• Email
  • Print

Why Darwin?

lewontin_1-052809.jpg
Royal Photographic Society
Charles Darwin, 1868–1869; photograph by Julia Margaret Cameron

When I was a student I was enjoined to reject the “Cleopatra’s Nose” theory of history, so called after Pascal’s remark in the Pensées : “Cleopatra’s nose: if it had been shorter, everything in the world would have changed.”1 The intent was not to dismiss biography as a way into the structuring of a historical narrative, but to reject the idea that the properties, ideas, or actions of some particular person were the necessary conditions for the unfolding of events in the world. If Josef Djugashvili had never been born, someone else could have been Stalin.

Despite this injunction, a remarkable amount of the history of science has been written through the medium of biographies of “great” scientists to whose brilliant discoveries we owe our understanding of the material world, and this historical methodology has reinforced the common notion that history is made by outstanding individuals. No respectable historian would claim that if Newton had never been born we would still be ignorant about gravitation. Yet we still refer to the regularities of the behavior of physical bodies as “Newton’s Laws,” the general regularities of simple inheritance as “Mendelism,” and the science of biological evolution as “Darwinism.” Even the famous history of science written by the Marxist J.D. Bernal is a recounting of the discoveries and inventions of individuals.

It would be wrong to say that biography is the sole, or even principal, present pathway into an understanding of the history of science. Certainly since Robert Merton’s founding of modern studies of the sociology of science in his 1938 work on seventeenth-century English science,2 the social milieu in which the problems of science arise and the institutional structure of scientific investigation have been central to our understanding of the history of scientific work. There are, however, occasions on which there are orgies of idolatrous celebrations of the lives of famous men, when the Suetonian ideal of history as biography overwhelms us. For Darwinians, 2009 is such a year.

It is the two hundredth anniversary of Darwin’s birth, and because, whether by chance or design, Darwin published his famous work when he was fifty, it is the 150th anniversary of the appearance of On the Origin of Species, It is not clear at what intervals such commemorations might occur. I myself have been a participant in international symposia on the one hundredth anniversary of the appearance of the Origin in 1859 and the one hundredth anniversary of Darwin’s death in 1882, both of which were attended by leading scientists of the time and resulted in commemorative volumes.

Neither of those occasions, however, was marked by the immense outpouring of Darwinalia that has marked the current occasion. On my desk are fifteen works that have just appeared, of which eleven are biographical, including two selections of Darwin’s letters, two books about the Origin, and two books concerned with explicating and commenting on evolutionary biology and its implications; but none deals either with the history of evolutionary thought before Darwin, or in any detail with his contemporary, Alfred Russel Wallace, the acknowledged independent inventor of the theory of evolution by natural selection, or the socioeconomic milieu in which Darwin and Wallace worked. Beyond these publications there are plans for two dozen commemorative gatherings of scientists, historians, and philosophers, so many indeed that some had to be put off until next year so that busy evolutionists could fit them into their schedules.

Of the books that have appeared this year that are directly related to the history of nineteenth-century evolutionary theory, two are clearly worth attention. One is Janet Browne’s Darwin’s Origin of Species, which is an excellent short excursion through the origin of Darwin’s book, its argument, its publication, and the controversies it engendered. It ends with an all-too-brief summary of the history of modern evolutionary genetics and the attempts to demonstrate natural selection in action in nature, as well as a quick visit to modern creationism.

These subjects deserve a treatment in extenso while some of the participants or their immediate students are still among the living, perhaps by a collaboration of a sophisticated and knowledgeable historian like Browne with someone in the thick of it. The other work of interest to the reader of the Origin is an annotated text of the first edition, juxtaposing a facsimile of Darwin’s publication with an extensive page-by-page commentary by James Costa. Costa makes use of his experience as a field naturalist and his knowledge of the modern literature of evolutionary biology to illumine many passages in Darwin’s work.

