by Tim Flannery
Some of the Messel birds—including falcons, hoopoes, an owl, ibises and an ancestral pheasant-like creature—are to be expected. But others are out of place, unexpected or downright bizarre. Among those out of place are a kind of potoo (a nocturnal bird like a nightjar), a hummingbird, a sunbittern and a relative of the carnivorous cariamas, all of which today inhabit South America, but not Europe. A primitive ostrich-like creature and a mouse bird (today, exclusively African) also join this group. Among the unexpected is a kind of gannet that hunted over freshwater, while among the bizarre must surely be counted a parrot that lacked a parrot-like bill, and a strange creature that looked like a mixture between a hawk and an owl, but which had membranous, ribbon-like breast feathers.7 What is missing from Messel and indeed all of Europe at this time are ancestral larks, thrushes, orioles and crows, all perching birds, despite the fact that the greatest part of Europe’s avifauna today consists of perching birds.
What to make of the high proportion of South American bird species at Messel? Oddly, there is good geological evidence that at the time South America, though it lay close to Africa, was entirely isolated by water, so over-water migration was the only possible route. As things stand, we have no convincing explanation as to why so many birds that are restricted today to South America flourished in Eocene Europe.8
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* The first name in celebration of the bicentenary of the birth of Charles Darwin, the second from the Roman name for Messel.
* It is not known how much was paid for the cleverly tricked-up specimen, but I suspect it was a great deal.
CHAPTER 11
The European Great Coral Reef
It’s 1 June 2016 and I’m standing in front of a grey cabinet that holds the Natural History Museum’s collection of fossil corals, hardly believing what I’m seeing. It looks like an irregular lump of rock, but Brian Rosen, one of the museum’s coral researchers, explains that it is in fact the holotype (the name bearer for the species) of Acropora britannica—a member of the great Acropora, or staghorn group of corals, which today are among the most important of the reef-building corals. Named by Dr Carden Wallace, an Australian expert on this group of reef-forming corals (the Acroporidae), it was found in 37-million-year-old (latest Eocene) sediments near the picturesque village of Brockenhurst in the New Forest, near Southampton.
The rocks around Brockenhurst have yielded fragments of an extraordinary marine fauna, including Acropora anglica and britannica—two species that are among the earliest members of the two great branching coral species groups—‘robusta’ and ‘humilis II’—which make up most of the ocean-front corals in the Indo-Pacific today.1 Could Brockenhurst in the New Forest really have been the birthplace of Earth’s magnificent coral reefs? For more than a century, geologists have known that 37 million years ago the Brockenhurst area was where the coast of the proto-European continent faced the open Atlantic Ocean. There, according to one nineteenth-century geologist, ‘coral reefs exposed to furious surf and the wash of a great ocean’ had formed a bulwark against the southerly wind and swells.2
Recent researchers doubt that an actual coral reef occurred in the Brockenhurst area, though reef-forming corals clearly grew there, and fast-growing branching corals such as Acropora thrive in such energetic environments. Moreover, Brockenhurst does not mark the beginning of the Acropora genus, for there are a few older fossils from France, and a single record from Somalia, dating to around 55 million years ago. The Brockenhurst fossils, however, do form part of the evidence that many modern coral reef organisms originated in the European section of the Tethys Sea.
Thanks to a most exceptional fossil deposit in Italy, we know a little about the animal communities that thrived when the Acropora corals first evolved. For more than 400 years, travellers have been visiting Monte Bolca near Verona to peer into a 50-million-year-old fishbowl, or Cava della Pesciara, as the Italians call it. The very earliest written record of a visit to the site, by Pietro Andrea Mattioli, dates to 1554: ‘some slabs of stone which, on being split in half, revealed the shapes of various species of fish, every detail of which had been transformed into stone’.3 Over the years noblemen, cardinals and even the emperor Franz Joseph passed through, and left with fossil fish mementos.
