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Defining DARWIN

Prometheus Books

Chapter One

Mr. Charles Darwin, well known to us all as the author of the delightful travel book Journal of Researches into the Geology and Natural History of the Various Countries Visited by HMS Beagle (1839) (better known as The Voyage of the Beagle), has now produced an audacious work that will surely be the topic of much conversation for months if not years to come. In his newly published book, On the Origin of Species by Means of Natural Selection or the Preservation of the Favoured Races in the Struggle for Existence, to give it the full title, Mr. Darwin openly declares himself a Vestiginarian! Like the unknown author of the Vestiges of the Natural History of Creation (1844), Mr. Darwin has embraced transmutationism, what Mr. Herbert Spencer calls "evolution," and what Mr. Darwin himself calls "descent with modification." In his new book-to which we will give the abbreviated title of the Origin-Mr. Darwin openly declares that all living creatures (quick and dead) are the end results of a long process of natural development from (as he says) "one or a few forms." And although his book says little about our own species, he makes very clear at the end that we too are part of the picture. "Light will be thrown on the origin of man and of his history." Yes, indeed!

So would open a review of the Origin written shortly after the book appeared in 1859. I am writing around the 150th anniversary of the publication, and (declaring an interest) I should tell you that I am the coeditor (with the distinguished historian Robert J. Richards) of the Cambridge Companion to the "Origin of Species." So I take it without argument that as a historical work, the Origin is of great significance. Goodness, the portrait of Darwin has even replaced Charles Dickens on the back of the English ten-pound note, although rumor has it that the real reason for the shift is that Darwin had a fuller beard than Dickens and thus was less easy to forge! My aim here is to assess the Origin from today's perspective, considering its contemporary value as a work of scholarship, and in respects this is a lot less easy to do than from the perspective of, say, 1860. It would be all too easy simply to dismiss it as something irretrievably dated and to leave matters at that. Frankly, I would be worried if one could not dismiss it as dated, for that would suggest that Darwin's ideas have so little interest or value that no one has bothered to try to critique them or to take the discussion further. So remember that here I am not so much suspending critical evaluation as looking at what proved interesting and stimulating in the Origin, rather than ways to take cheap shots at the past from the present.

NATURAL SELECTION

Let us turn to the content of Darwin's book; but, as we do so, let us keep in mind something as important today as it was yesterday. Although, when he published the Origin, Darwin had been stricken for twenty years with ongoing ill health, he had nevertheless pushed himself to the very first rank of British scientists. His detailed geological studies, based on his five-year-long circumnavigation of the world in the HMS Beagle under the captaincy of Robert Fitzroy, were models of empirical inquiry. His massive detailed studies of barnacles, both living and fossil, were exemplary instances of careful and thoughtful study of the world of life. We may or may not agree with Darwin's reasoning. We must respect it and cannot ignore it. Today no less than yesterday we feel at once that we are in the hands of a master. This is not some outsider trying his hand. This is a real professional at work. We can add also that whether or not we agree with Darwin, his warm and easy style makes it exceptionally easy to follow his thinking. Few will come away confused as to the points that he is making. The charming writing of the Voyage of the Beagle is once again in evidence. Some may complain-in fact in 1860 his bitter rival, the anatomist Richard Owen, writing in the Quarterly Review did complain-that the style is too easy for a serious work of science. With this I can only disagree. Too often specialists feel that save their writing is opaque and cumbersome, they are not being serious and profound. I am not saying that (in his style) Darwin has the brilliance of Richard Dawkins in the Selfish Gene. But he is very good. Would that German metaphysicians and French deconstructivists took lessons from him.

