by Ted Nield
Darwin’s theory of evolution by natural selection, however, is often referred to in the twin names of Darwin and Wallace, to give credit to Alfred Russel Wallace, who sketched the same idea (and, crucially, the driving mechanism) in February 1858, the year before Darwin published The Origin of Species. Wallace was seized by the same idea as Darwin while recovering from a malarial attack in a beach hut at Dodinga, on the almost unexplored island of Gololo (Halmahera) in the Moluccas. The enforced rest gave him the respite from collecting that he needed for more theoretical thoughts. Darwin, meanwhile, had been most of the time at home in Kent since returning to England from the Beagle voyage, wrestling with natural selection, and how to present it to the world, for the best part of two decades.
Scientists usually mean nothing but well by seeking to honour their heroes, yet this will to elect them to the pantheon of the gods so often embroils everyone in acrimonious, futile disputes that an impartial observer may reasonably wonder why the habit persists. As we shall have more to say about the chemical elements later, let us take this example from the world of chemistry, where there is no greater honour than to have one of them named after you.
Elemental forces
In 1997 a long-running and acrimonious dispute over the naming of the element seaborgium (atomic number 106) came to an end. It was the first time an element had been named for a living scientist (Nobel Prize-winner Glenn T. Seaborg, co-discoverer of plutonium). The naming of elements and other chemical substances is the job of a body called the International Union of Pure and Applied Chemistry (IUPAC), of which all national chemical societies around the world are members. Each member state pays its dues according to a complex formula, and the nation that paid most to IUPAC was the USA. It was from this quarter that pressure to name element 106 after Glenn Seaborg, Professor of Chemistry at the University of California at Berkeley, principally came.
The US lobby held that a venerable IUPAC rule banning the naming of elements after living scientists had already been broken in the case of einsteinium (element 99), discovered in 1952 in the debris of the thermonuclear explosion at Eniwetok Atoll. It is probably true that IUPAC would have fallen over itself to name an element after ‘the world’s greatest scientist’, rules or no rules. However, as IUPAC pointed out, the finding was not published until 1955, by which time the great sage had died. So there was no precedent.
Considering the case for ‘seaborgium’ dismissed, IUPAC proposed that element 106 be named for Ernest Rutherford. Rutherford was the New Zealander who (with others) worked out the structure of the atom and the nature of the various radioactive emissions and who was also the first to realize that radioactive decay could be used to determine the age of the Earth. But the Americans kept up their pressure.
In the end, by virtue of its enormous financial clout, the USA got its way over element 106, which officially became seaborgium in 1997 and Seaborg lived a further two years to savour the crowning triumph of his career.
If naming things can cause such problems, it is easy to imagine the difficulties associated with the attribution of ideas. Almost every idea has occurred before to someone else, and often long ago, when nobody realized how important it was (like the mapmaker Ortelius and continental drift). To take another example: geology’s central doctrine of uniformitarianism, which allows geologists to interpret the past by reference to the processes going on around us today, is usually said to have arisen in the late eighteenth century with the Scots geologist James Hutton. However, it could be said to have been around since at least 55 BC, when the philosopher-poet Lucretius wrote: ‘the movement of atoms today is no different from what it was in bygone ages, and always will be. Things that have regularly come into being will continue to come into being in the same manner; they will be and grow and flourish so far as each is allowed by the laws of nature.’
And as for atoms, they go back all the way to Epicurus (341–270 BC), whose school helped lay the intellectual foundations for modern science. If you read original sources, you soon discover that in fact nearly all science’s relevant ideas have been there right from the beginning, like jigsaw pieces waiting for someone to see where they fit.
As we shall see, geologists soon came to grasp the idea of supercontinents older than Pangaea, ones that broke up and re-formed, again and again, deep in Earth history. Finding a scientist after whom to name the Supercontinent Cycle shows how hard it is to single out individuals for honours in science’s cooperative venture. We shall attempt the choice from three men, in reverse chronological order of their entry into the story: John Tuzo Wilson, John Sutton and John Joly.
