OU Lecture 2009: Solving the riddle
Random chance, design or cumulative natural selection? Dawkins explores how Darwin and...
Random chance, design or cumulative natural selection? Dawkins explores how Darwin and his peers solved the riddle of life.
- Duration: 10 mins
- Published on: Monday 6th April 2009
- Introductory Level
- Posted under: Natural History
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Was Darwin the most revolutionary scientist ever? If by revolutionary we mean the scientist whose discovery initiated the most seismic overturning of pre-existing science, the honour would at least be contested by Newton, Einstein and the architects of Quantum Theory. Those same physicists might have outclassed Darwin in sheer intellectual fire-power but Darwin probably did revolutionise the world view of people outside science more comprehensively than any other scientist. He may be only one plausible candidate for the most important or most revolutionary scientist ever, but Darwin has a strong claim to be the most seditious.
Before Darwin it took a philosopher of the calibre of David Hume to rumble the illogic of if a thing looks designed it must have been designed. And even Hume, though he could see that the argument to design was a bad argument, couldn’t think of a good alternative. Darwin provided the alternative. How Hume would have relished the ‘I told you so’ moment that Darwin handed him. The argument to design was familiar to Darwin, for whose cohort of Cambridge Undergraduates the Reverend William Paley was compulsory reading. If it looks designed it was designed, and the more designed it looks the stronger the argument.
Looks designed means something along the lines of statistically improbable in a previously specified direction. Paley’s famous watch and the vertebrate eye are both statistically improbable, in that if you take their parts and scramble them into random combinations a million times not once will you hit upon a combination that tells the time to the nearest second or that sees in full colour stereoscopically and with instantaneous light metering and auto-focus. We have to add in a previously specified direction because with hindsight every random combination can be made to seem as improbable as any other.
How astounding that of all the blades of grass on the golf course the ball landed on this particular blade and no other. The reason a hole-in-one is so rare is that the hole is specified in advance as the target. If you specified any particular blade of grass in advance and the ball landed on it, it would be as remarkable as a hole-in-one. Actually more so because the hole is larger than a blade of grass. Watches and eyes have their functions, telling the time and seeing respectively, specified in advance, and both are functions that are difficult to achieve.
So a random scrambling of parts is exceedingly unlikely to perform either function with any efficiency. The fact that a watch does tell the time accurately, and with at least two hands to accommodate two conveniently related timescales, correctly indicates to any reasonable person that it is not the product of random chance. Before Darwin the only known alternative to random chance was design. Everybody could intuitively see the force of the argument that Paley generalised from watch to eye, and to every other part of every living body. There must have been a designer. And yet intuition was wrong. It’s the unholy juxtaposition of commonsensically true with now known to be false that singles out Darwin’s great idea as seditious.
Darwin discovered the alternative to chance and design that had eluded everybody, even Hume. The answer is cumulative natural selection. Provided that a smoothly cumulative gradient of improvement exists, not a difficult condition to realise, natural selection is likely to find it and will propel evolution up the slopes of mount improbable to apparently limitless heights of perfection which, if you overlook the smooth cumulative gradients, you would think were too improbable to countenance.
Darwin’s dangerous idea was seditious, revolutionary, deeply surprising and yet, having eluded Hume in the 18th Century and every great philosopher and scientist before him, it was an idea that came independently into the prepared minds of at least two naturalists in the 19th Century, Charles Darwin and Alfred Russel Wallace. I’m not talking about evolution itself for that idea had occurred to many, including Lamarck and Darwin’s Grandfather Erasmus. Nor am I talking about natural selection itself for that too, as we shall see, had crossed other minds than Darwin’s and Wallace’s. I’m talking about the idea that natural selection is powerful enough to drive evolution in such a way as to explain everything about life, including that illusion of design that, in Hume’s own words, ravishes into admiration all men who have ever contemplated them.
I singled out Darwin and Wallace as the two 19th Century naturalists who independently solved the riddle of life, but claims of priority have been made on behalf of at least two other 19th Century writers; Patrick Matthew and Edward Blyth. If those claims are upheld, it should be a matter of some national pride that all four independent discoverers of natural selection were British. But should they be upheld?
Edward Blyth, 1810-73, was Darwin’s near contemporary. Like Darwin and Wallace he was a naturalist and collector of specimens in the tropics, in his case India. He really did hit upon the idea of natural selection, publishing it in 1835, but his version is only what we would today call stabilising selection, that is natural selection preserving the original type, not natural selection driving evolutionary change to ever new types. No wonder Blyth was a staunch creationist, he thought of natural selection as preserving God’s original creations in their pristine archetypal state. He was the very opposite of an evolutionist. Natural selection in his formulation would amount of a force of resistance against evolutionary change.
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’.
When The Origin of Species was first published, Matthew protested at Darwin’s failure to cite him, and Darwin punctiliously did so in later editions of his book. The passage that immediately follows the sentence I just quoted seems to bear out Darwin’s acknowledgement that Matthew clearly saw the full force of the principle of natural selection. Like Blyth, indeed Darwin seems to have been indebted to Blyth’s observations, Matthew saw the importance of over-production and the consequent struggle for existence.
“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 thousand-fold, 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, their standard of perfection and fitness to continue their kind by reproduction.”
Well, I’m still 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 naval timber? 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 12th 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 seems to have had 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 said, “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 everything about life?
As a fair parallel, imagine that a 17th Century ancestor of Patrick Matthew saw an apple fall, perhaps in the very same orchard where the Matthews had been farming in the Carse of Gowrie since the 16th 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.