The inexorable spread of spectacles has been exercising the formidable brain of one of the world's foremost thinkers about evolution and human behaviour, an austere American biologist called George C Williams. Others, such as Oxford zoologist Richard Dawkins, may have made a bigger impact on the public at large, but the theory that Dawkins popularised so vividly in his best-seller The Selfish Gene sprang from the work and creative thinking of Professor Williams.
Evolution does not mean crude competition among individuals for the survival of the fittest; animals can and do show altruism towards each other, sometimes even sacrificing their lives for kin or unrelated members of their social group. In the mid-Sixties, Professor Williams showed that Darwinism could make sense of such behaviour, and so set the pace for the next three decades of evolutionary biology. From a focus on how bodies evolved physically, biologists shifted to the more controversial area of Darwinian explanations for animal behaviour - including human behaviour.
Now Professor Williams wants to apply Darwinism to medicine. "We are organisms designed for Stone Age lifestyles," he said. Many diseases of the modern world arise "not because of infection or injury, but from within ourselves". They stem, he believes, "from a mismatch between our present environment and the [Stone Age] one in which our adaptations were produced and fine tuned."
Professor Williams was in London this month to chair a Darwin seminar at the London School of Economics before flying to Basel to start organising the first European conference on Darwinian medicine. It is a new field, and the cornerstone is Evolution and Healing - The New Science of Darwinian Medicine, a book he has written with Dr Randolph Nesse, an American clinician.
What does Darwinism have to offer medicine? Myopia is a prime example. Medical students are taught that it has a genetic component, yet it could not have been a problem in the Stone Age; people who could not see well enough to avoid lions and tigers, or side-step spears thrown by rival tribes, would not last long enough to pass myopic genes to the next generation.
Professor Williams believes it results "from uses of the eyes in childhood and adolescence that are abnormal - too much close-up work at the cost of distance perception". He cited two studies showing that, as urbanisation sets in, a given population can go in a couple of generations from having no myopia to a high incidence. That is too short a time to be due to a change in the gene pool of the population, but "an environmental change brings out genetic differences which would not have been apparent in the original environment".
Another and perhaps less controversial example is the alarming incidence of hypertension, late-onset diabetes and similar conditions among Asian immigrants to Britain. Their environment has changed from one in which food was relatively in short supply to one in which fatty, sugary foods are available in abundance. Again, an environmental change has acted to uncover genetic differences which were there all the time but which would never have become manifest in the original environment.
But there is no place for gloomy biological predestinarianism in Professor Williams's version of Darwinian medicine. "The mismatch between our present environment and our adaptation is a problem that's not going to be solved by human evolution - it must be solved by the realisation that some of our natural tendencies are in fact harmful." There is the hint of asceticism about him - "habit and discipline are required" to circumvent the deleterious effects of our modern diet - a trait which is visually reinforced by his striking appearance, as if this man had been carved from the rock of Mount Rushmore.
Now aged 69, he is emeritus professor of ecology and evolution at the State University of New York and regarded as a sage by a younger generation of biologists. In his book, The Moral Animal, published last year, Robert Wright, writes: "In 1966, Williams published his landmark work - Adaptation and Natural Selection. Slowly, this book has acquired a nearly holy stature in its field. It is a basic text for biologists who think about social behaviour, including human social behaviour." According to Richard Dawkins in The Selfish Gene, "Williams's book has now become widely, and rightly, regarded as a classic."
He flinched when I suggested that Evolution and Healing outlines a somewhat "holistic" approach to medicine by focusing not just on the proximate causes of disease but also on the broader context of how evolution may have predisposed us to some conditions. "I would hate to be associated with other groups," he says. "Frequently, it's just mysticism, vagueness and wishful thinking." He pauses, then says: "If the term is used legitimately, it would be applicable." Professor Williams's thinking, one feels, will always be as precise as its expression is terse.
But although he trims his beard in the manner of a God-fearing 19th-century American pioneer, the outward impression of austerity is softened by Williams's ready statement: "I am not inclined to abandon any comforts of the modern environment. We are really much better off now than any other people have been throughout history. I hope my message is not gloom and despondency. We can be optimistic that [Darwinian] insights and research will result in health improvements."
Nor need we revert to being illiterate peasantry to combat shortsightedness: "There may be quite simple things we can do to prevent myopia." Professor Williams suggests that researchers should investigate whether it would be better for slightly myopic 10-year olds not to be equipped with corrective lenses, because their eyes will accommodate the lenses to make their sight even worse. Other suggestions which should be investigated are children's books with bigger print and wider margins, and the use of blackboards and other distant images rather than books to teach reading.
Like the other ailments relevant to Darwinian medicine, myopia is in our genes, but it is also in our environment, and Professor Williams has little time for those who consider the effect of genes divorced from the environment in which those genes are expressed. The phrase "environmental change" appears in his conversation far more often than any mention of genetics. He adamantly rules out the idea that humanity should "assist" evolution or that Darwinism offers any moral or social guidance on what ought to be done.
Some social commentators have sought social ends in Darwinism, most notably the American academics Richard Herrnstein and Charles Murray in their book The Bell Curve, which suggested that the American poor and black population are genetically pre-ordained to form a social underclass. Professor Williams greeted mention of the book with a moment's silent distaste, then said: "I can't imagine any support for that proposition. Lots of people have taken terms from biology and used them metaphorically for ends which are, from my perspective, undesirable."
It would be precisely the sort of metaphorical use he criticises to point out that the social perspective of the creator of the evolutionary concept of altruism is clearly altruistic in the ordinary sense. He has been a regular supporter of Amnesty International for more than 15 years, and there are hints of ascetic scepticism about American consumer society: "People are manipulated by commercial organisations to buy things they don't want and won't benefit from."
He believes that real biology, as opposed to slack use of biological terms, cannot be hijacked for illegitimate purposes. Biology describes the world as it is, not the way it ought to be. The point of Darwinian medicine, according to Professor Williams, is this: "It would be legitimate to derive public health policies from Darwinian insights if they tell you how to prevent disease. For insights on what you ought to accomplish? No. Darwinian insights come in at the tactical level - how to realise these goals once we have decided on them."