New under the sun
All through van der Gracht’s volume of proceedings from his New York symposium, Wegener’s critics make one point constantly. If ‘a Pangaea’ really had existed, why did it wait so long before breaking up? Rollin T. Chamberlin of the University of Chicago asked: ‘What was happening throughout most of geological time? Why did the continents remain coalesced only to become fragmented very recently?’ David White of the US National Research Council agreed: ‘How could it happen that conditions favouring the sliding of the continents to the four corners of the earth did not come about until, geologically speaking, almost yesterday?’ Joseph Singewald of Johns Hopkins University pointed out: ‘The forces called upon by Wegener were operative in pre-Carboniferous time, as in post-Carboniferous time.’ Why then should they only have become effective right at the end of our planet’s long life story?
In his lengthy summing-up, the symposium’s convener nailed this point right away. There was a logical flaw in the argument, he said. Wegener did not talk about any continental drift that may have happened before Pangaea formed because ‘the relevant facts are too little known’. It was not legitimate to infer that continental drift had not operated before Pangaea just because the theory’s author had not chosen to address the issue.
Touché … But what may have begun as the response of a quick-witted lawyer on behalf of his absent client soon took on the form of a crucial scientific idea, another truly wild surmise. Perhaps supercontinents were indeed, like so much else in nature, cyclic. Even in van der Gracht’s symposium, one of the very earliest records of a public discussion of drift theory, geologists were hinting at previous phases of continental drift before Pangaea. Wegener’s book had set out the story of only the most recent episode in a process that perhaps stretched back into the depths of geological time. Drift did not need to be a mysterious one-off, incompatible with uniformitarianism and endlessly repeating histories.
The benign cyclone and the unclassified residuum
Let us return for a moment to the carpenter’s bench, and the way the lasagne that was squeezed in the vice to create the mountain range we called the Lasagnides stuck partly to both jaws when the vice was reopened. What would happen next? The answer of course is that new sediments will accumulate in the gap of the open vice (perhaps, on this occasion, a helping of melanzane parmigiana), which then become squeezed in turn to create a new range of mountains, the Melanzanides, sitting in roughly the same orientation as its predecessors.
The spatial coincidence of old and new mountain ranges, noted by Swiss geologist Emile Argand as early as 1824, is readily explained in modern, plate-tectonic terms of continental blocks splitting apart again along the sutures that were created when they last collided. And so it was that, as the era of plate tectonics was just dawning, the cyclic nature of continental rifting, oceanic expansion, followed by subduction and contraction and finally collision and mountain building, was explained by one of the greatest geologists of the twentieth (and perhaps of any) century, the ‘benign cyclone’, John Tuzo Wilson (1908–93) of the University of Toronto.
In some Huguenot history of geology, pride of place would have to be conceded to Alex du Toit, but ‘Tuzo’would run him a close second. He was born in Ottawa to John Wilson, a Scottish engineer, and an adventurous mountaineering woman called Henrietta Tuzo, whose ancestors had crossed the Atlantic and land
ed in Virginia at about the same time as du Toit’s people had been heading south.
Tuzo was one of those charismatic, larger-than-life people whose entry into a room caused heads to turn and conversations to stop. Your eyes went to him; you felt your spirits lifting. His school in Ottawa had made him head boy, and he kept the position for the rest of his life. With his resonant voice he compelled your attention and persuaded you – often against your will – that he was not only right about this but also pretty much right about everything (which, by and large, he was). A positive man, not given to regrets, he would have been brilliant, you felt, at whatever career he had followed, especially, perhaps, politics; and as though to show off his wide-ranging facility, he was also a published expert on antique Chinese porcelain. But global tectonics was his passion, and the plate-tectonic revolution was made for him. It was also very largely made by him.
