a low number of pixels. When better quality is asked for, lenses get better and the number of pixels increases. The above, in a nutshell, is the evolution of the eye (well, not every eye resembles a camera, but many do). Man-made thermographic images show that the radiation of the far infrared basically follows the same principles as visible light does. You can bend rays with a lens, and you can detect them with dedicated sensors. That does not hold for all parts of the electromagnetic spectrum: it would be hard to detect X-rays as they easily pass through tissues, and it is extraordinarily hard to focus them. I would not be surprised at all to find that biological chemicals are better at bending radiation in the visible part of the spectrum than in the far infrared: water bends light. But the premise of Darwin IV was that animals there are able to detect heat, like the pit viper. In such snakes, heat detection still has poor spatial resolution, probably because their heat detecting organs have no lens in them. Suppose the animals of Darwin IV started out a long time in their past with some molecule that responded when subjected to far infrared radiation. Wouldn't evolution drive that organ to become ever better at telling where the radiation was coming from? That development would run exactly parallel to the evolution of the eye. 'Normal' eyes started out that way, and recent evolutionary theory holds that eyes developed many times, in many forms, and extremely quickly too. The ability to detect heat would probably also be subject to the same optimisation process that affected normal vision, so its product would be an eye. Sensitive to other parts of the spectrum than our eyes, but an eye nevertheless...