Why do we call the modern theory of organic evolution “Darwinism”? Charles Darwin certainly did not invent the idea of evolution, that is, of the continuous change in time of the state of some system as a fundamental property of that system, or even the idea that a process of evolution had occurred in the history of life. The study of the evolution of the cosmos itself was founded in Kant’s Metaphysical Foundations of Natural Science in 1786 and Laplace’s nebular hypothesis of 1796. Sadi Carnot’s second law of thermodynamics, the principle that over time all differences in energy between bits and pieces of the universe decrease, was published in 1824. The idea that the various geological formations observed on earth were not the result of a unique catastrophe or Great Flood, but the consequence of repeated and continual geological processes still going on at present, was postulated before the turn of the nineteenth century by James Hutton and long since accepted by 1859.

By the time of the appearance of the Origin, the physical sciences had become thoroughly evolutionary. Living beings were not seen as an exception. In 1769, Diderot had his dreaming philosopher d’Alembert wonder what races of animals had preceded us and what sorts would follow. He provided the motto of evolutionism as a worldview: “Everything changes, everything passes. Only the totality remains.” Darwin’s grandfather, Erasmus, in his epic The Temple of Nature of 1803, invokes his Muse to tell “how rose from elemental strife/Organic forms, and kindled into life,” and the Muse completes the evolutionary story by telling him that even “imperious man, who rules the bestial crowd,/…Arose from rudiments of form and sense.” By the younger Darwin’s time, the idea of organic evolution had become a common currency of intellectual life. Two years before the publication of the Origin, Herbert Spencer argued for a belief in organic evolution on the basis of the agreed-upon universality of evolutionary processes:

It is now universally admitted by philologists that languages, instead of being artificially or supernaturally formed, have been developed. And the histories of religion, of philosophy, of science, of the fine arts, of the industrial arts, show that these have passed through stages…. If, then, the recognition of evolution as the law of many diverse orders of phenomena has been spreading, may we not say that…evolution will presently be recognized as the law of the phenomena we are considering?

If Darwin (and Wallace) did not invent the idea of evolution or its application to the history of life, then at least it might be claimed that they invented a natural historical theory of the cause of that evolution. But they were not the first to do so. Jean-Baptiste Lamarck, in a succession of works between 1801 and 1809, provided a biological theory of adaptive organic evolution based on the supposed inheritance of changes acquired by organisms in the course of their individual lives. The example often cited is the roughly six-foot increase in the length of giraffes’ necks from their ancient origin as deer-like animals. If giraffes in any generation stretched their necks, even slightly, to feed on leaves higher up in trees, and if that slight increase in length were passed down to their offspring, then over many generations the cumulative effect would be the extraordinary shape of the modern giraffe.

Lest the sophisticated readers of TheNew York Review of Books regard this as a hopelessly outmoded nineteenth-century view of biology, it should be pointed out that until about fifteen years ago a neo-Lamarckian institution affiliated with the University of Paris, the Laboratoire d’Évolution des Êtres Organisés, carried out scholarly research on evolution that took seriously the possibility of the inheritance of acquired characteristics.

The Darwin-Wallace explanation of evolution, the theory of natural selection, is based on three principles:

1) Individuals in a population differ from each other in the form of particular characteristics (the principle of variation).

2) Offspring resemble their parents more than they resemble unrelated individuals (the principle of heritability).

3) The resources necessary for life and reproduction are limited. Individuals with different characteristics differ in their ability to acquire those resources and thus to survive and leave offspring in the next generations (the principle of natural selection).

It seems amazing that two naturalists could independently arrive at the same articulated theory of evolution from a consideration of the characteristics of some species of organisms in nature, their geographic distribution, and their similarities to other species. This amazement becomes considerably tempered, however, when one considers the social consciousness and economic milieu in which the theory arose, a milieu marked by the rise of competitive industrial capitalism in which individuals rose in the social hierarchy based, presumably, on their greater entrepreneurial fitness.

Darwin’s maternal grandfather, Josiah Wedgwood, started life as a potter’s apprentice and rose to be a member of the circle of new Mid- land industrial magnates along with James Watt, James Keir, and Matthew Boulton. While the nineteenth-century theory that some rose and some fell in society depending on their personal strengths and weaknesses is often referred to as “social Darwinism,” we would be much more in agreement with historical causation were we to call Darwinism “Biological Competitive Capitalism.” The perceived structure of the competitive economy provided the metaphors on which evolutionary theory was built.

