We share our planet quite naturally with a permanent aeroplankton; a buoyant ecology too soft to hear, too small to see, but heavy with mood and meaning. Imagine being aware of all these airy inclusions - and you can begin to understand how it might feel to be able to smell really well.
Even the cleanest air, at the centre of the South Pacific or somewhere over Antarctica, has two hundred thousand assorted bits and pieces in every lungful. And this count rises to two million or more in the thick of the Serengeti migration, or over a six-lane highway during rush hour in downtown Los Angeles.
If elephants didn't exist, you couldn't invent one. They belong to a small group of living things so unlikely they challenge credulity and common sense.
Before sight and sound hijacked our attention, we shared with all life a sort of common sense, a chemical sense that depended on direct contact with matter in the water or the air.
Even in the lives of fishes, sensation is seldom a matter of one thing or another. Senses overlap. The lines between them often tend to be blurred, and the best that we can manage, by way of description from the outside, is to say that the senses of fishes appear to dominate one at a time.
Air is traditionally 'thin,' but the more we learn about our atmosphere, the more substantial it becomes. In some places it is so filled with inorganic flotsam that it is almost thick enough to plough; in others, it has become so primed with the by-products of life that it comes close to being a living tissue in its own right.
Breathing air is a liberating experience. It freed our ancestors from the constraints of staying wet or having to remain within easy reach of water for refuge, respiration or reproduction. But the biggest change it made in our lives was to expose us to a whole new range of sensory experience.