Tuzo had not always been right. Originally a devotee of the contracting-Earth hypothesis, he became a convert to drift as he was entering his fifties (by which time he had been Professor of Geophysics at the University of Toronto for a decade). Swiftly recanting his former views, Tuzo saw the way the Earth’s mountain belts were often superimposed upon one another, and set about explaining it in terms of plate tectonics. In a classic paper published in Nature in 1966 and titled ‘Did the Atlantic close and then re-open?’ he addressed the coincidence of the modern Atlantic with two mountain ranges called the Caledonides in Europe and the Appalachians in the USA. It was the very first time the new plate tectonics had been extended back to the pre-Pangaean Earth.
These two mountain ranges are really one and the same – except that they are now separated by the Atlantic Ocean, which cut the range in two at a low angle when it opened between them. At one time the two belts had been joined, end to end, Caledonides in the north, Appalachians in the south; and the collision that had created them was one event among many that built the supercontinent Pangaea. Indeed, the matching of the now separated halves of this once-mighty chain provided Wegener with one of his key ‘proofs’ – part of his geological matching of opposing Atlantic shores.
As van der Gracht pointed out on his behalf, Wegener did not speculate about how his Pangaea had come together. But as the new plate tectonics emerged from studies of the ocean floor and began to revitalize drift theory, the time was ripe to see the break-up of Pangaea as part of a bigger process. Professor Kevin Burke of the University of Houston, Texas, recalls that on 12 April 1968 in Philadelphia, at a meeting titled ‘Gondwanaland Revisited’ at the Philadelphia Academy of Sciences, Wilson told his audience how a map of the world showed you oceans opening in some places and closing in others. Burke recalls: ‘He therefore suggested that, because the ocean basins make up the largest areas on the Earth’s surface, it would be appropriate to interpret Earth history in terms of the life cycles of the opening and closing of the ocean basins … In effect he said: for times before the present oceans existed, we cannot do plate tectonics. Instead, we must consider the life cycles of the ocean basins.’ This key insight had by then already provided Wilson with the answer to an abiding puzzle in the rocks from either side of the modern Atlantic.
Nothing pleased Tuzo more than a grand, overarching framework that made sense of those awkward facts that get thrown aside because they don’t fit – ideas that philosopher William James dubbed the ‘unclassified residuum’. Geologists had been aware since 1889 that within the rocks forming the Caledonian and Appalachian mountains – that is, rocks dating from the early Cambrian to about the middle Ordovician (from 542 to 470 million years ago) – were fossils that fell into two clearly different groups or ‘assemblages’. This was especially true for fossils of those animals that in life never travelled far, but lived fixed to, or grubbing around in, the seabed. By analogy with modern zoology, the two assemblages represented two different faunal realms, just like those first described on the modern Earth by Philip Lutley Sclater and Alfred Russel Wallace.
These two ancient realms were found to broadly parallel the shores of the modern Atlantic Ocean and were described by Charles Doolittle Walcott (1850–1927). Walcott, who had received little formal education, rose to become Director of the US Geological Survey in 1894 and was perhaps one of the most industrious people ever to do and administer science in the United States. He named these assemblages the ‘Pacific’ and ‘Atlantic’ provinces; rocks in North America containing the Pacific assemblage, and rocks of the same age in Europe containing the Atlantic.
Had this split been perfect it would have raised no eyebrows among continental fixists because the division would have been easily explained by the present arrangement of continents and oceans. Unfortunately there were some distinctly awkward exceptions to the rule. In some places in Europe, such as the north of Scotland, geologists found rocks with typical ‘American’ fossils in them, while in some places in North America rocks turned up containing typical European species. In an echo of one of the two scenarios that puzzled Victorian biogeographers, things were being found close together that should, by their differences, have been far apart; but with the added twist that, by and large, they usually were far apart.