One can hardly imagine anything that would have better justified the established social and economic theories of the Industrial Revolution than the claim that our very biological natures are examples of basic laws of political economy. How else are we to explain the immediate and continued commercial success of Darwin’s books? The entire first edition of 1,250 copies of the Origin was immediately snapped up by booksellers. The expectation of public interest is revealed by the fact that a circulating library took five hundred copies.3 The sixth edition, only thirteen years later, sold 11,000 copies. One cannot understand the origin and the immediate success of the Origin outside of the social and economic setting in which it was conceived, nor have historians of science ignored the question. The pages of the Journal of the History of Biology have certainly not been devoid of papers on the subject. Yet what we have been provided with in 2009 is biography and annotations on the Origin, Perhaps it is time for a socioeconomic analysis of our own preoccupations.

The parallel between the arguments for natural selection and nineteenth-century economic and social theory, however, misses an extremely important divergence between Darwin and political economy. The theory of competitive socioeconomic success is a theory about the rise of individuals and individual enterprises as a consequence of their superior fitness. But even though the Industrial Revolution resulted eventually, at least in some countries, in a general rise in material well-being, the number of immensely successful entrepreneurs is evidently limited precisely because their success depends on the existence of a large mass of less successful workers. No population can consist largely of people like Henry Clay Frick.

The theory of evolution by natural selection, in contrast, is meant to explain the adaptation and biological success of an entire species as a consequence of the disappearance of the less fit. Provided that a species does not become so numerous as to destroy the resources on which it depends, there is no structural reason why every individual of that species cannot be highly fit. If we seek a true originality in the understanding of Darwin and Wallace, it is to be found in their ability to adapt a theory meant to explain the success of a few to produce a theory of the success of the many, even though the many may be competing for resources in short supply. Whether they were conscious of this divergence of the theory of evolution by natural selection from the reigning economic and social theory is a question.

Despite the intuitive appeal of the theory of evolution by natural selection, there is a deep flaw in it as it was conceived in the nineteenth century, a flaw that was potentially fatal: it lacked an understanding of heredity. This problem was first pointed out in 1867 by a Scottish engineer, Fleeming Jenkin, but it does not seem to have had any effective force. From the observations that Darwin (and breeders) made about domesticated animals and plants, the most likely basis for the inheritance of characteristics seemed some sort of mixture of an internal fluid. If, for example, a large-bodied variety was mated to a small-bodied one, the usual outcome was offspring of intermediate size.

The problem is that if inheritance proceeds by a blending mechanism, then new variants in a species would rapidly be lost by dilution through mating with the common form. Suppose a variant individual appeared that was larger than normal. That individual would necessarily mate with the normal type and their offspring would be intermediate. When those few intermediate offspring mated it would almost certainly be with the vastly more numerous normal form so that the next generation of this family would be yet closer to the usual type. After a few generations of this process of dilution by crossing, there would be no detectable variation on which natural selection could operate, even if a larger type would be of some selective advantage. The reduction of variation by half with each generation is a vastly more powerful force than any biologically reasonable countervailing difference in reproductive fitness.

The Darwinian mechanism would, in fact, not work in a world of blending inheritance. Unknown to Darwin, Wallace, or any of the enthusiasts for the claim of evolution by natural selection, work by an obscure monk in the Königenkloster at Brno in Moravia would turn out to save the theory. Mendel’s experiments on peas demonstrated that inheritance was not based on the blending of some fluid-like material, but by the passage of particles that maintained their individual properties even when mixed together in a hybrid. Thus, in future generations, variant properties would reappear even though what we now call the genes for those variants were temporarily mixed with the normal gene forms in hybrids.

The journal of the Brünn Society of Natural Science in which Mendel’s research was published would never have been read by the English scientific establishment, nor indeed by anyone in the major centers of nineteenth-century natural science. It was not until 1900 that Mendel’s work was rediscovered as a consequence of the appearance of new scientific results on crossing plants. In full historical justice, if we are to personalize our modern explanation of evolution we should call it not “Darwinism,” nor even “Darwin-Wallacism,” but “Darwin-Wallace-Mendelism.”

