Seeing Further (23 page)
Authors: Bill Bryson
Patrick Matthew (1790–1874) used his experience of growing apple and pear trees in his Scottish orchard to write a book, in 1831, on
Naval Timber and Arboriculture.
In an appendix to this work, Matthew recognised that the principles of artificial selection, which he advocated for growing good quality timber for the navy, could be generalised to natural selection. Unlike Blyth, Matthew didn’t see natural selection purely as a stabilising force, preserving the original form of the species. He even went so far as to speculate that:
… the progeny of the same parents, under great differences of circumstance, might, in several generations, even become distinct species, incapable of co-reproduction.
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When
The Origin of Species
was first published, Matthew protested at Darwin’s failure to cite him, and Darwin punctiliously did so in the third (1861) and subsequent editions of his book. The passage that immediately follows the above-quoted sentence seems to bear out Darwin’s acknowledgment that Matthew ‘clearly saw the full force of the principle of natural selection’:
The self-regulating adaptive disposition of organised life may, in part, be traced to the extreme fecundity of Nature, who, as before stated, has, in all the varieties of her offspring, a prolific power much beyond (in many cases a thousandfold) what is necessary to fill up
the vacancies caused by senile decay. As the field of existence is limited and preoccupied, it is only the hardier, more robust, better suited to circumstance individuals, who are able to struggle forward to maturity, these inhabiting only the situations to which they have superior adaptation and greater power of occupancy than any other kind; the weaker, less circumstance-suited, being prematurely destroyed. This principle is in constant action, it regulates the colour, the figure, the capacities, and instincts; those individuals of each species, whose colour and covering are best suited to concealment or protection from enemies, or defence from vicissitude and inclemencies of climate, whose figure is best accommodated to health, strength, defence, and support; whose capacities and instincts can best regulate the physical energies to self-advantage according to circumstances – in such immense waste of primary and youthful life, those only come forward to maturity from the strict ordeal by which Nature tests their adaptation to her standard of perfection and fitness to continue their kind by reproduction.
Like Blyth (indeed, Darwin seems to have been indebted to Blyth’s observations on the subject), Matthew saw the importance of overproduction and the consequent struggle for existence, and he clearly went further than Blyth.
But I am left wondering. Did Matthew really grasp the immense power of the discovery that he had made? Did he appreciate that natural selection is the answer to the great riddle of existence? Did he see it as the explanation for all of life, the destroyer of the argument from design? If he had, wouldn’t he have published it in a more prominent place than the appendix to a manual on silviculture? Wouldn’t he have trumpeted it from the rooftops, as arguably the most important idea anyone ever had? On the contrary, Matthew seems to have found the idea so obvious – almost trivial – as to need no discovery! In a letter to the
Gardeners’ Chronicle
of 12 May 1860, he wrote:
To me, the conception of this law of Nature came intuitively as a self-evident fact, almost without an effort of concentrated thought. Mr Darwin here seems to have more merit in the discovery than I have had – to me it did not appear a discovery. He seems to have worked it out by inductive reason, slowly and with due caution to have made his way synthetically from fact to fact onwards; while with me it was by a general glance at the scheme of Nature that I estimated this select production of species as an a priori recognisable fact – an axiom, requiring only to be pointed out to be admitted by unprejudiced minds of sufficient grasp.
With hindsight, we may be tempted to sympathise. But where Huxley, on closing
The Origin,
movingly sighed, ‘How extremely stupid of me not to have thought of that’, Matthew’s response would seem to have been the Victorian equivalent of ‘Big deal. So what else is new?’ Is this the response of a man who, seven years before Darwin and twenty-seven before Wallace, found himself in possession of the central, unifying idea that dominates all biology and explains almost everything about life?
As a fair parallel, imagine that a seventeenth-century ancestor of Patrick Matthew saw an apple fall (perhaps in the very same orchard, for the Matthews had been farming in the Carse of Gowrie since the sixteenth century). Our earlier Matthew, I imagine to have been a physicist and, as he watched his apple fall, he conjectured that the Earth exerted an attractive force on apples, pulling them towards it. If this hypothetical horticulturalist had later written to Isaac Newton and indignantly claimed priority for the theory of gravitation, Newton (a less generous man than Darwin) would rightly have given him short shrift. The physicist Matthew, let’s suppose, confined his theory to apples, or at best to objects falling towards the Earth. He lacked Newton’s grand vision of the same force acting throughout the universe, responsible for the elliptical orbits of the planets, for the stars in their courses, ultimately for the very structure of the universe itself.