Darwin begins by taking the reader into the world of the breeder-the farmer who wants fatter pigs and hairier sheep, the enthusiast who wants evermore-fanciful feathers on his pigeon-and he argues that this is a model for change in nature. Here, as throughout his book, Darwin is riding two horses and it is not always clear which back is mounted at any one time. From the one saddle, Darwin thinks that the changes brought about by the breeders are enough to support the changes he supposes through nature. One can almost hear the voice of the Victorian skeptic: "We confess we are not convinced of this. Who ever changes a horse into a cow?" From the other saddle, Darwin prepares the way for his mechanism of change, by showing how selection of the desired is the way that breeders bring about the changes that they effect. This is surely true, although whether selection by breeders is truly analogous to what Darwin calls "natural selection" is indeed the big question at issue. Judging from today, general opinion would be that Darwin was just scratching at the surface, but that he was scratching at the right surface. We now have massive evidence of the power of selection in artificial and semiartificial circumstances, and can change organisms so much that they are really new species, isolated from all others. It is true that we have never changed a horse into a cow, but then neither did nature. They spring from common stock.

Moving to his main mechanism, Darwin first makes reference to the deductions of the Reverend Thomas Robert Malthus, who showed how readily population numbers outstrip supplies of food and space. Here Darwin's genius glows as brightly today as it ever did. With reason, the calculations of Malthus were generally taken to show the impossibility of major change. If you feed the poor from state funds in one generation, you only have more of them in the next. There is bound to be a struggle for existence, save only people practice prudential restraint. Darwin takes the struggle as force that brings on unlimited change, for in the world of animals and plants there can be no prudential restraint, and so in the bloody battle for survival those with advantageous features will tend to succeed. Let us quote Darwin on this:

Let it be borne in mind in what an endless number of strange peculiarities our domestic productions, and, in a lesser degree, those under nature, vary; and how strong the hereditary tendency is. Under domestication, it may be truly said that the whole organisation becomes in some degree plastic. Let it be borne in mind how infinitely complex and close-fitting are the mutual relations of all organic beings to each other and to their physical conditions of life. Can it, then, be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection.

Note that he does not use the alternative phrase "survival of the fittest." This was a phrase coined by Spencer, and Darwin only added it to later editions of the Origin at the urging of Alfred Russel Wallace, the codiscoverer of natural selection.

Darwin has many most interesting things to say about natural selection, a process that he argues leads to the wonderful display of fossils in the geological record as well as the multitudinous animals and plants living today. It is still amusing that Darwin appropriates a Christian metaphor when he speaks of history as a "Tree of Life," with us all today at the outer tips of the branches. It is also worth noting in passing that Darwin's mechanism of natural selection shows roots in the Christian faith. It leads to adaptations or contrivances like the hand and the eye. In other words, it supposes that nature is not thrown together randomly but is organized and it works. In the language of the philosophers, the eye shows final cause in seeing and the hand shows final cause in grasping. Here Darwin shows the effects of his training and reading. Passages of the Origin would not be out of place in Archdeacon Paley's Natural Theology or one of the celebrated Bridgewater Treatises, a series of works that appeared in the 1830s intended, in the words of their benefactor, to demonstrate "the power, wisdom, and goodness of God, as manifested in the creation." Darwin would never agree with today's neo-Creationists, the Intelligent Design Theorists, that we need interventions from outside the course of nature to explain the adaptive complexity of organisms, but he does agree with them that adaptation is the chief feature of organic life.

Natural selection leading to adaptation is of course the first of Darwin's big contributions to evolutionary theory. Paradoxically, writing today in 2006 we are more inclined to give him credit than his contemporaries in 1859. Today, although there are still doubters about the ubiquity of natural selection-for instance, the late Stephen Jay Gould-general opinion among professional evolutionists is that Darwin got it right. The chief feature of the organic world is its adaptive or organized complexity (as the late John Maynard Smith used to call it) and natural selection is the only mechanism that speaks to this. (Darwin had a secondary mechanism of sexual selection that is also involved, although some simply subsume it beneath natural selection.) Darwin in the Origin does not offer much direct evidence, and today again this is a place where time has moved on. We now have massive evidence of the workings of selection in nature. Very well known are the studies done in the 1950s by H. B. D. Kettlewell on industrial melanism in butterflies, and the studies for the past thirty years by Peter Grant and Peter and Rosemary Grant in the Galapagos Archipelago on Darwin's Finches. But they are just the tip of a huge iceberg. Of great practical importance is the fact that there has never been a medicine introduced that did not become ineffective in its original state because of the rapid, selection-fueled evolution of the attacking microorganisms.

