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The Origin of Eyes

Date:
Byline: By Valerius Geist
Lead:

CLIMBING MOUNT IMPROBABLE
By Richard Dawkins.
Illustrated. 340 pp. New York:
W. W. Norton & Company. $25.

Reading the first two chapters of this book, a student of evolution might wonder why it was written in the first place. Technically it is not contentious. It is not news today that organisms change progressively and nonrandomly through natural selection and that new hereditary information is supplied by a stream of mutations in the hereditary molecules (DNA) and in the chromosomes. Nor is it news that adaptive structures mimic ''design'' and astonish with their ''perfection.'' Why should Richard Dawkins, who holds the chair in the communication of science at Oxford, be so concerned to explain what his peers in evolutionary biology would hardly contest?

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In the third chapter one discovers the answer. The reason is the persistent and gross misunderstanding of Darwinian evolution, not only by laymen but in particular by physicists in Britain, including members of the Royal Society. Pointing to their status as physicists, they proclaim boldly that organisms cannot possibly arise by chance processes. Indeed they cannot. Nor does Darwinian evolution claim they do, certainly not in the caricature of evolution flaunted publicly by these physicists. Not only do they give aid and comfort to creationists, but their lusty, self-righteous critique throws shadows on their scholarship and raises a question about what distinction membership in the Royal Society might confer. Surely the first concern of disinterested scholars going public must be an accurate comprehension of the postulate they criticize. Reading remarks by these people is an excellent antidote to the ''physics envy'' that, regrettably, haunts biological and social sciences.

So this white knight sallies forth to fight the good battle against the black dragons of ignorance and careless scholarship. ''Climbing Mount Improbable'' is, therefore, another attempt to explain Darwinian evolution. It focuses on how natural selection generates complex organs, including one organ in particular, the eye. Charles Darwin admitted he was stumped to explain its evolution. However, what Darwin couldn't do, Mr. Dawkins can. Chapter 5 explains, step by step, the evolution of organs of vision. It is a masterpiece. Like much of this book, this chapter was screened by colleagues who had the expertise to insure accuracy, and whose help Mr. Dawkins properly acknowledges. A skilled writer and spellbinding storyteller, he summarizes current research to explain how structures like spider webs, organs of flight and sight, snail shells or the complex mutualism of fig trees and tiny wasps that act as pollinators could evolve.

I would recommend this book as supplementary reading in an introductory university course on evolution, but not without a word of caution. Whether the book is a masterpiece or not, its scope is quite narrow; there is some painful oversimplification and a number of irritants. Mr. Dawkins is solely concerned with what one may call ''efficiency selection,'' namely, when shortages of material resources generate a reproductive payoff for individuals that -- somehow -- manage to spend less of the precious resources on body maintenance and growth and thus proportionately more on reproduction. Designers also strive for this ideal and draw attention to it with the slogan ''Less is more.'' However, there are regimes of natural selection based not on poverty but on wealth, on superabundance of material resources, whether they are seasonal or circumstantial. Eyes and spider webs are organs of utility, and their evolution through efficiency selection runs by somewhat different rules from those of ''luxury organs,'' such as deer antlers and peacock tails.

Mr. Dawkins's time frame for evolution is too optimistic. After all, organisms act to defeat natural selection, to escape from evolution. Mr. Dawkins pays no attention to adaptive phenotypic plasticity -- an organism's ability to alter its physiology to accommodate changes in its environment -- which normally thwarts natural selection on genes. Thus a false impression is conveyed that genes (mutations) generally produce the same results. They rarely do. Organisms vary in size, in form and structure and in other ways based on the environment they exploit, so that identical genetic constitutions can give rise to very different shapes and behaviors within the same species, depending on the environment they experience during early growth and maturation. While natural selection is continuous, evolution begins only when individuals in a population cannot adjust to environmental stresses with existing abilities. Mutations whose effect can be overridden by the normal abilities of individuals spread randomly and, at best, become part of the genetic load of the species. We expect evolution (genetic change) to be rare, and when it does occur, it is proof of incompetence, of extinction barely avoided. Successful forms do not evolve noticeably as they deal competently with environmental vagaries. To be a ''living fossil'' is the hallmark of biological success.

Ice ages were not ''terrible,'' as Mr. Dawkins says, nor were they the executioners of deer with thin hair coats. Quite the contrary. Ice ages were most supportive of large mammals, humans included, as evidenced by superior physical development. Paradoxically, the change from glacial periods to interglacial ones was terrible, marked by extinctions and poor physical development among survivors. The size, braininess and health of our wild ice age ancestors (or of deer) has not been equaled in postglacial eras. Nor do deer, survivors of dozens of major glaciations, respond to cold by growing longer hair or dying. Rather, they step out of the cold into known pockets of protective microclimate. When I studied deer, I followed them when blizzards struck and saved my hide.

There are some other problems with the book that may not interest a general reader. But people in the field will find amusing examples of Mr. Dawkins's using arguments for which an influential geneticist of the past, Richard B. Goldschmidt, has been much maligned by Mr. Dawkins's fellow neo-Darwinians.

Might Mr. Dawkins's book change the mind of creationists and hostile physicists? Can he convert people Darwin could not? I doubt it. After all, Darwin's ''Origin of Species'' was addressed to the general public too, not just to his peers, and Darwin wrote clearly. However, in reaching out to a broad audience, Mr. Dawkins might help to dispel from receptive minds ignorant criticism of evolution. If so, his book will be of service to science and society.