Brian Cox: the Wonders of Life. The evolution of the senses

In the most recent instalment of the BBC series The Wonders of Life, presented by Brian Cox, Professor Cox explained that different creatures gather information about the world in very different ways, using different senses. He explained how,as a result, different creatures have very different ideas of what the world around them is all about.
To illustrate this concept Professor Cox gave the example of a particular type of fish that lived in very muddy water. Because the water was so muddy, vision wasn’t of much use to this particular fish. As a result, rather than using vision as its primary sense as we do, the fish used taste. For this purpose the fish had ‘taste buds’ scattered over its entire body with which it sensed the chemical composition of the water in which it swam.
It was an interesting enough fish to be sure, but the ability to sense the world through taste by using taste buds that aren’t purely confined to the tongue isn’t, to me, alien enough to make the fish the ‘go to’ creature for illustrating sensory unfamiliarity. After all, we’re all familiar with taste, and taste is very similar to smell. Not exactly insignificant or unfamiliar senses. We spend a fair amount of time smelling the world in a rather low key way. (And smell is a sense that we can easily make sound more mysterious than it is if we turn our minds to it. We can, for instance, say that we can ‘look into history’ using smell – by sensing things that aren’t there anymore. Sounds impressive, but this is just an over-inflated way of saying that you can smell the fact that yesterday someone burnt the sausages.)

For me the ‘go to’ creature when it comes to sensing the world differently to us is the bat. Because the bat uses sonar or echolocation – a sense that we totally lack (unless you insist that the fact that we can detect mountains by their echos when we shout from the top of one counts as such a sense).

We can’t really imagine what it’s like to have echolocation, but here’s a piece of writing about what it must be like to be a bat trying to understand our sense of vision.

How a blind bat with no concept of vision would be puzzled by the way that humans act

Imagine how a blind (though highly intelligent) bat would try to make sense of our sense of vision.
Bats are not actually blind, contrary to the saying ‘blind as a bat’, But for the sake of this example let’s imagine a species of bat that is indeed totally sightless.
Being a bat, it posesses that uniquely chiropteran sense, echolocation.
With echolocation, or sonar, the bat emits a high pitched noise and then detects the sound waves that are bounced back from objects in the form of an echo. You would think that the resulting ‘sound image’ would be quite crude, a little like the sonar images that are picked up by submarines, but in fact there’s no reason why it shouldn’t be quite detailed – after all, bats can catch flying insects, which is more than we can do.

Given the right circuitry, the brain can just as easily construct an ‘image’ of the world based on information from sound waves as it can construct one from light waves. The main difference with a sonar image when compared to a light image would be that it would have no colour differences in it. Using sonar, a white coffee pot would ‘look’ exactly the same as a black coffee pot or a red or a yellow coffee pot, as the sound waves would echo off them all in the same way. Similarly, shadows would be undetectable. The image would probably contain only one ‘colour’ as we know it – that being the colour that the bat’s brain creates to give form to the objects that are in the image. In a sonar image the world may possibly appear as though everything in it had been sprayed with a single colour of paint.

So, a blind bat can easily use sonar to navigate the world. It would have trouble telling the difference between green unripe fruit and red ripe fruit, but then bats that use sonar don’t eat fruit, only insects, so that’s not a problem (Fruit bats on the other hand, which do eat fruit, have excellent eyesight and no sonar).
The fact that sonar only indicates the form of objects and doesn’t differentiate between different colours has some intriguing consequences.

