Why do things look like other things?

Dandlion seedhead and sparkler
seeds radiating from the center - sparks radiating from the center

While attempting to organise my unwieldy, burgeoning collection of photographs from the patch I kept noticing something. My brain was continually making connections – "that lichen looks like cracked mud, that flock of birds resembles smoke, there's a face on that tree".

Why do things in nature often look like other, completely unrelated, things in nature? The answer to this points to a regularity, order and unity in nature...and to patterns.

Grain of an Oak tree and my thumb print
A random arrangement of gravel.
A pattern could be seen as anything
that isn't random

Patterns in nature are visible regularities of form - similar patterns appear again and again in  different contexts - in both living and non living things. Why is this?

I think there are three overlapping kinds of explanation.

1) Laws of nature - nature has no choice – it has to obey the physical laws of the universe. So a bubble is the shape it is because surface tension pulls water molecules of water into the tightest possible grouping…that happens to be a sphere.

2) Adaption - nature ‘wants’ (or perhaps it’s better to say ‘is adapted’) to look a certain way - a hoverfly looks like a wasp because mimicking something that predators avoid helps it to survive.

3) Perception There’s clearly a link between the existence of patterns and the perception of patterns. It’s certainly true that bubbles would be spherical, whether or not there were beings to perceive them as being spherical. On the other hand, an arrangement of bubbles in a coffee cup that looks like, say Australia – that’s something human beings, with their marked pattern finding proclivities, bring to the table.

Types of Patterns

Fractals
Zoom in to a part of Ferns or  cloud and they look pretty much the same

A  twig looks like the whole tree, a small part of a cloud mimics the whole cloud – why? because they are self similar. This is a very common feature in nature - trees, rivers, leaf veins, coastlines, mountains – they look pretty much the same irrespective of whether you are looking at the whole thing or a small part of the thing.

Where objects look similar at different scales of magnification they have a property called fractal. Fractal geometry has been called the ‘geometry of nature’. In nature it’s very difficult to find the perfect circles, straight lines and spheres or traditional Euclidean geometry, instead nature appears messy, jagged, irregular. However these seemingly complex forms reveal an underlying simplicity and a logic when viewed as fractals.

Sprirals

Spirals in  a pine cone and snail shell. The pine cone, like the sunflower seedhead, in fact has two spirals going in opposite directions

A bath emptying through a plug hole, tornadoes, snail shells, sunflower seedheads, pine cones - spirals abound in nature.

Should you wish to grow into spiral then simply adhere to this rule – keep the shape of the rim the same while gradually increasing the circumference, with faster growth on the outside than the inside.

As with many things in nature (probably everything in nature) there are a number of kinds of explanation for the existence of spirals.

1 Physics - spirals are the lowest-energy configurations which emerge spontaneously through self-organizing processes in dynamic systems.

2 Chemistry - a spiral can be generated by a reaction-diffusion process, involving both activation and inhibition.

3 Biology - arranging leaves (for example) as far apart as possible in space is favoured by natural selection as it maximises exposure to sunlight to for photosynthesis.

Bubbles
Dragonfly compound eyes and soap bubles - hexagonal packing (although, ideally the bubbles should be more uniform in size than my example, to show hexagonal packing)


A  bubble forms a sphere, a surface with the minimum area. Bubbles (of equal size) in a layer, pack themselves in the tightest way possible by forming hexagons and the compound eyes of insects are similarly hexagonal.

Bee’s honeycombs are also hexagonal. A Hard Darwinist – someone who believes that everything in the living world is shaped by natural selection - would contend that bees have evolved to use the honey in the most efficient way and so pack the honeycomb with hexagons.

There is another view however - bees simply make circular cells - the  laws of nature dictate that these will willy nilly  form themselves into hexagons, when arranged alongside the handiwork of fellow hive-members.

This is the view that evolution doesn’t have a clean slate to work with – it operates with the hand it’s been given.  It was first put forward by the brilliant Scottish mathematian D'Arcy Wentworth Thompson. His book 'On Growth and Form' is regarded as being decades ahead of its time. It led the way in the scientific explanation of  the processes by which patterns and body structures are formed in plants and animals. (very interesting BBC Radio 4 Program on D’Arcy Thomson)

D’Arcy Thomson's insight can be summed up by the simple quote:

"everything is the way it is because it got that way"

Cracks
Cracks in mud, lichen, tree bark

Cracks are linear openings in materials that form to relieve stress. Take tree bark for example, each species has its own pattern of splitting reflecting its own structure at the levels of cell and indeed molecules.