The present understanding of natural selection of chance variants—variants produced through mutations of genes—as the basis for adaptive evolution obscures the historical fact that in the eighteenth and nineteenth centuries evolution was accepted as a reality but other scientific explanations for it existed and came into competition with “Darwinism.” Lamarck’s theory of the inheritance of acquired characteristics was certainly coherent given the ignorance of the basis of heredity, and was, in a sense, more nearly complete than Darwin’s precisely because it included and depended on a definite theory of inheritance. A direct challenge to Darwin appeared in 1860 in an article in the prestigious journal Edinburgh Review, Although unsigned, it is generally accepted that its author was Richard Owen, a zoologist of considerable fame and prestige whose Hunterian Lectures on zoology were attended by Queen Victoria and Darwin himself. Exhibiting a typical hardworking professional’s disdain for the amateur, Owen writes that Darwin

has long been favourably known…by the charming style [of his] observations…. Of independent means, he has full command of his time for the prosecution of original research…. The same pleasing style which marked Mr. Darwin’s earliest work, and a certain artistic disposition…

have had the result that “several, and perhaps the majority, of our younger naturalists have been seduced into the acceptance” of his theory.4

Owen’s personal attack aside, he points out, quite correctly, that neither Darwin nor anyone else knows what the underlying phenomena of heredity and development really are and that the transformation and divergence of organisms over time might simply be the manifestation of some hidden laws of development. Moreover, similar species that Darwin would claim as having evolved from a common ancestor might simply be developmental variants produced in response to different environments. I must confess that in reading Owen’s essay I found myself over and over nodding my head in agreement. Given the state of ignorance of basic biological processes in 1860, Owen might well have been right.

How are we to explain the extraordinary activity surrounding the 150th anniversary of the appearance of On the Origin of Species ? It seems unlikely that an enthusiasm of equal magnitude will greet the 150th anniversary, seven years from now, of Mendel’s paper, if we can judge by the moderate celebrations of its one hundredth in 1966. Yet genetics in its present molecular stage pervades the public consciousness as more and more genes are discovered that may be relevant to health and longevity.

The primary reason for the attention being paid to Darwin is the rejuvenation in recent years of theories of the divine creation of the earth and the organisms that inhabit it. In the years following the end of World War II, natural science became a major preoccupation of the state and of education. The sounds of the explosions over Hiroshima and Nagasaki were heard in every American classroom and a dozen years later Sputnik had hardly made its first orbit before Congress was pouring money into the institutions of American science, both universities and government agencies like the National Science Foundation and the National Institutes of Health. One immediate consequence was the creation by the NSF of the Biological Sciences Curriculum Study in 1958, which brought together university and high school teachers to rewrite the biology curriculum for the schools.

The result was a major change in the teaching of biology, with a large emphasis on evolution both in textbooks and in the classroom. Although we may think that the Scopes trial legitimized the teaching of evolution, it had little effect on public education. When I was a high school student in the late 1940s, evolution was not part of the standard science curriculum even in the New York public high schools, although teachers were at liberty to introduce it. Sputnik changed all that.

There remains, nevertheless, a substantial population whose commitment to a fundamentalist Christian belief in divine creation of the earth and its inhabitants has driven them to political action. Having been convinced that the separation of church and state is here to stay, they have adopted a pseudo-scientific theory of intelligent design in which the designer is unspecified, and attempted to introduce it into the school curricula in the name of intellectual openness. The scientific community has the definite sense of being embattled and one of its responses is to use the two hundredth anniversary of the birth of its apostle of truth about the material basis of evolution and the 150th anniversary of the appearance of his gospel to carry on the struggle against obscurantism. Jerry Coyne’s Why Evolution Is True is intended as a weapon in that struggle.

Coyne is an evolutionary biologist who, like his former student H. Allen Orr, has been a leader in our understanding of the genetic changes that occur when species are formed. His primary object in writing this book is to present the incontrovertible evidence that evolution is a physical fact of the history of life on earth. In referring to the theory of evolution he makes it clear that we do not mean the weak sense of “theory,” an ingenious tentative mental construct that might or might not be objectively true, but the strong sense of a coherent set of true assertions about physical reality. In this he is entirely successful.

Where he is less successful, as all other commentators have been, is in his insistence that the evidence for natural selection as the driving force of evolution is of the same inferential strength as the evidence that evolution has occurred. So, for example, he gives the game away by writing that when we examine a sequence of changes in the fossil record, we can

determine whether the sequences of changes at least conform to a step-by-step adaptive process. And in every case, we can find at least a feasible Darwinian explanation.

