What this means, if you think about it, is that the straight run of the dance itself rotates like the hour hand of a normal clock (though at half the speed). But anticlockwise (in the Northern Hemisphere), like the shadow on a sundial. If you were von Frisch, wouldn’t you have died happy, to have made such a discovery?
Even after clocks were invented, sundials remained essential for setting clocks and keeping them synchronized with the great clock in the sky. Hilaire Belloc’s famous rhyme is, therefore, rather unfair:
I am a sundial, and I make a botch
Of what is done far better by a watch.
It is less well-known that Belloc wrote a whole series of verses on sundials, some humorous, some sombre, more in keeping with the ‘Fighting Time’ theme of our exhibition:
How slow the Shadow creeps: but when ’tis past
How fast the Shadows fall. How fast! How fast!
Creep, shadow, creep: my ageing hours tell.
I cannot stop you, so you may as well.
Stealthy the silent hours advance, and still;
And each may wound you, and the last shall kill.
Save on the rare occasions when the Sun
Is shining, I am only here for fun.
I am a sundial, turned the wrong way round.
I cost my foolish mistress fifty pound.
You may think of this last verse when you look round the exhibition and see the exquisite little pocket sundial. It has a built-in compass, without which it would be useless.
When I talked of the great clocks in the sky, I did not go out beyond one year, but there are potential astronomical clocks of hugely longer period. Our sun takes about two hundred million years to complete one rotation around the centre of the galaxy. As far as I am aware, no biological process has become entrained to this cosmic clock.*4
The longest timekeeper that has been seriously suggested as being influential on life is an approximately twenty-six-million-year periodicity of mass extinctions. The evidence for this involves sophisticated statistical analysis of extinction rates in the fossil record. It is controversial and by no means definitely demonstrated. There is no doubt that mass extinctions happen, and at least one of them is pretty likely to have been caused by the impact of a comet, sixty-five million years ago when the dinosaurs perished. More controversial is the idea that such events rise to a peak of likelihood every twenty-six million years.*5
Another suggested astronomical clock longer than a year is the eleven-year sunspot cycle, which might account for certain cycles in populations of Arctic mammals, such as lynxes and snowshoe hares, as detected by Charles Elton, that great Oxford ecologist, in fur-trapping records of the Hudson’s Bay Company. This theory, too, remains controversial.
Director, you invited a biologist to perform this opening, so you will not be surprised to have been regaled with stories about bees and Palolo worms and snowshoe hares. You could have asked an archeologist, and we’d all have been engrossed in tales of dendrochronology, or of radiocarbon dating. Or a paleontologist, and we’d have heard about potassium–argon dating, and about the near-impossibility, for the human mind, of grasping the sheer vastness of geological time. The geologist would have used one of those metaphors with which we struggle – and usually fail – to understand geological deep time. My own favourite one I didn’t invent, I hasten to add, although I did use it in one of my books. As follows:
Fling your arms wide to represent the whole history of evolution from the origin of life at your left fingertip to the present day at your right fingertip. All the way across your midline to well past your right shoulder, life consists of nothing but bacteria. Animal life begins to flower somewhere around your right elbow. The dinosaurs originate in the middle of your right palm, and go extinct around your last finger joint. The whole story of Homo sapiens and our predecessor Homo erectus is contained in the thickness of one nail-clipping. As for recorded history; as for Babylon, as for the Assyrian who came down like a wolf on the fold, as for the Jewish patriarchs, the legions of Rome, the Christian Fathers, the dynasties of Pharaohs, the Laws of the Medes and Persians which never change; as for Troy and the Greeks; as for Napoleon and Hitler, the Beatles and the Spice Girls, they and everyone that knew them are blown away in the dust from one light stroke of a nail-file.
If I had been a historian, I would have told stories of how different peoples have perceived time. Of how some cultures see it as cyclical, others as linear, and how this influences their whole attitude to life. Of how the Islamic calendar is based upon the lunar cycle, where ours is annual. Of how clocks used to be made, in the days before Galileo used his own heart as a clock to work out the Law of the Pendulum, and engineers perfected escapements. I would have added that the Chinese had an escapement clock, driven by water, as early as the tenth century AD.
I would have remarked how the calibration of Egyptian water clocks had to be different at different times of year, because the Egyptian hour was defined as one twelfth part of the time between dawn and dusk – so one summer hour was longer than one winter hour. Richard Gregory, from whom I learned this singular fact, remarks, mildly, that ‘this must have given the Egyptians a rather different sense of time from ours…’
If I had been a physicist or cosmologist, my reflections on time would have been perhaps most remarkable of all. I would have tried – and probably failed – to explain that the Big Bang was not only the beginning of the universe, but the beginning of time itself. To the obvious question, what happened before the Big Bang, the answer – or so physicists try in vain to persuade us – is that it is simply an illegitimate question. The word ‘before’ can no more be applied to the Big Bang than you can walk north from the North Pole.
