The Umwelt: Life on the thin slice

[Umwelt = The ‘outer world’ perceived by organisms]

Spend a moment thinking about the most beautiful person you know. It would seem impossible for your eyes to gaze upon this person and not be intoxicated with attraction. This beautiful person, whoever they are, will make you mad and dizzy with love. But these feelings you have for this person depend on the evolutionary program your eyes are connected to. If these eyes of yours, belonged to a frog instead, this most beautiful person could stand naked in front of the frog for days on end – and attract not an ounce of attention, perhaps a bit of suspicion.

And this lack of interest is mutual: humans are attracted to humans, frogs to frogs, skunks to skunks.

Nothing seems more natural than desire, but the first thing to notice is that we are wired only for species-to-species desire. This underlies an important point: the brains nerve circuits are designed to generate behaviour that is appropriate to our survival. If a human was born with neural wiring that meant they he/she was more attracted to frogs than humans  – then that person would not reproduce and pass on those same traits. Hence, why humans are more attracted to each other! There is nothing inherently ugly about a frog, or a skunk, or a spider.

Apples and eggs and potatoes taste good to us not because the shapes of their molecules are inherently tasty, but because such foods are perfect packages of sugars and proteins: energy pounds(£) you can store in your body bank. It is because these foods are useful, that we are engineered to find them tasty. Because fecal (shit) matter contains harmful microbes, we have developed a hard-wired aversion to eating it. However, baby Koala bears eat their mothers fecal matter to obtain the right bacteria for their digestive systems. These bacteria are necessary for baby Koala’s to survive on otherwise poisonous eucalyptus leaves. If I had to guess, i’d say that fecal matter tastes as delicious to baby Koala bears as strawberries taste delicious to you. Nothing is inherently – absolutely – tasty or repulsive. It depends on your needs.

Deliciousness is simply an index of usefulness.

These same principles of hard-wired thought guidance also apply to all of your deeply held beliefs about logic, economics, ethics, emotions, beauty, social interactions, love, and the rest of your vast mental landscape. Our evolutionary goals navigate and structure our thoughts. Chew on that for a moment. It means there are certain kinds of thoughts you can think, and whole categories of thoughts you cannot.


In 1670, Blaise Pascal noted with awe that “man is equally incapable of seeing the nothingness from which he emerges and the infinity in which he is engulfed”. Pascal recognised that we spend our lives on a thin slice between the unimaginably small scale of the atoms, and the infinitely large scale of the galaxies. But Pascal didn’t know half of it! Forget about atoms and galaxies, we can’t even see most of what lies on our own scale!

Take what we call visible light for example. We have specialised receptors at the back of our eyes optimised for capturing the electromagnetic spectrum that bounces off objects. When these receptors catch some radiation from the outside world they launch a salvo of signals to the brain. But we do not perceive the entire electromagnetic spectrum, only a tiny fraction of it. In fact the part that is visible to us is less than a trillionth of it. The rest of the electromagnetic spectrum carrying TV signals, radio waves, microwaves, x-rays, cell-phone conversations, gamma rays, and so on – flow right through us! The BBC news is passing through you right now and you are utterly blind to it. Honey bees by contrast have receptors for ultraviolet light and rattlesnakes can see infra-red light as part of their world. We can’t see any of this. What we see and experience is limited by our biology. This is totally contrary to the commonly held belief that what we see is everything that is ‘out there’. It is clear that our brains sample a small fraction of what’s really out there.

The reason we don’t miss the ‘missing bits’ is because we’ve never gotten used to having them. What you don’t have you don’t miss. Every animal is different. In the blind and deaf world of the Tick, the important signals are temperature and smell of butyric acid. For the blind eel it is electrical fields. The part that you are able to see is known as the Umwelt in German, and the bigger reality is known as the Umgebung (these German words!). Each organism has its own Umwelt, which it assumes to be the reality “out there”.

Ask yourself what it would be like to have been blind from birth. No seriously really think about this for a moment. If your guess is “it would be something like darkness” or “something like a dark hole where vision would be” you’re wrong. To understand why, imagine you’re a scent dog like a bloodhound. Your long nose houses 2 hundred million scent receptors. On the outside, your wet nostrils attract and trap scent molecules. The slits on the corners of your nostrils flair out to allow more airflow as you sniff. Even your floppy ears drag along the ground and kick up scent molecules. As a bloodhound your world is all about smelling. The picture you create of the world is created mainly with the sense of smell. One afternoon, you’re following your master, and suddenly you stop in your tracks with a revelation. What is it like to have the pitiful, impoverished and useless nose of a human being?!

What can humans possibly detect when they take in a feeble little nostril of air? Do they suffer a blackness? A hole of smell where smell is supposed to be?

Because we are human we know the answer is no. There is no hole, or blackness or missing feeling where the scent is absent. You accept your reality as it is presented to you. As you don’t have the smelling abilities of a bloodhound it doesn’t even remotely strike you that you are missing something and things could be different. So the blind are not missing anything; they do not see blackness where vision is missing. Vision was never part of the reality of the blind in the first place, and they miss it only as much as you miss the extra scents of the bloodhound dog.

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