But to say that some example is not falsification of a theory because we can always “find” (invent) a feasible explanation says more about the flexibility of the theory and the ingenuity of its supporters than it says about physical nature. Indeed in his later discussion of theories of behavioral evolution he becomes appropriately skeptical when he writes that

imaginative reconstructions of how things might have evolved are not science; they are stories.

While this is a perfectly good argument against those who claim that there are things that are so complex that evolutionary biology cannot explain them, it allows evolutionary “theory” to fall back into the category of being reasonable but not an incontrovertible material fact.

There is, of course, nothing that Coyne can do about the situation. There are different modes of “knowing,” and we “know” that evolution has, in fact, occurred in a stronger sense than we “know” that some sequence of evolutionary change has been the result of natural selection. Despite these misgivings, it is the case that Coyne’s book is the best general explication of evolution that I know of and deserves its success as a best seller.

An important property of adaptive evolution is that it is usually a slow process. Certainly there are cases where a single genetic change can mean the difference between life and death in a hostile environment. The classic cases are the mutations that give pathogenic microorganisms the ability to resist antibiotics or mutations that allow crops to resist pathogens, for example insects or herbicides. But these are not representative models for how species adapt, by accumulation of mutations of small effect, to changes in food availability, temperature modifications, and the thousand shocks that flesh is heir to. The usual small differences in fitness among genotypes are therefore manifest as detectable evolutionary change only after thousands of generations.

This deliberate tempo has presented the human species with a problem of adaptation. With a human generation of about twenty-five years, there have been roughly only one hundred generations since the founding of the Roman Republic. Yet the changes in the human environment caused by changes in human activity have been enormous. Changes in diet, habitation, working conditions, the pollution of air and water, and especially the considerable increase of lifespan that result in major alterations and breakdowns in the bodily machinery have all been too rapid for genetic adaptation.

Indeed for environmental changes that have their effect after the age of reproduction, it is not clear that natural selection can operate at all. The constant exposure to high doses of solar radiation that is experienced by surfers on the California beaches might induce an eventually fatal skin cancer, but the cancer death almost always occurs well after reproductive age, so there is no opportunity for selection to act. The general result is that parts of the human genome are out of correspondence with the conditions of modern life.

Greg Gibson, a prominent student of the human genome and of the genetics of development, brings together in It Takes a Genome typical cases of this mismatch between the human physiology that is an inheritance from the past and modern environmental challenges. As a consequence of his past work on genetics and development, Gibson does not fall into the error of that genomania that supposes that every difference between individuals is a consequence of having different genes. He is careful to insist that there be very good evidence for the conclusion that some disease conditions reveal a genetic defect.

Nevertheless he makes a good case that the current state of the human genotype makes us susceptible to physiological and developmental challenges that did not exist for our remote ancestors. The major changes from the usually minimal hunter-gatherer animal and plant diets to high-calorie sugar intakes cause great stress to our carbohydrate metabolism. In a curious contradiction of modern life, while in many human populations, for example in Africa, people are dying young from overwork and undernourishment, people in technologically advanced societies are dying at a greater age from overeating and too little physical activity. We cannot count on natural selection to deal with the problem.

It seems that Cleopatra’s is not the only nose in question. In his brief Autobiography Darwin writes of his successful visit to Captain FitzRoy to arrange for his trip on the Beagle :

Afterwards, on becoming very intimate with Fitz-Roy, I heard that I had run a very narrow risk of being rejected on account of the shape of my nose! He was an ardent disciple of Lavater, and was convinced that he could judge of a man’s character by the outline of his features; and he doubted that anyone with my nose should possess sufficient energy and determination for the voyage. But I think he was afterwards well satisfied that my nose had spoken falsely.

But what if it had been bigger?

  1. 1

    Le nez de Cléopâtre, s’il eût été plus court, toute la face de la terre aurait changé,” See Pensées (Paris: Gallimard, 1977), fragment 392, p. 243.

  2. 2

    Science, Technology and Society in Seventeenth-Century England (H. Fertig, 1938).

  3. 3

    I am indebted to Janet Browne for telling me about the circulating library.

  4. 4

    The Edinburgh Review, April 1860.

  • Email
  • Print