THE CONSILIENCE

The second part of the Origin, by far the bigger section, is Darwin's second great contribution to evolutionary theory, and it, too, is as significant today as it ever was. This part is given to a review of biological discussions in different fields in the light of the mechanism of natural selection. The approach taken here, namely, using descent through natural selection to explain phenomena and in turn using the explanations to support descent through natural selection, is not Darwin's own invention. It is the method of scientific argumentation championed by William Whewell in his Philosophy of the Inductive Sciences. Whewell referred to this as a "Consilience of Inductions." Just like Newton before him and the geologists establishing plate tectonics after him, Darwin did a terrific and still powerful job of promoting a consilience. Paradoxically and rather sadly, Whewell was so opposed to what he thought were the irreligious aspects of Darwin's theory that, in his position of Master of Trinity College Cambridge, he refused to allow the Origin on the college library's shelves.

With superb confidence, which time has only burnished, Darwin takes us through the branches of his subject-instinct, paleontology, the geographical distributions of organisms on the globe, classification, morphology, embryology, and much, much more. It is hard to pick out one topic rather than another, but geography deserves special praise. Why, Darwin asks, are the inhabitants of islands off the coast of Africa similar although not identical to the inhabitants of Africa? Why are they not like the inhabitants of South America? Why conversely are the inhabitants of islands off the coast of South America-including the well-known Galapagos Archipelago-like the inhabitants of South America and not like the inhabitants of Africa? Can there be any explanation except descent with modification?

The most striking and important fact for us in regard to the inhabitants of islands, is their affinity to those of the nearest mainland, without being actually the same species. Numerous instances could be given of this fact. I will give only one, that of the Galapagos Archipelago, situated under the equator, between 500 and 600 miles from the shores of South America. Here almost every product of the land and water bears the unmistakeable stamp of the American continent. There are twenty-six land birds, and twenty-five of those are ranked by Mr Gould as distinct species, supposed to have been created here; yet the close affinity of most of these birds to American species in every character, in their habits, gestures, and tones of voice, was manifest. So it is with the other animals, and with nearly all the plants, as shown by Dr. Hooker in his admirable memoir on the Flora of this archipelago. The naturalist, looking at the inhabitants of these volcanic islands in the Pacific, distant several hundred miles from the continent, yet feels that he is standing on American land. Why should this be so? Why should the species which are supposed to have been created in the Galapagos Archipelago, and nowhere else, bear so plain a stamp of affinity to those created in America? There is nothing in the conditions of life, in the geological nature of the islands, in their height or climate, or in the proportions in which the several classes are associated together, which resembles closely the conditions of the South American coast: in fact there is a considerable dissimilarity in all these respects. On the other hand, there is a considerable degree of resemblance in the volcanic nature of the soil, in climate, height, and size of the islands, between the Galapagos and Cape de Verde Archipelagos: but what an entire and absolute difference in their inhabitants! The inhabitants of the Cape de Verde Islands are related to those of Africa, like those of the Galapagos to America. I believe this grand fact can receive no sort of explanation on the ordinary view of independent creation; whereas on the view here maintained, it is obvious that the Galapagos Islands would be likely to receive colonists, whether by occasional means of transport or by formerly continuous land, from America; and the Cape de Verde Islands from Africa; and that such colonists would be liable to modifications; the principle of inheritance still betraying their original birthplace.

This explanation is as vital and good today as it was in 1859.

Again, to take a topic much discussed in 1859 by the anatomists and still discussed today by anatomists, why do the forelimbs of animals show similarities-what Richard Owen (1848) called "homologies"-when they are used for different ends? "What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions?" Replies Darwin: "The explanation is manifest on the theory of the natural selection of successive slight modifications, each modification being profitable in some way to the modified form, but often affecting by correlation of growth other parts of the organisation. In changes of this nature, there will be little or no tendency to modify the original pattern, or to transpose parts" (p. 434).

(Continues...)

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Excerpted from Defining DARWIN by MICHAEL RUSE Copyright © 2009 by Michael Ruse. Excerpted by permission.
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