If I had been a physicist, I would have tried to explain that, in a vehicle travelling at an appreciable fraction of the speed of light, time itself slows down – as perceived from outside the vehicle, though not within it. If you travelled through space at such prodigious speeds you could return to Earth five hundred years into the future, having yourself scarcely aged at all. This is not some therapeutic effect of high-speed travel upon the human constitution. It is an effect upon time itself. Contrary to Newtonian cosmology, time is not absolute.
Some physicists are even prepared to contemplate true time travel, going backwards in time – which I suppose must be any historian’s dream. I find it almost comical that one of the main arguments against this is the element of paradox. Suppose you killed your own great-grandmother!*6 Science-fiction writers have responded by giving their time travellers a rigid code of conduct. Every time traveller must swear an oath not to mess about with history. Somehow one feels that nature herself must erect stronger barriers than fickle human laws and conventions.
If I had been a physicist, I would also have considered the symmetry or asymmetry of time. How deep is the distinction between a process running forwards in time and one running backwards? How fundamental is the difference between a film running backwards or forwards? The laws of thermodynamics seem to provide an asymmetry. Famously, you can’t unscramble an egg; and a shattered glass does not spontaneously reassemble itself.
Does biological evolution reverse the thermodynamic arrow? No, for the law of increasing entropy applies only to closed systems, and life is an open system, driven upstream by energy from outside. But evolutionists, too, have their own version of the question whether time has an arrow of direction. Is evolution progressive?
Well, I may not be a physicist but I am an evolutionary biologist, and you had better not get me started on that fascinating question.
One of the things that any speaker can do with time is run out of it. The important business of the evening is to look at this exhibition ‘About Time’. I was privileged to be shown around it yesterday, and I can tell you it is fascinating – in all sorts of ways. It gives me very great pleasure to declare the exhibition open.
AFTERWORD
Reading this speech again, I recognize how tantalizingly brie
f my scientific vignettes on time might have seemed – not long enough to explain anything properly. My excuse is that it was my job to tantalize: and to encourage guests to proceed to the exhibition and think about time while enjoying it.
There are those who say, incidentally, that the Ashmolean should be called the Tradescantian Museum because it was originally founded to house the collections, mostly of natural history, made by the John Tradescants, father and son. The Tradescant collections were acquired (some say through dubious means) by Elias Ashmole (1617–92), who bequeathed them to Oxford University, which continued to add to them. The Tradescant natural history collections were transferred in the 1850s to the newly built University Museum of Natural History, and the Ashmolean became mostly an art museum.
There is also an argument – a different one – for changing the name of the Natural History Museum too, because so many visitors to Oxford think its name is ‘Pitt Rivers’. Though annexed to the main museum building, the Pitt Rivers Museum is an entirely separate institution with a remarkable collection of anthropological artefacts, grouped not by region, as is customary, but by function: fishing nets all together, flutes all together, timekeepers all together, and so on. To avoid the popular confusion with the Pitt Rivers, I have suggested renaming the Museum of Natural History the Huxley Museum. ‘Tradescantian’ would redress a seventeenth-century injustice but would open up a new confusion. The Huxley Museum would commemorate the alleged ‘victory’ of T. H. Huxley over Bishop Sam Wilberforce in the ‘Great Debate’ which took place in the newly built museum building. I must say I have mixed feelings about that because there is reason to think the scale of the ‘victory’ has been exaggerated.
* * *
*1 The Ashmolean Museum is Oxford’s leading museum of art and antiquities. In 2001 it staged an exhibition called ‘About Time’, featuring clocks and timekeepers through the ages. I felt honoured by being invited to open it, and this is the speech with which I did so. The text was subsequently published in the Oxford Magazine, 2001.
*2 The use of the German word for time-giver or synchronizer in the scientific literature reflects the fact that much of the classic work in the field was done in Germany.
*3 How it arose in evolution is a fascinating question. Von Frisch and his colleagues have compared the dance to various more primitive equivalents in other species of bee. Some nest out in the open and signal the direction of food by repeating a ‘take-off run’ in the horizontal plane, pointing directly towards the food source that they have discovered. Think of it as a kind of ‘follow me in this direction’ gesture, repeated several times to recruit more followers. But how did this get translated into the code used on the vertical comb, where ‘up’ (against gravity) in the vertical plane stands for ‘direction of the sun’ in the horizontal plane? There’s a clue in an odd quirk of the insect nervous system, demonstrated in insects as distantly related to each other as beetles and ants. First, a piece of background information (not the quirk): as I mentioned on this page, many insects use the sun as a compass, flying in a straight line by keeping the sun at a fixed angle. This is easily demonstrated using an electric light to simulate the sun. Now for the quirk. Experimenters watched their insect as it walked over a horizontal surface, maintaining a fixed angle to an artificial light source. They then switched off the light, simultaneously tilting the horizontal surface into the vertical. The insect continued to walk, but switched its direction so that the angle to the vertical was the same as the previous angle to the light. I call it a quirk because the circumstance is unlikely to arise in nature. It is as though there is some kind of wire-crossing in the insect nervous system, which was convenient for exploitation in the evolution of the bee dance.
*4 Indeed, I would be very surprised if one were ever found.