This conundrum could be explained, Wilson reasoned, if the present Atlantic Ocean was not the first to have separated its opposing shores: if there had been an older Atlantic, which had closed and then reopened to form the modern one. According to his idea, the old Caledonian–Appalachian mountain chain had formed as the vice shut for the first time, eliminating a now long-vanished ocean that Wilson called the ‘proto-Atlantic’. But when this suture had reopened, more or less (but not perfectly) along the same line, some of the rocks squeezed between the forelands had stuck to the opposite jaw of the vice, stranding some American fossils on the European side and vice versa. The fossil distributions were saying that there had been continental drift before Pangaea. Moreover, if this particular example could be extended into a general rule, mountain building itself was inherently cyclic. This process, involving the repeated opening and closing of oceans along ancient lines of suture, has since come to be known as the Wilson Cycle, a term first used in print in 1974 in a paper by Kevin Burke and the British geologist John Dewey.
Wilson did not address another interesting problem, which was the question of exactly where on the Earth all this pre-Pangaean action had played out. From the geological evidence it was clear which continental blocks had done the colliding: which had acted as the jaws of the vice. But where had they been on the globe at that time?
Wilson did not address this issue because (as van der Gracht might have said) the relevant facts were too little known. They were not long in coming. It soon turned out that Wilson’s ‘proto-Atlantic’ had in fact been sitting right at the bottom of the world. Before ‘our’ Atlantic had opened, the two jaws of the vice (now represented by North America and Eurasia) had not only opened and closed (and thus helped build Pangaea) but had since migrated north together as far as the Tropic of Cancer before deciding to reopen hundreds of millions of years later, in the great Pangaean split-up.
Wilson’s name for this ancient vanished ocean, the ‘proto-Atlantic’, soon came to seem inappropriate, particularly since the same name was coming to be used for the early stages of the formation of the modern Atlantic. Wilson’s ocean had been squeezed out of existence by about 400 million years ago: 200 million years before the present Atlantic had even begun to form within Pangaea; so it was no true ‘proto-Atlantic’ in any real sense. Therefore, in 1972, Wilson’s Ocean was renamed Iapetus, which maintains a shadow of the Atlantic link, since in Greek myth Iapetus, son of Earth (Ge) and Heaven (Uranos), was brother to Tethys and Okeanos, and father of the Titan, Atlas.
However, Wilson’s great idea was a crucial step forward. It reopened the whole question of ‘what happened before Pangaea?’ By suggesting that his ‘proto-Atlantic’ had opened within an earlier supercontinent (just as the modern Atlantic did within Pangaea) he also linked his process to a grander cycle leading from
one supercontinent Earth to another.
Wilson’s originality consisted chiefly of being among the first to consider pre-Pangaean plate tectonics; but it would be stretching things a little to name the whole Supercontinent Cycle after him because his model refers only to ‘introversion’: the opening and closing of an ‘interior ocean’, one which opens within a fragmenting supercontinent. And that, as we have seen, is only one way a supercontinent can re-form.
Sutton’s seed
In 1919 the Sutton’s Seeds dynasty was blessed with a son. Unfortunately for this British business, which still flourishes today, it would have to do without the drive and determination of John Sutton (1919–92), who would instead devote his talents to the study of the oldest rocks on Earth. He would eventually join the long line of charismatic leaders of Imperial College London’s Royal School of Mines, including Thomas Henry Huxley and Sutton’s predecessor, Herbert H. Read. He would also marry his near contemporary, Janet Vida Watson (1923–85), to forge perhaps the most formidable husband-and-wife team in geological history.
It was not always easy to work with the great Professor, who suffered from sudden fits of incandescent rage. As his obituarist Professor Dick Selley recalls: ‘To be one of his students was like living on the slopes of a volcano. The soil was fertile, the view awe-inspiring, but long periods of productive calm could suddenly be punctuated by an eruption.’ Collaborating on almost everything, Watson and Sutton together pioneered the study of the ancient, complex rocks of the Precambrian, but their aim was clearly summed up in the title of a lecture Sutton gave in 1967, ‘The extension of the geological record into the Precambrian’. Their aim was to learn how to extend the familiar picture of vanished oceans and the mountain ranges that grew up in their place, back into that mysterious age.