If water is clear, why is the sea blue?
If we see through air, why is sky blue too?
Not all sources produce white –
Wood fires make an orange light.


Use this part of the book to establish that expectations about answers to the question ‘Why’ are often not appropriate.

This issue will crop up many, many times.

The issue with ‘Why?’

It seems natural to ask ‘Why?’   Why is that donkey from Nevada brown?  Why did it not paint itself in black and white stripes like the zebra, or tip a can of fluorescent pink paint over itself like this slug from Australia, or choose red and green like a King Parrot?   

‘Why?’ questions are common but sometimes they are not appropriate. 

‘Why?’ is appropriate when you are thinking of a system that is based on rules. Math does this with “1+1=2”, Pythagorus’ theorem that the sum of the square of the hypotenuse is equal to the sum of the squares of the other two sides, and so on.  Simple physics is the same. The existence of rules is what allows a pool-player to know that when they hit the white ball with this amount of force, in that direction, and with such-and-such spin, they can predict, when it hits its target,  the direction and distance that target ball will go.

‘Why?’ is also appropriate when there is a cause or purpose.  Why do we drive on one side of the road, not both? Why is the hot-plate hot?  Why are wheels round? Why should I not steal? Why is there ink in a pen?  Why do we take painkillers when our head hurts? Why do we wear warm clothes in winter and light clothes during the summer?   

Not all ‘Why? questions make sense. We have a letter ‘L’ in the alphabet, but not a letter ‘Γ’.   Why do some languages write from right to left, or up-and-down?. Why do we nod our heads to agree and shake them to say ‘No’, but in some countries, people shakle their heads to say ‘Yes’.  

Most people would like there to be an answer to all ‘Why?’ questions in Science.  That is not the case. When we see that sharks have sharp teeth that will grab and destroy prey, it is easy to imagine that these teeth were designed with a purpose in mind. And, if these bits of biology have a purpose, then surely all bits of biology are purposeful.  That is incorrect thinking.

The teeth of the shark were not designed to grab and destroy prey.  Over 150 years ago, Charles Darwin explained how the features of organisms appear by chance.  Within any species, there are some that are bigger, smaller, more brightly colored, or faster.   This is called ‘variation’.  Some individuals in a species of shark will have more teeth than others, some will have sharper teeth, and some will have longer teeth. Variation happens because of the way that information is inherited from one generation to the next or how that information is converted into a feature in an organism. Mostly the information is passed on in an exact form, but sometimes the information is muddled up. Sometimes, when young develop, they are not exactly like their parents.  Humpback whales are a dark gray color, and yet sometimes a completely white whale is born.  They are called albinos.   This change in color is  caused by mutation, when some part of the genetic information is disrupted.   

Two tourists in Africa are taking pictures of lions. Suddenly, it looks as if the lions are getting hungry. One tourist turns and runs, the other says – ‘Why are you running, the lion can run faster than you. You cannot get away.’   The response is “I’ll be OK if I can get away  faster than you’.   That is, under some very special circumstances, some aspect of variation will be of benefit.  If the young shark just happens to have better teeth than its brothers and sisters, it is the one more likely to catch and hold prey.  And if there is not much food out there, it will be the one to survive. It will pass on its unusual features to its own children.  This is ‘selection’.  So, selection leads to improvements. The variation that selection relies on comes from completely pointless changes in the genetic makeup of the organism.    

Variation and mutation do not have purpose. They just happen.  Sometimes, the change is so severe that the organism will not survive, mostly the changes are relatively benign. While an albino whale is much more obvious than normal whales, these whales are so big that they are at no greater risk of being attached by a predator just because they are white. The same is not true when the animal in question in much smaller, an albino squirrel is much more likely to be seen by a hawk or coyote.  

A lot of variations create organisms that cannot survive. Other have absolutely no consequence for the bearer.  They persist.  Examples of this include the color of hair; or the color of the irises of the eye. 

Variations and mutations  matter when they improve or damage the survival of an organism. When a herd of zebra is being attached by lions, the key to survival is not being the slowest.   Any variation or mutation that makes zebras slower, makes those animals more vulnerable. The animals with the genetic information for ‘slower’ are more likely to be eliminated, and only the faster members of the herd survive.  

The answer to ‘Why?’ may well be because the feature in question, such as the color brown of the donkey, has remained because over the millions of years the donkey has been here (Earth not America … Columbus brought the first to America from Europe), this color has made the animal more fit.  It blends better with the ground, and is more likely to be overlooked by a mountain lion that is feeling hungry.

But, with this answer we are guessing.  There is no rule that says donkeys must be brown. There was certainly no intention that  converted the non-brown ancestors into brown donkeys.  

Under these circumstances, it is better to turn the question slightly.  That is a brown donkey. What do you think are the advantages of it being brown?

Or, to go one step further, look again.  That donkey is dark brown above and light tan below.  What do you think are the advantages of it having two tones of brown?


Some surfaces absorb, like black
All is gone, nothing comes back.
Others reflect and strengthen a hue
In animals this is often true for blue.

Why should this damselfly, a bluet, be such a garish color. If we try to list the benefits and the disadvantages, surely we would put on the list that this bright blue insect would be visible from miles away by any insect-eating bird.  It is not wise to be so obvious.   Add another factor … damselflies mostly live around the edges of lakes and ponds.  On nice sunlit says, the water will reflect the sky, and the ripples on the water will sparkle bright white and blue. Here, maybe, there is a benefit from being bright blue – less easy to see when perched on a weed at the water’s edge.   

There is more, while the male bluet is very bright, the female ones are a duller brown color.  In that regard, they are like the donkey.  They would be harder to see if sitting in bushes.    In many cases, males are brightly colored, and females and young are not.  The glorious eyes of the peacock are of the Mr Peacock, not the Ms Peahen.  The Mr Frigate bird has a great red balloon under its chin that it can inflate, but  Ms Frigate birds do not have this.   One argument is that the colors are a way for the males to show off to the females, and the more brightly colored, and more extravagant their displays, the more likely they are to be chosen, and more likely to father the next generation.  Another idea is that if a bluet is going to be eaten, better to sacrifice the male than the female – because she may be carrying eggs, and if she goes, so does the next generation. 

Which opens up new issues when you think about ‘What could be the benefits of that!’  Think about benefits to the individual, benefits to the gender, and benefits to the species.  

Mangroves, blue sea, purple sky

Particles in this water reflect more light,
Making the sea’s blue a bit more white.

Strange sky, strange water.

This landscape picture is included because two colors here, not of living nature but still of the natural environment, look wrong. The sky is purple, and the sea is a light, almost white, blue.  How or why could that be. 

Purple is what you get when you mix blue and red.  The land, here, is a bright red color.  It is a very dusty kind of soil, and the dust is easily blown into the air.  The purple is because the blue color of the sky had been combined with red reflections from the dust particles. 

The sea also has some tiny almost glassy particles that have been eroded from local rocks.  These particles are a little like glitter, they reflect sunlight that penetrates into the sea.  The resulting white reflections give the sea its milky color.

Bottle brush flower with bagworm case
Bottle brush flower with bagworm case

A bottle brush flower
Whose scarlet tower
Gives shade to a log cabin
Its bag worm huddled within.



  • Dot point with  Linkout
  • Dot point with let’s find out 
  • If you have more ideas, more examples of  color patterns that do not make sense, do let us know below.
Nature Reader colors web Why

Leave a Reply