About 50 million years ago, when the fossils were living creatures, the rocks of Monte Bolca were forming in the Tethys Sea. The fish and other creatures preserved in the deposit appear to have inhabited a lagoon that formed between the land and a reef (though modern reef-building corals such as Acropora have not been found there). Nearby, the remains of crocodiles, turtles, insects and plants have been found, all exquisitely preserved. Among the plants are coconuts and other palms, figs and eucalypts.4 The fish fossils are some of the most spectacular and beautiful found anywhere on Earth: some look as if they are still swimming and retain traces of patterning and colour.5
The marvellous preservation of the fossil fish from the Pesciara cannot be fully explained. The best theory to date is that occasionally a toxic algal bloom broke out that killed the fish en masse and their bodies drifted down to oxygenless water in the lagoon’s deeper parts. Whatever the cause, about 250 species of fish are represented in the deposit. And we would have none of them except for an unlikely geological event. The entire region around Verona was volcanic and highly unstable at the time the layers formed. Before it had hardened to rock, the slab of sediment containing the fish, which is several hundred metres long and 19 metres thick, was transported, intact, a considerable distance—perhaps by an underwater landslide.
The most important thing about the Monte Bolca fauna is that it is the oldest known occurrence of the community of fish that inhabit coral reefs today. Despite the presence of a few now-extinct fish families, the 250 species preserved at the site are broadly similar in type and form to kinds that can still be seen on the world’s reefs, including rays, angelfish and eels. But both butterfly fish and parrotfish, which abound on modern coral reefs, are absent from the deposit, suggesting that they probably evolved later.6 An astonishing exception, however, is a single fossil of a handfish, so-named because they ‘walk’ on fin-like hands. Today they occur only in the cold waters of southern Australia.* Some years ago I had a choice of visiting the Galleria dell’Accademia in Florence to see Michelangelo’s David, or going to the natural history museum in Verona to see the fossil fish. You can guess which I chose. I arrived in Verona on a sunny Thursday and made a beeline for the museum, which is located across the river from the city centre, and was dismayed to discover that it was closed without notice. In a tale that I’m sure is familiar to many museum goers in Italy, I returned the following day only to find that the museum was closed from Friday to Tuesday each week, the very day I was booked to leave the city! My only consolation was roaming Verona’s well preserved Roman arena, where some of the tiered seats contain the remains of ammonites the size of truck tyres, their surfaces polished to a gem-like finish by the posteriors of ancient Romans. Did they, I wonder, ever ask themselves what those great round shell-like shapes were doing there in their rocky seats?
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* The Monte Bolca handfish is known as Histionotophorus bassani. Of the 14 living species, 11 are restricted to Tasmania. In the Eocene, they must have existed along the length of the Tethys.
CHAPTER 12
Tales from the Sewers of Paris
Around the time the Monte Bolcan fish were breathing their last, a region in northern France was a languorously warm embayment of the Atlantic Ocean. The sediments that fell to the bottom of that sea are now known as the rocks of the Paris Basin, and in 1883 the French geologist Albert de Lapparent—who is perhaps best known for his efforts to link Britain with the rest of Europe by a rail tunnel—coined the name Lutetian (after the Roman name for Paris) for the geological age during which the rocks of the basin were formed.
The Paris Basin rocks include the famous Paris stone—a limestone that has been used for construction since Ro
man times—and whose warm creamy-grey colours give the city an unmistakeable beauty. As I wander its streets, it’s not just scenes of the French Revolution that fill my mind, or the delicious smells of fresh bread and cheeses that beguile me, but traces of that long-ago Paris—a place of marine giants and tropical creatures—and a wondrous biodiversity.
