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Illustrations from Voyage of the Beagle (1839): top, surface view of an atoll; bottom, diagram in which Darwin proposed that coral deposits build up on the sides of sinking volcanic cones, forming a characteristic circular stucture where they meet above the summit. |
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When I visited the Priory, Adrian Green, the curator at the time, invited me to the small storehouse behind the museum, where he showed me the dramatic Griset watercolors. Spear-toting hunters chased bison or surrounded a woolly mammoth in some of the images, while other paintings depicted tribal life in the Paleolithic and Neolithic. (Lubbock had coined both terms in his 1865 book, Pre-historic Times.) Such imaginary reconstructions may seem commonplace today, but they were a bold departure from primal scenes based on stories of the Bible. It was a pleasure to view them, knowing they had been locked away for many years and had never even been published. My heart truly raced, though, when Green pulled out a triptych of a tropical coral island encircling a blue lagoon, fringed with palm trees and white sand. “This one is signed and dated 1871 by the same artist, Ernest Griset,” he said. “But we don’t have any idea what it is, or why it is archived here with Lubbock’s prehistory collection.”
I instantly had a hunch, however, strengthened when a tiny detail caught my eye—a sailing ship near the horizon of the painting’s central panel. Darwin loved coral lagoon islands and theorized about their origins. His first scientific book, which he published in 1842, was The Structure and Distribution of Coral Reefs. In it he described three types of coral reefs: barrier reefs, which rise like walls out of the sea, separated from land by a channel; fringing reefs, which stretch along a shoreline; and atolls, which are circular islands that enclose a lagoon, like the one in Griset’s painting. Could this be a long-lost representation of one of Darwin’s atolls, commissioned by Lubbock as a surprise for the 62-year-old naturalist—complete with the ship of his youth, HMS Beagle?
LONG BEFORE Darwin became interested in coral reefs and atolls, sailors and explorers had wondered how they originated. Some had suggested that fish— working together by the thousands—had built the structures by carrying grains of sand in their mouths. Others realized that the reefs had been built by billions of tiny softbodied polyps (Darwin called them “coral insects”) that secreted chambers of calcium carbonate around themselves. But why were such huge forms created, and how did atolls take on their circular shapes? Some naturalists considered coral reefs to be communal homes, like wasp nests or beehives, only on a much grander scale. No one yet had any idea of how deeply reefs were anchored in the sea, or how long it might have taken to produce one.
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Detail of the ship in Earnest Griset´s watercolor shows a striking resemblance to HMS Beagle.
Courtesy of the Bromley (Priory) Museum, Orpington, and the Lubbock Family |
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The young Darwin who embarked on the world-changing voyage of the Beagle may have been predisposed to a fascination with coral reefs thanks to his grandfather Erasmus. A physician, philosopher, botanist, inventor, and poet, Erasmus Darwin was the first naturalist in Europe to publish a coherent theory of evolution, anticipating many of Charles’s ideas by seventy years—and he did much of it in verse! (His book-length poem The Temple of Nature, for example, includes Islands and Continents raised by Earthquakes.) The Darwin family’s ancestral coat of arms consisted of three scallop shells in a row. To that escutcheon, Erasmus flamboyantly added the motto E conchis omnia (“everything from shells”). In 1770 he had it painted on his carriage, but later removed it when the local cleric’s accusations of blasphemy threatened his medical practice. It had been the eighteenth-century equivalent of displaying a Darwin Fish bumper sticker on a Kansas ambulance.
While the Beagle visited the Chilean coast in January 1835, Darwin witnessed a volcanic eruption, and he got caught in a major earthquake onshore in February. He immediately began to realize that the surrounding land exemplified the doctrine set out by geologist Charles Lyell in his Principles of Geology: that given enough time, the natural, observable forces at work today were sufficient to explain the formation of major geological features without the need to invoke supernatural catastrophes. Exploring inland, Darwin and Captain Robert Fitz- Roy found mussel beds rotting ten feet above the waterline, indicating recent uplift. That made Darwin think of marine shells he’d seen near Valparaiso, fully 1,300 feet above sea level. He concluded that “successive small uprisings, such as that which accompanied or caused the earthquake” were lifting up the land, as were oceanic volcanoes—which he observed in the Galápagos, also in 1835. In an 1844 letter, Darwin recalled that even “when seeing a thing never seen by Lyell, one yet saw it partially through his eyes.”