*5 My speech made mention of a hypothetical astronomical clock to account for it, but I have deleted it from this reprinting because modern astronomers mostly discount it and there is no direct evidence for it. Briefly, the suggestion was that the sun mutually orbits a binary companion star, called Nemesis, with a periodicity of about twenty-six million years. The gravitational effect of Nemesis was supposed to disturb the Oort cloud of planetesimals and increase the probability of one hitting Earth.
*6 You could do something far less drastic to change the course of history such that you would never be born. A sneeze would do it, given the prior improbability that any particular one out of billions of spermatozoa would succeed in fertilizing an egg.
The giant tortoise’s tale: islands within islands*1
I AM WRITING THIS on a boat in the Galápagos archipelago, whose most famous inhabitants are the eponymous giant tortoises, and whose most famous visitor is that giant of the mind, Charles Darwin. In his account of the voyage of HMS Beagle, written long before the central idea of The Origin of Species focused itself in his brain, Darwin wrote of the Galápagos islands:
Most of the organic productions are aboriginal creations, found nowhere else; there is even a difference between the inhabitants of the different islands; yet all show a marked relationship with those of [South] America, though separated from that continent by an open space of ocean, between 500 and 600 miles in width. The archipelago is a little world within itself…Considering the small size of the islands, we feel the more astonished at the number of their aboriginal beings, and at their confined range…we seem to be brought somewhat near to that great fact – that mystery of mysteries – the first appearance of new beings on this earth.
True to his pre-Darwinian education, the young Darwin was using ‘aboriginal creation’ for what we would now call endemic species – evolved on the islands and found nowhere else. Nevertheless, Darwin already had more than a faint inkling of that great truth with which, in his mighty maturity, he was to enlighten the world. Writing of the small birds now known as Darwin’s Finches, he said:
Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.
He could as well have said the same of the giant tortoises, for he was told by the Vice-Governor, Mr Lawson, that
the tortoises differed from the different islands, and that he himself could with certainty tell from which island any one was brought. I did not for some time pay sufficient attention to this statement, and I had already partially mingled together the collections from two of the islands. I never dreamed that islands, about 50 or 60 miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted.
And he said the same kind of thing about the iguanas, both marine and land, and the plants.
With the benefit of hindsight, Darwinian hindsight, we post-Darwinians can piece together what happened. In every one of these cases – and this is typical of the origin of species everywhere – it is islands that constitute the vital – though accidental – ingredient. Without the isolation provided by islands, sexual intermingling of gene pools nips species divergence in the bud. Any aspiring new species would be continually flooded by genes from the old species. Islands are natural workshops of evolution. A barrier to sexual intermingling is what you need, to allow that initial divergence of gene pools which constitutes the origin of species, Darwin’s ‘Mystery of Mysteries’.
But islands don’t have to be land surrounded by water. The tortoise’s tale has two lessons to teach us, and this is the first one. To a highland-breeding giant tortoise, each of the five volcanoes along the length of the big island of Isabela (Albemarle to Darwin, who used the traditional English names) is an island of green habitability surrounded by inhospitable lava desert. Most of the Galápagos Islands are a single volcano each, so the two kinds of islands coincide. But the big island, Isabela, is a necklace of five volcanoes, spaced from each other at approximately the same dis
tance as the single volcano on the neighbouring island of Fernandina which, from one point of view, might as well be a sixth volcano on Isabela. To a tortoise, Isabela is an archipelago within an archipelago.
Both levels of isolation have played a role in the evolution of the giant tortoises. All the Galápagos giant tortoises are related to a particular mainland species of land tortoise, Geochelone chilensis, which still survives and is smaller than any of them. At some point during the few million years that the islands have existed, one or a few of these mainland tortoises inadvertently fell in the sea and floated across. How could it have survived the long and doubtless arduous crossing without food or fresh water? Well, the early whalers took thousands of giant tortoises from the Galápagos Islands to their ships for food. To keep the meat fresh, the tortoises were not killed until needed. But they were not fed or watered while waiting to be butchered. They were simply turned on their backs so they couldn’t walk away. I tell the story not in order to horrify (although I have to say that it horrifies me), but to make a point. Tortoises can survive for weeks without food or fresh water, easily long enough to float in the Humboldt Current from South America to the Galápagos Islands. And tortoises do float.
Having reached the archipelago, the tortoises did what many animals do when they arrive on an island. They evolved to become larger: the long noticed phenomenon of island gigantism.*2 If the tortoise story had followed the finch pattern, they would have evolved a different species on each of the islands. Then, if there were subsequent accidental driftings from island to island, they would have been unable to interbreed (that’s the definition of a separate species) and would have been free to evolve a different way of life from their colleagues of different species on the new island, and also from their colleagues of the same species on other islands.*3 In the case of the finches, you could say that the different species’ incompatible mating habits and preferences now constitute a kind of genetic substitute for the geographic isolation of separate islands. Though they overlap geographically, they are isolated on separate islands of mating exclusivity. So they can diverge yet further. Most of the Galápagos Islands have the large, the medium and the small ground finch, which specialize in different diets. These three species surely originally diverged on different islands and have now come together where they coexist as different species on the same islands, never interbreeding and each specializing in a different kind of seed diet.
Science in the Soul Page 34