There is no better place to see the traces of Paris’s lost glory than at the Muséum Nationale d’Histoire Naturelle in the Jardin des Plantes. One of the world’s oldest museums, it’s where both le Comte de Buffon and Georges Cuvier (the father of palaeontology) spent their working lives. During the opening decades of the nineteenth century, Cuvier laid down a number of ‘doctrines’, some of which survived the test of time better than others. He was right in arguing that extinction did occur (a fact doubted in his day), but wrong in arguing against evolution.* Instead, he developed the idea that catastrophes had periodically extirpated life, and each time God had created life anew. This was a logical consequence of his reading of the fossil record.** As Cuvier saw it, most fossil species remain similar in form from their first occurrence to their last, and ‘missing links’ are extremely rare. This was also known to Darwin, and it worried him exceedingly. But Darwin perceived what Cuvier did not: that prehistory is so vast that fossils give us nothing but the tiniest glimpse into the life of times past. As Signor-Lipps point out, this means we almost never see the origin of a species or its final extinction in the fossil record.
Some of Cuvier’s most enduring work was undertaken with Alexandre Brogniart, a teacher at the Paris Mining School. Together they examined fossils that had been unearthed around the city, many of which were encountered during the excavation of Paris’ famous sewers. Another prolific area for discovery was Montmartre, where mining for gypsum to make plaster of Paris almost undermined the famous hill.*** It was the abundance of fossils, from both terrestrial and marine environments, preserved there that allowed Cuvier to work out the rules of geological succession (that younger rocks overlie older ones).
Despite a long-term global cooling trend, conditions in the shallow seas around what was to become Paris remained favourable for the growth of marine organisms.1 One beneficiary was the giant bell-clapper shell (Campanile giganteum) described in 1804 by Jean-Baptiste Lamarck.* Perhaps exceeding a metre in length, it was the largest gastropod ever to exist, and its remains, which are largely restricted to the Paris Basin, were frequently encountered during the excavation of the sewers. A single species of bell-clapper shell survives today—in rocky habitats in the cool, shallow, waters off southwest Western Australia. While reaching only a quarter the length of its gigantic European relative, it is a rare and wondrous reminder of the glories that once swarmed the sea where Paris stands today.
But what of life elsewhere in the Tethys, that marvellous lost sea that bathed the proto-continent in salty, balmy warmth? Another true giant was the largest cowrie that ever lived, Gisortia gigantea. Its exquisitely fossilised shells, the size of rugby balls, date back 49–34 million years. They have been found in places as widespread as Bulgaria, Egypt and Romania. Cowries, with their porcelain-like lustre, are among the most beautiful of all gastropods. Sadly, nothing even remotely similar in size to the great Gisortia survives in today’s oceans.
The Tethys was also the headquarters of the mighty Nummulites, a few species of which survive in the Pacific today. The name is derived from a Latin word meaning little coin, and these single-celled organisms abounded during the Eocene. Nummulites creep along the bottom of the sea, feeding on detritus, and laying down disc-like, many-chambered internal shells of calcium. The Tethys provided a perfect habitat for them: tropical, shallow and sunlit. In Turkey, fossil Nummulites as large as 16 centimetres in diameter have been found. These giants are estimated to have lived for a century, making them the longest-lived single-celled organisms known.2
Such was the abundance of Nummulites throughout the length of the Tethys that in many places their remains formed a distinctive kind of rock called nummulitic limestone which, since ancient times, has been much favoured for construction. The origin of this ubiquitous rock—it was used by the ancient Egyptians for construction of the pyramids—was long a source of mystery. Herodotus spread one early misconception: that the Nummulites were the petrified remains of lentils which the Egyptians fed to their slaves as they laboured over the mighty structures. But even in the early twentieth century, the presence of Nummulites in the pyramids continued to befuddle, as the sad tale of Randolph Kirkpatrick, assistant keeper of lower invertebrates at what is now the Natural History Museum, London, illustrates.
One of the greatest battles in geological science was that waged between the Plutonists and Neptunists on the origins of Earth’s surface. The Plutonists, who had Thomas Huxley on their side, asserted that rocks such as basalt and granite, which originated in a molten state deep within the Earth, were the primary source, and that the other rock types such as sandstone and slate were formed from their breakdown and re-deposition as silt and mud. The opposing Neptunists, who counted Goethe among their number, believed that the Earth was originally covered in ocean, and that all rocks originated as deposits on the floors of ancient seas. By the mid-nineteenth century the matter had been all but settled in favour of the Plutonists. But then in 1912, Kirkpatrick, dropped a bombshell that reignited the debate.