And so, too, Darwin was able to theorize on things he hadn’t yet seen, say coral reefs. Uplift in land areas, he reasoned, ought to be counterbalanced by oceanic subsidence. Such subsidence could explain reefs and atolls, and in turn, those structures would provide persuasive evidence that large areas of ocean floor were in fact subsiding. Darwin knew that live reef-building corals grow only in fairly shallow water, though he did not yet know why. His brilliant insight was to realize
that coral animals would keep building on top of older skeletons to stay within their zone of life as their foundation slowly sank. He wrote, “We must look at a Lagoon Island as a monument raised by myriads of tiny architects, to mark the spot where a former land lies buried in the depths of the ocean.”
From April 1 through 12, 1836, Darwin and Fitz- Roy explored the Cocos, or Keeling, Islands in the northeast Indian Ocean. That marked the first (and perhaps only) time Darwin actually set foot on a coral island [See Darwin’s diary entry left]. Investigating both
the ocean and lagoon sides of the South Keeling atoll, Darwin expressed awe that the tiny creatures could create such “monuments”:
The naturalist will feel this astonishment more deeply after having examined the soft and almost gelatinous bodies of these apparently insignificant creatures, and when he knows that the solid reef increases only on the outer edge, which day and night is lashed by the breakers of an ocean never at rest.
He was further amazed to find that delicate, branching species thrived only in the calm, clear waters of the lagoon, while much hardier, boulder-like brain corals (genus Porites) inhabited the edges, where they withstood the violent poundings of the crashing waves.
Historian of science Randal Keynes—Darwin’s great-great-grandson—wrote me that he rates Darwin’s account of his time on the Keeling Islands as one of the key passages in the whole Journal of Researches (1839), later retitled Voyage of the Beagle. “What makes the importance of the view for him particularly clear is the language of his account of it in his diary entry for 6 April 1836,” writes Keynes, highlighting Darwin’s use of the words “simplicity” and “grandeur” in his description:
[T]here is to my mind a considerable degree of grandeur in the view of the outer shores of these Lagoon Islands. There is a simplicity in the barrier-like beach, the margin of green bushes & tall Cocoa nuts, the solid flat of Coral rock, strewed with occasional great fragments, & the line of furious breakers all rounding away towards either hand.
Sandra Herbert, in Charles Darwin, Geologist (Cornell University Press, 2005), also calls attention to the fact that he used those “two of his favorite words” to describe atolls, words found in the famous last sentence of On the Origin of Species:
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
Ernest Griset’s 1871 triptych of an atoll. The long-forgotten watercolor was discoverd by the author in the a British museum storeroom among a cache of paintings commissioned by John Lubbock. It may have been timed to celebrate Darwin’s revised and updated 1874 reissue of the 1842 treatise on coral reefs.
Courtesy of the Bromley (Priory) Museum, Orpington, and the Lubbock Family
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Darwin’s delight in and admiration of the Keeling atolls spurred him to complete his theory of coral reef formation, which he had conceived in the earthquakes of Chile and developed further after seeing the spectacular, reef-ringed volcanic island of Moorea (then called Eimeo), near Tahiti, in November 1835. (Now part of French Polynesia, mysterious-looking Moorea was the model for the island of Bali Ha’i in the Rodgers and Hammerstein musical South Pacific—though not in James Michener’s novel Tales of the South Pacific, on which the musical was based.) Although the Beagle did not land on Moorea, Darwin got a very good view of it by climbing more than two thousand feet up a Tahitian mountain. The island’s skyline of jagged volcanic peaks rose abruptly from the mirror-still lagoon sheltered by its barrier reef. Darwin was struck by the evidence that vast areas of the ocean f loor—not just larger landmasses—were seething with activity, both seismic and animal. In Voyage of the Beagle he wrote:
We feel surprise when travelers tell us of the vast dimensions of the Pyramids and other great ruins, but how utterly insignificant are the greatest of these, when compared to these mountains of stone accumulated by the agency of various minute and tender animals! This is a wonder which does not at first strike the eye of the body, but, after reflection, the eye of reason.
UPON HIS RETURN to England in the fall of 1836, Darwin couldn’t wait to explain his theory of coral reefs to Lyell. Less than a month after the Beagle docked, the two men met for the first time.
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John Lubbock, Darwin’s only student, examines a captive colony of ants in 1900.
Courtesy of the Lubbock Family |
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As Darwin related it to a friend, Lyell “was so overcome with delight that he danced about.” Lyell soon wrote to Darwin, “I could think of nothing for days after your lesson on coral reefs, but of the tops of submerged continents. It is all true, but do not f latter yourself that you will be believed, till you are growing bald, like me, with hard work & vexation at the incredulity in the world.”
