Saturday, May 14, 2005
Invisible Ink
There's a fascinating review in The Telegraph today of Andrew Parker's Seven Deadly Colours: The Genius of Nature's Palette and How It Eluded Darwin:
The eye was "Darwin's nemesis". As Parker explains in Seven Deadly Colours, Darwin was led to doubt his theory's universal validity by misunderstanding the process of vision. Parker describes seven examples of behaviour in the natural world that would have been beyond Darwin's ken, yet which modern ideas about light and perception render comprehensible.
In his first example, Parker asks why kestrels hover over motorway verges, where their prey of brown voles are well camouflaged and therefore especially hard to see. The answer, Parker explains at length, is that kestrels can detect the likely presence of voles through their trails, which have ultraviolet pigments... which human eyes are unable to see...
In another conundrum, Parker asks how the American milk snake, whose skin has bands of orange, black and white, successfully camouflages itself in green grass, where it should be plainly visible to predators that view it as a good dinner. It turns out that the solution lies in an old optical demonstration in which a rapidly rotating black-and-white disc appears to be coloured - the rotation tricks our eyes into believing that the disc is coloured. Parker convincingly argues that the swift motion of the milk snake fools its predators into seeing only olive green and so becomes hard to discern among the grass.
Unfortunately, although Perseus published a US edition of Parker's previous book (In The Blink of An Eye), I don't see any indication of a US publisher on this new one. Powell's Books, however, does carry the UK edition for $31.50.
The eye was "Darwin's nemesis". As Parker explains in Seven Deadly Colours, Darwin was led to doubt his theory's universal validity by misunderstanding the process of vision. Parker describes seven examples of behaviour in the natural world that would have been beyond Darwin's ken, yet which modern ideas about light and perception render comprehensible.
In his first example, Parker asks why kestrels hover over motorway verges, where their prey of brown voles are well camouflaged and therefore especially hard to see. The answer, Parker explains at length, is that kestrels can detect the likely presence of voles through their trails, which have ultraviolet pigments... which human eyes are unable to see...
In another conundrum, Parker asks how the American milk snake, whose skin has bands of orange, black and white, successfully camouflages itself in green grass, where it should be plainly visible to predators that view it as a good dinner. It turns out that the solution lies in an old optical demonstration in which a rapidly rotating black-and-white disc appears to be coloured - the rotation tricks our eyes into believing that the disc is coloured. Parker convincingly argues that the swift motion of the milk snake fools its predators into seeing only olive green and so becomes hard to discern among the grass.
Unfortunately, although Perseus published a US edition of Parker's previous book (In The Blink of An Eye), I don't see any indication of a US publisher on this new one. Powell's Books, however, does carry the UK edition for $31.50.