I agree with W.J. Dempster, Patrick Matthew’s modern champion, that Matthew has been unkindly treated by history.
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‘But, unlike Dempster, I hesitate to assign full priority to him. Partly, it is because he wrote in a much more obscure style than either Darwin or Wallace, which makes it hard to know in some places what he was trying to say (Darwin himself noted this). But mostly it is because he seems to have underestimated the idea, to an extent where we have to doubt whether he really understood how important it was. The same could be said, even more strongly (which is why I have not treated his case in the same detail as Matthew’s), of W.C. Wells, whom Darwin also scrupulously acknowledged (in the fourth and subsequent editions of
The Origin).
Wells made the leap to generalise from artificial to natural selection, but he applied it only to humans, and he thought of it as choosing among
races
of people rather than individuals as Darwin and Wallace did. Wells therefore seems to have arrived at a form of ‘group selection’ rather than true, Darwinian natural selection as Matthew did, which selects individual organisms for their reproductive success. Darwin also lists other partial predecessors, who had shadowy inklings of natural selection. Like Patrick Matthew, none of them seems to have grasped the earth-shattering
significance
of the idea they had lit upon, and I shall use Matthew’s name to represent them all. I am increasingly inclined to agree with Matthew that natural selection itself scarcely needed discovering. What needed discovering was the significance of natural selection for the evolution of all life.
Alfred Russel Wallace (1823–1913) was different. Although he discovered natural selection after Matthew (and after Darwin’s unpublished manuscripts) he has a genuine claim to be up there with Darwin and Newton, among the immortals.
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When Wallace hit upon natural selection, he was in no doubt of its immense importance for the whole history of life. The very title of his paper – the one he sent to Darwin, and which set the cat among Darwin’s pigeons – says it all:
On the Tendency of Varieties to Depart Indefinitely from the Original Type.
‘Depart indefinitely’, that was the key phrase. If they depart indefinitely from the original type, they can branch and eventually spawn all of life. And Wallace made that explicit in his paper.
The drama of how Wallace’s letter arrived at Down House on 17 June 1858, casting Darwin into an agony of indecision and worry, is too well known for me to retell it. In my view the whole episode is one of the more creditable and agreeable in the history of scientific priority disputes – precisely because it wasn’t a dispute – although it so easily could have become one. It was resolved amicably, and with heartwarming generosity on both sides, especially Wallace’s. As Darwin later wrote:
Early in 1856 Lyell advised me to write out my views pretty fully, and I began at once to do so on a scale three or four times as extensive
as that which was afterwards followed in my
Origin of Species;
yet it was only an abstract of the materials which I had collected, and I got through about half the work on this scale. But my plans were overthrown, for early in the summer of 1858 Mr Wallace, who was then in the Malay archipelago, sent me an essay ‘On the Tendency of Varieties to depart indefinitely from the Original Type’; and this essay contained exactly the same theory as mine. Mr Wallace expressed the wish that if I thought well of his essay, I should send it to Lyell for perusal.
The circumstances under which I consented at the request of Lyell and Hooker to allow of an extract from my MS., together with a letter to Asa Gray, dated September 5, 1857, to be published at the same time with Wallace’s Essay, are given in the
Journal of the Proceedings of the Linnean Society,
1858, p. 45. I was at first very unwilling to consent, as I thought Mr Wallace might consider my doing so unjustifiable, for I did not then know how generous and noble was his disposition. The extract from my MS. and the letter to Asa Gray … had neither been intended for publication, and were badly written. Mr Wallace’s essay, on the other hand, was admirably expressed and quite clear. Nevertheless our joint productions excited very little attention, and the only published notice of them which I can remember was by Professor Haughton of Dublin, whose verdict was that all that was new in them was false, and what was true was old. This shows how necessary it is that any new view should be explained at considerable length in order to arouse public attention.