Lyell reveled in Darwin’s theory even though it differed from his. As coral expert and historian of science David R. Stoddart at the University of California, Berkeley, explains, to account for the circular form of atolls, “Lyell had suggested that the corals colonized the rims of slightly submerged volcanic craters. Darwin on the other hand proposed a sequential transformation of fringing reefs into barrier reefs and then into atolls as the corals continued to grow upwards through repeated slight movements of subsidence of the usually volcanic reef foundations.”
Throughout the nineteenth century—and after Darwin’s death in 1882—Darwin’s theory of reef formation remained contentious. Alexander Agassiz, son of the anti-evolutionist Harvard zoologist Louis Agassiz, spent forty years and his considerable fortune visiting hundreds of the world’s reefs, but died before he could write a contradictory theory. For some decades, around the turn of the century, Darwin’s coral reef theory, like his evolution theory, fell out of favor with scientists, but eventually both returned with renewed vigor. The saga of the controversies that surged around the coral theory has been beautifully told in Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral (Pantheon, 2005) by David Dobbs.
Agassiz and others thought they had found reefs forming in areas where the seafloor was lifting rather than sinking. Some geologists even blasted Darwin’s method of doing science: rather than seeking patterns of coral reef distribution on charts and maps, they argued, he needed to visit more reefs firsthand, as they had done. However, Darwin thought that more visits to reefs were pointless unless “some doubly rich millionaire” could be induced to make deep core drillings that would reveal their structure.
Not until 1950—while attempting to destroy Eniwetok, an atoll in the Marshall Islands, near the equator in the Pacific Ocean—did science find definitive answers. Preparatory to testing a hydrogen bomb there, the U.S. Government sent geophysicists to drill test cores of the coral deeper than anyone had previously done. Dobbs relates that finally, at 4,200 feet, the drills hit “a greenish basalt, the volcanic mountain on which the reef had originated.”
Dating of the tiny fossils in the bottommost layer of coral showed that the reef had gotten its start in the Eocene. For more than thirty million years this reef had been growing—an inch every millennium—on a sinking volcano, thickening as the lava beneath it subsided.
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A Brief History of Reef Science
By Jennifer A. lane
Coral reefs are among the most intricate and diverse ecosystems on Earth, yet people long considered them mainly as sources of food and dangers to navigation. Scientific understanding of corals dates back less than 300 years, to 1727. That's when the French naturalist Jean André Peyssonnel identified corals as animals. Scholars, who at the time presumed they were plants, or perhaps rocks, laughed Peyssonnel out of the French Academy of Sciences. Subsequent research proved Peyssonnel correct, launching an effort to catalog the world's coral species.
Among the first to be described scientifically were specimens collected in the South Pacific during the first voyage of Captain James Cook, between 1768 and 1771. The next major advance in understanding came in 1842, when Charles Darwin explained coralreef formation. Post-Darwinian discoveries have involved nearly every area of science, from geology and zoology to human medicine. Taxonomic studies have identified some 850 extant reef-building coral species, as well as tens of thousands of reef-dwelling organisms, and ecological research has illuminated the complex interrelationships among them.
An important landmark in reef biology was the 1931 finding by the British scientist Charles M. Yonge that single-celled photosynthetic algae called zooxanthellae, which inhabit the digestive cells of reef-building corals, are symbionts. The oxygen and nutrients they produce speed their hosts' growth, letting the uppermost portion of the reef remain near the life-giving light and warmth of the ocean surface, even as the seafloor subsides. The energy captured photosynthetically also helps make reefs unusually productive and diverse, comparable to tropical rainforests.
Examination of fossil reefs has revealed their long evolutionary history. In 1924, the paleontologist Percy E. Raymond described the Chazy Reef formation of Isle La Motte, Vermont, as “the oldest coral reef in the world.” At approximately 450 million years old, Chazy is the earliest known reef in which primitive corals began to play a small structural role. The first modern stony corals appeared more than 200 million years later.
We now know that reefs existed long before the first corals evolved. Microscopic algae built the earliest reefs—leathery algal mats interleaved with sediment, called stromatolites—at least 2 billion years ago, before multicellular lifeforms had evolved, and possibly much earlier. Later, the spongelike archaeocyathids, now extinct, became the first animals to build reefs. Bryozoans, tiny colonial animals that secrete a hard calcareous skeleton much like that of modern corals, briefly dominated reef building until they were replaced by primitive corals, according to Roger J. Cuffey, a geologist at Pennsylvania State University in University Park.
Many reef studies have had even broader scientific implications. In 1963, the late Cornell University geologist John W. Wells used the finding that corals grow faster during the day than at night to show that Earth's rotation has been slowing, because of friction induced by the tides, by about two seconds per 100,000 years. From the rhythm of daily growth evident in fossil coral, Wells calculated that during the Devonian period (between 417 million and 354 million years ago), a year had approximately 400 twenty-one-hour days.
