A guide at the Natural History Museum stated confidently that a particular dinosaur was 70,000,008 years old. When asked how he could be so precise he replied, "Well it was 70 million when I started this job, and that was eight years ago." The evident experience of Valentina Cruz, our wonderful Galápagos naturalist guide, suggests that I must add a similar margin to the estimate of 100 years that she gave us for the age of the black lava fields on the island of Santiago. The exact date of the great Santiago eruption is not recorded, but it definitely happened on one particular day in one particular year around 1900. I shall call it SV day (Santiago volcano day). I need to seem as precise as the museum guide, although the exact date doesn't matter. Perhaps it was January 19 1897, 100 plus eight years before my visit to the island.
SV day was one day in the late 19th century, a day on which, elsewhere in the world, somebody's grandfather was born at some particular hour. Somebody else died. A moustached young man in a straw boater met his true love for the first time and was never the same again. Like every day that has ever been, it was a unique day. Every second of it. It also was the date of the great Santiago volcano, the one that made the lava fields that I walked this January in the company of lava lizards, Tropidurus albemarlensis, although I knew it only when they moved and betrayed their camouflage.
Lava lizards are pretty much the only things that do move over these barren fields of black, clinker-ringing rock. And as they do so their splayed hands are feeling - though they do not know it - the fingerprints of past time. Fingerprints? Past time? Wait, that is the theme of the lava lizard's tale.
Santiago was one of the four Galápagos islands on which Charles Darwin landed in 1835, and it was the only one where he spent any time, camping for a week while Captain Fitzroy took the Beagle to fetch fresh supplies. Darwin called it James, for he and his shipmates used the English names of all the islands: the evocative Chatham, Hood, Albemarle, Indefatigable, Barrington, Charles and James. He and his small camping party had trouble finding a clear spot to pitch their tent, so thickly did the land iguanas carpet the ground. Today there are no land iguanas left on Santiago. Feral dogs, pigs and rats did for them, although there are still plenty of land iguanas on other islands of this iconic archipelago, while the closely related marine iguanas abound on all the major islands including Santiago.
The black lava fields of Santiago are an unforgettable - almost indescribable - spectacle. Black as a female marine iguana (of course the simile really should go the other way) the rock is called rope lava, and you can soon see why. It is drawn out and plaited in twisted ropes and pleats, folded and gathered like a black silk dress, coiled and whorled in giant fingerprints. Fingerprints, yes, and that brings me to the point of the lava lizard's tale. As the lizard scuttles over the black lava of Santiago it is treading the fingerprints of history, rolled out by the sequence of particular events that tran-spired, minute by minute, on one particular day late in Darwin's century, marking the minutes of that day, the day of the Santiago volcano.
There cannot be many other ways to see, laid out before you, a complete history, second by second, of one particular day, more than a century ago. Fossils do the same thing but over a much longer time scale. The molecules of a fossil are not the original molecules of the animal that died. Even fossil tracks, like those Mary Leakey found at Laetoli, don't really do it. It is true that Laetoli shows you the exact places where two individual Australopithecus afarensis (those diminutive hominids carrying chimpanzee brains around on human legs), perhaps a mated couple, placed their feet during a particular walk together. There is a sense in which these footprints are frozen history, but the rock that you see today is not as it was then. That couple walked in fresh volcanic ash which later, over thousands of years, solidified and compacted to make rock. The lava ropes and pleats of Santiago, those giants' fingerprints, are still composed of the very same molecules that were frozen into precisely those positions, only a century ago. And the time scale over which the distinct ropes and pleats were laid down is a time scale of seconds.
Tree rings do it on a time scale of years. Where the whorls of lava fingerprinting are laid down second by second, and fossils are laid down by the millions of years, each tree ring marks exactly one year. Thick rings or thin label good growth years or poor and, because every sequence of half a dozen years or so has its own characteristic pattern of good and poor years, the patterns can be recognised, again and again in different trees, as labels of particular clusters of years. Old trees and young trees show the same fingerprints so, by counting rings and daisy-chaining the patterns from increasingly ancient wooden relics, archeologists can compile a catalogue of fingerprints outspanning the longest-lived tree.
Something similar can be done with sediment patterns laid down on the sea bottom and revealed in cores of mud taken up in deep sampling tubes. And, over the longer time span of hundreds of millions of years, the named strata of the geological series are, in their own way, fingerprints of time. What is so remarkable about the lava fields of Santiago is that these fingerprints were set out on the timescale that we humans deal with every second of our lives, the time scale of musical notes, the time scale of an artist's brush, the time scale of everyday actions and the stream of human thought.
This is a real thought for a surreal landscape. And the Galápagos islands are replete with images that could have come straight from a surrealist's canvas. A tiny desert island off Santa Fe (Barrington to Darwin) looks fit for Man Friday except that instead of palm trees there are giant cactuses. As if the Arizona desert had been transplanted into an azure sea; no surrealist could have done it better. And what are sea lions doing in the Arizona desert, to say nothing of shocking pink flamingos, equatorial penguins, or flightless cor morants earnestly hanging their impotent, stubby wings out to dry? As for the large flounder that I saw when snorkelling off North Seymour Island, it was pure Salvador Dalí. Changing colour to match the corals over which it slid like an oval carpet, I would certainly not have spotted it if Valentina had not gracefully dived to point it out to me. It was only later that my wife compared the flounder to the flowing, bending watch of a Dalí painting. And wasn't that very painting, the one with the bent watches, called The Persistence of Memory ? Not a bad title for the lava fields of Santiago, scuttling ground of the Galápagos lava lizards.
Reality, if you go to the right place, and see it in the right way, can be stranger than a surrealist's imagination. No wonder Darwin drew his early inspiration from these enchanted islands.
· Richard Dawkins's latest book, The Ancestor's Tale, is a Chaucerian pilgrimage to the evolutionary past. The pilgrims are living creatures, and their tales are used to illustrate some general principles of evolution. This essay would have been included in the book if the author had written it after, instead of before his personal pilgrimage to the islands.