Evolutionary artifact

Richard Dawkins writes in River out of Eden about research showing ‘how the first living photocell came into being by step-by-step modification of an earlier, more general-purpose cell.’

He speaks about skin as tissue, as is the lining of the intestine, muscle and liver. Like the rest of our physiology ‘tissues can change in various ways under the influence of random mutation. Sheets of tissue can become larger or smaller in area. They can become thicker or thinner. In the special case of transparent tissues like lens tissue, they can change the refractive index (the light-bending power) of local parts of the tissue.’ [New York, Basic Books, 1995, pp.77-83]

The beginning of the human eye likely evolved from the ever-thinning skin membrane of an underwater being. J. Craig Venter, who voyaged the world like Charles Darwin did in The Beagle about 150 years ago, was surprised to find so many underwater beings having light-sensitive membranes.

Our salty tears are a reminder of an oceanic origin now long gone. The first animals with anything resembling an eye lived about 550 million years ago and that it would have taken about 364,000 years, not terribly long in evolutionary terms, for a camera-like eye as we have to have evolved from a light-sensitive patch or membrane. Many animal species see with their ears – like dolphins and bats - observes Diane Ackerman in her Natural History of the Senses – ‘but for us the world becomes most densely informative, most luscious, when we take it in through our eyes. It may be', she speculates with literary license ‘that abstract thinking evolved from our eyes’ elaborate struggle to make sense of what they saw.’[New York, Vintage, 1995, p.230].

Our eyes are forward facing and we, like other predators, have binocular vision. We see reasonably well (but not as well as a cat). We see a particular range of colours during the day that then turns into monochromatic vision at night.

It may be that some individuals, and among them visual artists, experience colour perception more intensely than others. There is the view that visual artists experience colour more flamboyantly than the rest of us ordinary mortals. Ackerman observes ‘that extraordinary artists come into this world with a different way of seeing. That doesn’t explain genius, of course, which has so much to do with risk, anger, a blazing emotional furnace, a sense of aesthetic decorum, a savage wistfulness, lidless curiosity, and many other qualities’[p.270].

The National Gallery of London held a special exhibition of the work of Edgar Degas who excelled in the use of colour to express the full range of human emotion, his drawing, pastels, oil paintings, printmaking, sculpture and framing, and of course for which his rendition of the Russian Dancers of 1899 and Ballet Dancers painted in the 1890s in the great boldness of his red were exceptional. The exhibition, funded by Mobil Exxon and where Hewlett Packard was a creative partner in image reproduction, Degas’ techniques and use of colour in the greatness of his art were examined in detail. [Art in the making; Degas (London, National Gallery, 2004]. Degas clearly loved colour.

Charles Darwin observed in the Origin of Species that ‘to suppose that the eye, with all its inimitable contrivances for adjusting the focus of different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurb in the highest possible degree’ [Oxford, 1996 Edition, p.152].

Darwin was countering his critics in anticipation. It turns out that he was right, that the human eye is a consequence of natural selection acting on transparent tissue. Venter discovered eyes corresponding to every evolutionary sequence that mammals and hominids must have had can be found among living oceanic species today.

Eyes give their owners a monumental advantage in the struggle for survival. Being able to see in colour is even better. Sight has a cost, however. It takes considerable brain power, neural wiring and energy to keep sight going. Perhaps this is why of the 38 categories of multi-cellular beings only 6 have eyes. As perhaps a testimony to the power of sight, over 95 per cent of living species today belong to those very 6 categories that are able to form images on their retina, to, in other words, harvest light, the stimulus for vision.