Tuesday, 24 January 2006

Seven Deadly Colours – Andrew Parker ****

Andrew Parker has a mission to show us how important the eye is. This is technically the second book of a trilogy. The first, In the Blink of an Eye portrayed the development of the eye as one of the significant driving factors of evolution, triggering (in Parker’s words) an arms race that continues today. In Seven Deadly Colours, Parker moves on to show the significance of colour in life forms and its relationship with the eye. (Actually he argues that objects don’t really have colour, it’s only eyes that define colour, but this is a little specious, as long as you consider colour to be a measure of the wavelengths of light emitted.)
To show how important colour is, he divides the book into seven major sections reflecting the colours of the rainbow (with the unnecessary indigo removed and ultra violet thrown in). Each section also features one particular creature, though there are plenty of diversions and inclusions, and each section details one particular way of producing colour, because, as Parker points out repeatedly at the start of the book, where artists are limited to one way of making a colour – pigments – animals are much more versatile.
It’s a truly fascinating voyage of discovery, beginning with the technically obvious, but still somehow shocking observation that, were it not for the eye, animals (and plants) would not have colouration other than the natural tendency to absorb certain energies of light that results in blood being red or chlorophyll being green. Nature’s rich canvas of decoration, camouflage and warning would never have evolved.
The reason the book works so well is in part the intriguing challenges Parker gives at the start of each chapter – what, for instance are the strange, blue glowing “spirits of the sea” seen off the Philippines, or why was a tree frog that hid against green leaves blue – and also because the natural world has such convoluted colour mechanisms. This is perhaps best illustrated in one of Parker’s asides, mentioning a leaf beetle that should stand out easily, because its green colouration is much brighter than a leaf, and directional. It remains camouflaged because its crinkly outer casing diffuses the green until it’s a near match for a leaf surface. Conversely, the book also works very well because it isn’t just about the colours out there, but the way different eyes react to those colours – whether it’s a kestrel’s extra cones to deal with ultraviolet, or the marine mammals that have lost a valuable blue receptor and can’t get it back.
All this is excellent. Parker knows his creatures and their colour mechanisms, he has an enjoyable turn of phrase and this is a truly fun read when he is dealing with the biology. But there is a problem, which accounts for the four star rating – on the biology alone, the book would get five stars.
Unfortunately, as well as covering the biology, Parker attempts to put alongside it the physical science and here he falls down quite badly, because his ideas of physics are firmly rooted in the 19th century. It’s as if a physicist, trying to write a crossover book between physics and biology relied on a pre-Darwinian view of the world – it just doesn’t work. This dated attitude comes through right at the start when Parker repeatedly tells us how limited we are because our artists only make colours using pigments. True in his Victorian world. But out here, Andrew, the visual arts most people spend most time watching don’t rely on pigments at all, but on cathode ray tubes, LCDs and plasma. It’s something called TV.
The same time warp applies to Parker’s description of light, which is solidly rooted in pre-20th century wave theory. This is despite the fact that most of the phenomena he describes concern the interaction of light and matter, an interaction that is only sensibly described using quantum electrodynamics. Parker even unconsciously emphasizes this. In his introduction he quite happily describes “how light works” only referring to waves. But the first time he ever mentions a biological mechanism using light he immediately refers to a photon. Unfortunately he hasn’t given any indication of what this is, or what it has to do with his descriptions of ripples in a piece of string. The weakness of the physics extends to getting one point absolutely wrong. Parker tells us that the reason the sky is blue is because “fine particles and water molecules in the Earth’s atmosphere reflect the blue rays in sunlight down to the Earth’s surface.” While this Tyndall scattering occurs, and explains the phenomenon in a frog that Parker is describing, it’s not why the sky is blue.
That the book gets a four star rating despite this major flaw is because the biological aspect is so excellent. The book is well worth reading. But those who know a bit of physics must grit their teeth, and those who don’t are probably best ignoring the physical asides.
Review by Brian Clegg

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