Darwin was over-modest about his own two papers. Both are models of the explainer’s art. Wallace’s paper is also very clearly argued. His ideas were, indeed, remarkably similar to Darwin’s, and there is no doubt that Wallace arrived at them independently. In my opinion the Wallace paper needs to be read in conjunction with his earlier paper in the
Annals and Magazine of
Natural History.
Darwin read this paper when it came out in 1855. Indeed, it led to Wallace joining his large circle of correspondents, and to his engaging Wallace’s services as a collector. But, oddly, Darwin did not see in the 1855 paper any warning that Wallace was by then a convinced evolutionist of a very Darwinian stamp. I mean as opposed to the Lamarckian view of evolution, which saw modern species as all on a ladder, changing into one another as they moved up the ladder. By contrast Wallace, in 1855, had a clear view of evolution as a branching tree, exactly like Darwin’s famous diagram, which became the only illustration in
The Origin of Species.
The 1855 paper, however, makes no mention of natural selection or the struggle for existence.
That was left to Wallace’s 1858 paper, the one that hit Darwin like a lightning bolt. Here, Wallace even used the phrase ‘Struggle for Existence’. Wallace devoted considerable attention to the exponential increase in numbers (another key Darwinian point). Wallace wrote:
The greater or less fecundity of an animal is often considered to be one of the chief causes of its abundance or scarcity; but a consideration of the facts will show us that it really has little or nothing to do with the matter. Even the least prolific of animals would increase rapidly if unchecked, whereas it is evident that the animal population of the globe must be stationary, or perhaps … decreasing.
Wallace deduced from this that ‘The numbers that die annually must be immense; and as the individual existence of each animal depends upon itself, those that die must be the weakest …’ Wallace’s peroration could have been Darwin himself writing:
The powerful retractile talons of the falcon – and the cat – tribes have not been produced or increased by the volition of those animals; but among the different varieties which occurred in the
earlier and less highly organised forms of these groups, those always survived longest which had the greatest facilities for seizing their prey. Neither did the giraffe acquire its long neck by desiring to reach the foliage of the more lofty shrubs, and constantly stretching its neck for the purpose, but because any varieties which occurred among its antitypes with a longer neck than usual at once secured a fresh range of pasture over the same ground as their shorter-necked companions, and on the first scarcity of food were thereby enabled to outlive them. Even the peculiar colours of many animals, especially insects, so closely resembling the soil or the leaves or the trunks on which they habitually reside, are explained on the same principle; for though in the course of ages varieties of many tints may have occurred, yet those races having colours best adapted to concealment from their enemies would inevitably survive the longest. We have also here an acting cause to account for that balance so often observed in nature, – a deficiency in one set of organs always being compensated by an increased development of some others – powerful wings accompanying weak feet, or great velocity making up for the absence of defensive weapons; for it has been shown that all varieties in which an unbalanced deficiency occurred could not long continue their existence. The action of this principle is exactly like that of the centrifugal governor of the steam engine, which checks and corrects any irregularities almost before they become evident.
The image of the steam governor is a powerful one which, I can’t help feeling, Darwin might have envied.
Historians of science have raised the suggestion that Wallace’s version of natural selection was not quite so Darwinian as Darwin himself believed. Wallace persistently used the word ‘variety’ as the level of entity at which natural selection acts. There was an example in the long passage
I have just quoted, and also an example of Wallace’s usage of the word ‘race’ in a similar sense. Some have suggested that Wallace, unlike Darwin, who clearly saw selection as choosing among
individuals,
was proposing what nearly all modern theorists rightly denigrate as ‘group selection’. This would be true if, by ‘varieties’ or ‘races’, Wallace meant geographically separated groups of individuals, or indeed races in the more usual sense of the word. At first I wondered myself whether Wallace meant that. But a careful reading of his paper rules it out. By ‘variety’ and ‘race’ Wallace meant what we would nowadays call ‘genetic type’, even what a modern population geneticist might mean by an allele. To Wallace in this paper, variety meant not a local race of eagles, for example, but ‘that set of individual eagles whose talons were hereditarily sharper than usual’.