Meshes

Dragonfly wing and web of sheet web spider - composed of 'cells' - there is some similarity  here to the packing behaviour of bubbles in a foam.

Flow
Slime mold advancing over the surface of a dead tree to obtain nutrients. 

With a bit of imagination, and maybe a bit of squinting, the black and white version of the slime mold photograph on the right could be a aerial photograph of a river system with its tributaries. Both flow, avoiding obstacles and showing fractal branching patterns (they are different however in that water flow is due gravity)

Symmetry
Elephant hawk moth 

Something is symmetrical if it looks the same after it has been transformed – for example rotated or reflected.

Living things tend to be symmetrical partially as a consequence of the fact that they grow - and that growth is governed by simple rules. 

The Elephant hawk moth above, like 99% of animals, is symmetrical.  It locomotes, so is arranged with a front end and a back end. It is subject to gravity so it has a top and a bottom. There is an identical environment on either side so it has reflectional symmetry. (My previous post on symmetry)

Adaption
The Buff-tip is a very striking example of mimicry in moths - not only does it closely resemble a twig, but a broken twig and a silver Birch, broken twig at that

In terms of things looking like other things mimcry is rather different to those looked at so far. It's not a case of nature having no choice but to slavishly conform to the dictates of phyical laws. The Buff-tip moth has adapted over time, through natural selection, to resemble another object in its environment - a broken silver birch twig. 

This is an adaption which has come about in order to influence the brains of potential predators -  so as to be perceived as something other that a prey item.

Flowers have also evolved to influence brains - insect brains.  Their symmetrical, colourful patterns have evolved to attract the insects to their nectar 'bribe' in return for acting as pollinators.

Non living things adhere to the physical laws - all things being equal a bubble must be spherical.

Living things clearly cannot break the physical laws but the extent to which forms go
a)  'with the grain' of physical laws - the peacock has wings which are shaped in such a way as to enable flight.
b) 'against the grain' of physical laws - the male peacock's tail hinders efficient flight, but despite this it has come about through sexual selection

...is open to debate.

Human pattern recognition
Pattern formed by Ash pollen fallen on to a black card - with a bit of imagination this could be an image of distant galaxies

I took this photo of Ash pollen and in looking at it my brain performs a number of activities. It perceives the pattern which does actually exist -  that's to say the distribution of dots is not random they are clumped.

It also compares the pattern to other patterns in my memory. Passing over things such as a human pyrammids, Andy's Wharhol's soup tins and a conga line, it gets to the memory of  'galaxies as photographed by Hubble Telescope' - and declares 'congratulations you have a match'. My conscious brain then thinks 'hmm...that looks like distant galaxies'.

Pattern recognition is an innate ability of animals and humans are particularly good at it. We do it all the time - however it's happening behind the scenes so we're unaware of it.

I posted the unadulterated photo on the left (greenshield lichen on orange algae) on Facebook, someone remarked that they could see a face. For the second photo I rotated  and duplicated the eye-like bit - hey presto - it really does look like a face!

Take the act of reading for example - there's an enormous amount of pattern recognition going on. Firstly you recognize the patterns of individual letters, then the patterns of individual words, then groups of words together - after this has happened the patterns can be given meaning.

Consider a couple of cavemen and the famous sabre-toothed tiger (we'll call him Kevin), that always gets brought up in these kinds of discussions.  One sees a dangerous predator in the indistinct pattern of shadows outside his cave and takes evasive action.  The other doesn't register the danger and so gets eaten by Kevin. The first one survives and so passes on his genes for keen pattern recognition.

Pareidolia is the phenomenon in which the mind
responds to  an image by perceiving a
familiar pattern - faces are very common
such patterns
Many of the potential threats he sees will perhaps turn out to be false alarms, but when Kevin's on the prowl it's definitely much better to be safe than sorry.

Of all the patterns that humans recognise - faces are near the top of the leaderboard. For this reason we also jump to false conclusions about which configuration of visual stimuli triggers the 'it's a face! response. It's remarkable how little is required to be perceived as face-like - just a couple of dots and a line will suffice.

Luckily we often draw the right conclusion when it comes to - things looking like other things.

Imagine the embarrassment if you joined a queue in the post office, complete with party hat, a bottle of champagne and forced jollity - thinking it was a conga line!

Twenty-plume Moth Alucita hexadactyla. Birds and a few moths such as this one, have hit on similar solutions to producing structures enabling flight. So the moth looks like it has feathers

The harmony of the world is made manifest in Form and Number, and the heart and soul and all the poetry of Natural Philosophy are embodied in the concept of mathematical beauty.
D'Arcy Wentworth Thompson
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