Imagine that you had a pet blind bat, that travelled around with you by hanging upsidedown from a special perch on your shoulder.
The bat, observing your actions from your shoulder as you went about your everyday business, would be perplexed by some of your behaviour, to put it mildly.
The bat would observe you sitting down while you were reading for example. It would watch you as you stared intently at the pages that you were reading, whether they were on a paper page or on the screen of a digital device. The bat would notice you studying what you were looking at in detail, your eyes scanning from side to side starting at the top of the page or screen and slowly moving down. The bat would not have a clue what you were doing. The bat, which due to its sonar-based vision only sees surfaces and not colours, would see you staring at a perfectly featureless sheet of paper or screen – neither writing nor photographs on the page or screen would register for the bat. The bat would notice however that strangely, once you’d finished this inexplicable activity, you would have mysteriously acquired new knowledge about something – perhaps about the unsavoury lifestyle of a particular celebrity, the score of the latest football match or the state of the economy in China.
Imagine that after you had acquired this important information you decided to go and look out of the window for a while, to mull things over.
Again the bat would be perplexed as you stood in front of a large area of panelling that for some reason was recessed into the wall of the room. For the bat, its sonar signals would be hitting the glass in the window and bouncing straight back, just as they did from any other surface in the room. In ‘sonar vision’ the window would be as opaque as the walls around it (and exactly the same colour, like everything else).
Imagine that while you were looking out of the window you saw a friend walking towards your house, obviously planning to drop round. You’d maybe go to the door and open it in advance of the friend reaching it. The bat would be astounded. It would wonder how you knew that a person was walking towards your door (The bat hadn’t heard your friend approaching, due to the excellent sound insulation of your house, and the bat’s hearing is better than yours, so the bat knows that you certainly hadn’t heard the person approaching). Perhaps you were telepathic – or maybe you had some strange sense that allowed you to literally see through that particular framed part of your house’s solid walls that you were staring at. Surely not!

To the bat your ability to suck information from the blank pages of a book or screen and your facility at knowing what’s on the other side of a solid wall would seem nothing short of miraculous.

The bat would probably be very intrigued by your strange superpowers, but it would be equally intrigued by the fact that in certain unusual circumstances, rather than possessing uncanny sensory abilities these abilities would seem to dessert you altogether and you’d seem to lose almost all ability to sense what was going on around you at all.
Imagine this.
The bat would have been perplexed by your behaviour late one evening when you were going about your business in your home as usual, when suddenly, for no apparent reason, you stopped in the middle of what you were doing – walking into the kitchen to make a cup of coffee perhaps – and started acting as though you had lost all awareness of the positions of the objects around you. The bat would wonder why, suddenly, you had started groping with your hands in order to find your way about, moving hesitantly and clumbsily, holding onto objects as if to check their positions by the use of your sense of touch alone.
The bat would be perplexed by the fact that, strangely, not only were you doing this, but any other people in the house were doing exactly the same thing. And had started to do so at exactly the same moment. The only clues as to what on earth may be happening were the various exclamations being uttered by people in the house. Exclamations along the lines of ‘Oh no – a power failure!’ and ‘Where’s the flashlight?’
The bat, being totally oblivious to light and dark, would be unaware of the visual restrictions of nighttime that apply to humans and other creatures that use vision as their main means of navigating the world.
The bat would then be further perplexed when you fumbled in a drawer and retrieved a plastic object with a switch on the side: an object that you refered to as ‘the flashlight’ or ‘the torch’ depending on your country of residence. Interestingly, when you held this contraption out in front of you, you seemed to regain a limited degree of your powers of navigation, though mainly in the direction in which you pointed the object.

Further bafflement would overwhelm the bat when one of the people in your house suggested ‘Because there’s a power cut and it’s so dark, let’s go outside and look at the sky.’
Following the person with ‘the torch’ or ‘the flashlight’ out into the garden the people of the house would then stand and crane their necks to gaze upwards.
‘What a beautiful crescent moon!’
‘There’s Orion!’
‘Look at all of those stars!’
Despite the people’s obvious inability to be able to notice where they were walking without the use of the mysterious torch or flashlight device, everyone was now peering at the sky and noticing things that weren’t there.
The bat would think “What is this ‘moon’ of which they talk? What is this Orion? What are stars?”
To the bat, which detects objects solely by the presence of an echo in its sonar, the moon and the stars are unknowable. Whenever the bat sends sound signals upwards into the sky they are never returned. There is no echo from the moon or the stars. The signals simply fade away as they approach the vacuum of space. To the bat the sky is nothing but a void into which sonic pulses disappear forever. There’s nothing there.
But people, with their inexplicable senses, seem to know otherwise.

So it is that a blind bat can’t be aware that there is a whole universe of stars and planets out there. It can’t know this simply because of a consequence of the manner in which its sense of location works, because sound doesn’t travel in a vacuum.
It’s pure luck that because of the way that our sense of vision operates, when we look up at the sky we can see the moon and the stars and the planets spread out before us. It’s pure luck because we don’t need to see those things, it’s not crucial to survival – but we can see them.

This article about the bat is an out-take from (that is, I didn’t put it into) my book about our awareness of (or lack of awareness of) our position in the universe.



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Filed under Philosophy, Science

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