In recent decades, reef ecosystems have become the source of important new treatments for various human maladies: the chemotherapy drug Ara-C and the anti-viral drugs AZT and Acyclovir derive from compounds isolated from a Caribbean sponge, for example. Scientists continue exploring the biology of coral reefs, focusing not only on benefits to people, but on preserving reefs from the substantial threats they face.
Jennifer A. Lane is a doctoral student in evolutionary biology at the City University of New York and the American Museum of Natural History, both in New York City.
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Over the next few years, many more drillings and echo soundings confirmed that with rare exceptions, reefs had formed only in areas of sea floor subsidence all over the Pacific and Caribbean. Although Darwin couldn’t have foreseen it, his model fit perfectly with theories of plate tectonics. In David Dobbs’s words, “the movement of the earth’s huge plates explains the subsidence of the Pacific and many other reef areas. Darwin’s theory was astoundingly correct.”
And it was as correct biologically as it was geologically. We know now that reef-building corals thrive only where their symbiotic, photosynthetic algae can receive sufficient sunlight to generate nutrients for the polyps (a depth of about eighty feet seems to be optimal). While the ocean floor beneath them keeps sinking, colonies keep reaching upwards to receive sunlight. As they do so, they secrete calcium carbonate, adding their minute contribution on top of the accumulated skeletons of millions of years. [See sidebar on opposite page for more information on corals.]
TRUTH TO TELL, not all of this raced through my mind as I beheld Ernest Griset’s painting of an atoll. But I was well acquainted with Darwin’s theory of coral reefs, and perhaps more important, I knew about his close association with John Lubbock, who commissioned the artwork. Lubbock’s father (also named John) was the major landowner in the Kent countryside. The family’s huge estate, High Elms, with its twenty-two room mansion, was about a mile and a half from Down House, Darwin’s home. Indeed, Darwin’s property was a small island in the holdings of Lubbock.
From the age of eight, the younger John was mentored by Darwin, twenty-five years his senior. As he matured, Lubbock took up many of his teacher’s interests, including classification of barnacles, the relationship between insects and f lowers, paleontology, and human prehistory. Later an inveterate collector of prehistoric stone tools, ethnographic artifacts, and insect colonies, young Lubbock must have filled his indulgent father’s mansion with birds’ nests, fossils, and flasks of pond water. So fascinated was the son by tales of the South Seas that he built an artificial grotto decorated with corals and shells near the big house.
Darwin frequently walked the footpath between his home and High Elms, where he may have offered advice during the planning of Griset’s paintings or viewed and discussed each one as it was completed. However, neither Darwin nor Lubbock ever used them to illustrate their books. And by the mid-twentieth century, the paintings had been removed by the family from High Elms. That was fortunate, because in August 1967 the great mansion burned down (oddly, on what the grateful British populace had dubbed “St. Lubbock’s Day,” the secular bank holiday Lubbock instituted). The estate grounds are now a public park and nature reserve.
When Lubbock commissioned the triptych of the coral atoll, Darwin was preparing to reissue a revised and updated edition of The Structure and Distribution of Coral Reefs, three decades after its initial publication. It seems plausible that Lubbock planned the painting as a surprise for Darwin, to commemorate that significant milestone. In Griset’s brushstrokes, Darwin’s tropical atoll appears isolated beneath a vast sky— jewel-like, pristine, and mysterious. The sailing ship is barely sketched in, but it is unmistakably a classic brig-sloop of the Cherokee class [see painting detail above]. It even has a stripe along the hull and gun ports along the side, as the Beagle did.
The painting remains sequestered against English winters in the stone-brick storeroom at the Priory. Within its timeless world, the atoll awaits the arrival of the iconic sailing ship on the horizon, bearing a young man who seeks to elucidate its mysteries. While studying corals, he will experience serendipity on a grand scale. By casting his “eye of reason” on natural phenomena that, operating over immense periods of time, create “forms most beautiful and most wonderful,” he will change forever our view of life.
Web links related to this article:
Hear author Richard Milner interviewed by Vittorio Maestro,
Editor in Chief of Natural History. (MP3, 22 minutes, 35 seconds)
Contributing Editor Richard Milner, an associate in the Division of Anthropology at the American Museum of Natural History, has performed his one-man musical, Charles Darwin: Live & In Concert, worldwide. His new book, Darwin’s Universe: Evolution from A to Z, will be published this spring by the University of California Press.
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Copyright © Natural History Magazine, Inc., 2009
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