It had not escaped Kirkpatrick’s notice that the pyramids were almost entirely composed of Nummulites. As he scoured rocks for evidence of yet more Nummulites, he began seeing them in every rock type he placed under his microscope. In his great opus, The Nummulosphere (which opens with a stupendous frontispiece featuring Neptune driving a quadriga over a watery globe), Kirkpatrick used this supposed ubiquity of Nummulites to revive the theory of the Neptunists, arguing that the entire crust of the planet, and ultimately the Solar System and the Universe, consisted of the fossilised fragments of Nummulites that had lived in a primal sea.3
Historians of science have often wondered how a staid and doubtless sober curator at one of the world’s most august natural history institutions could go from publishing serious and important research to making such outrageous claims. When I have discussed the question with experts on corals, they tell me that a life spent researching the complex biology of organisms like corals and sponges can alter a man. George Matthai worked at the Natural History Museum shortly after Kirkpatrick. After describing countless new species of corals, including many of those that make up Australia’s Great Barrier Reef, he suicided.
Matthai’s colleague Cyril Crossland also suffered for the cause. In 1938, after decades of strenuous work studying corals in British, Egyptian and other research institutions, he took up a position at the University of Denmark’s Zoological Museum. Perhaps extreme dedication to his research saw him eschew the dangers emerging to the south, or perhaps his deafness left him unaware. Prior to his death in 1943 he was seen riding Copenhagen’s trams, roundly abusing the Nazis in a cultivated English accent. The heroic if rash Crossland was sadly missed by his colleagues, who named sixty species of marine organisms after him.
Apart from his obsession with Nummulites, Kirkpatrick exhibited no signs of mental infirmity. He was sincere in his beliefs about the Nummulosphere and he published images that he claimed depicted the remains of Nummulites in basalts, granites and meteorites—rocks in which no fossils have ever been found—so that others could verify his claims. My son David, who is also a scientist, on hearing Kirkpatrick’s story, remarked to me that many a researcher, after spending thousands of hours peering down a microscope at some repeated shape, begins to see it repeated ad nauseam on blank walls, distant vistas, even a spouse’s face. And it’s not just images but theories that can get imprinted and reflected, causing a scientist to see evidence for their favourite theory everywhere. Perhaps the affliction should be known as nummulitis.
As Kirkpatrick worked, Otto Hahn—an intensely patriotic German lawyer and amateur petrologist turned Swedenborgian who believed life o
riginated in outer space—was spending long hours staring down his microscope at what he took to be the fossilised remnants of algae. Hahn, like Kirkpatrick, was a Neptunist, but he thought the idea that the Earth’s rocks were made of Nummulites was ridiculous. He proposed that they were composed of a fossilised forest of algae which had originated on meteorites. He also ‘discovered’ the fossil of a minute, triple-jawed, algae-eating worm, which he named Titanus bismarcki, in honour of the German chancellor. Bismarck had other things on his mind, for the European powers had embarked on the Great War.
By 49 million years ago, the continued growth of the proto-continent of Europe was profoundly altering the seaways surrounding it. To the south, the Tethys was narrowing, as was the Turgai Strait, separating Europe from Asia. Except for a recently formed and still narrow north Atlantic, the ever-narrowing Turgai was the only connection between the waters of the Arctic Sea and the rest of the world’s oceans.
The Arctic Sea has not always been frigid and ice-covered. Forty-nine million years ago it was more like the Black Sea of today—with its oxygenless and very deep salty layer beneath fresher waters—though the Arctic Sea was then more tropical than today’s Black Sea. This was also a time of intense rainfall, and as the Arctic Sea became more cut off from the rest of the ocean, the runoff from rivers began to pool in its upper layers, which freshened to the point that a particular kind of weed, known as Azolla, could grow there.