Europe
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The Messinian salinity crisis changed the world. The global sea level rose by 10 metres because the water evaporated from the Mediterranean was added to the seas elsewhere, and during the century it took for the Mediterranean to refill, the oceans fell by 10 metres. So much salt—about a million cubic kilometres—was locked up in the sedimentary layers underlying the Mediterranean that the salinity of all of Earth’s oceans remains reduced. Because freshwater freezes at higher temperatures than salt water, the surface layers of the oceans near the poles froze more readily. As the climate continued to cool, this would hasten the onset of the ice ages.
The end of the Miocene is dated to 5.3 million years ago. Although it roughly coincides with the end of the Messinian salinity crisis, the Miocene’s end is not defined by this event. Indeed, it is not marked by any global cataclysm, but rather by the extinction of an obscure and tiny plankton known as Triquetrorhabdulus rugosus. Geologists often choose the extinction of a species of plankton to define the end of a geological period, because the tiny fossils are widespread and easily found, making it possible for palaeontologists to trace the event globally.
This is sound science, but the poet in me chafes against it. Surely the beginning of a new geological epoch is portentous and should be marked by more than the passing of a microscopic algae? One such possibility for the dawn of the Pliocene is the origination of the genus Gadus, which is significant because it includes that most economically important fish, the cod.1 Europeans have enjoyed ‘fish and chips’, bacalao and other cod-based delicacies for centuries, so surely a case can be made for this fish to be the herald of the Pliocene. Yet I sense I’m fighting a losing battle—to take a small liberty with Philippians 4:7: the ways of geologists can, like a piece of cod, passeth all understanding.
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* The Messinian age is named for layers of evaporite rocks that outcrop near Messina, Sicily.
* It is difficult to be more precise about the highest points of the Mediterranean Islands six million years ago.
CHAPTER 21
The Pliocene—Time of Laocoon
If we cannot define the advent of the Pliocene by the rise of cod, then perhaps we should abolish it altogether. It is after all ridiculously brief and has nothing much to distinguish it from the Miocene. As currently defined, it extends from just 5.3 million to 2.6 million years ago. Named by Charles Lyell, a rough translation is ‘continuation of the recent’. The great man appears to have slipped up when minting the name—so egregiously indeed that the lexicographer Henry Watson Fowler, of A Dictionary of Modern English Usage fame, lambasted the name of the epoch as a ‘regrettable barbarism’.* Lyell justified it on the rather lame basis that many Pliocene molluscs are similar to living species. But what is really characteristic of the Pliocene, in Europe at least, is that it was a time of giants. In effect, the Pliocene is Europe’s last, great flowering, after which the continent’s biodiversity entered a decline.
A map of Pliocene Europe has that uncanny quality of being familiar, yet not quite right. Looking to Iceland’s east we see that the entirety of Scandinavia is not so much missing as combined into a massy lump of land that forms a northwestern bulwark of Europe. This is because the basin of the Baltic Sea is yet to be carved from the rock. And where is Britain? Like Scandinavia, it is embedded in a broad peninsula, this one projecting northwards from present-day France. Neither the English Channel nor the Irish Sea exist. To the south, the form of the Mediterranean lands is even more disconcerting. Beginning in the west, the Baetic Cordillera (comprising the Sierra Nevada and the Balearic Islands) is still a single, mountainous island located at the entry to the Mediterranean, where the Strait of Gibraltar is today. Tuscania lies to its east, attached to the mainland by a peduncle as if hanging from the Maritime Alps. Italy, meanwhile, is broadly connected to Turkey, mainland Greece is a lesser peninsula, while parts of eastern Europe as far north as Romania are under the waves.
How to account for these many differences? Sea levels were 25 metres higher in the early Pliocene than they are today. Yet many parts of Europe that are under the sea now were dry land then. This is because, in the north, the erosion caused by subsequent glaciers and frozen sheets of the ice age have chiselled away at the land, carving channels and gulfs that give northern Europe its current topography. But much of the work in shaping contemporary Europe’s south was done by the restless energy of the tectonic plates, driven by a northward-moving Africa.
Average global temperatures during the Pliocene were 2–3° Celsius warmer than they are today, and until three million years ago the northern ice cap formed on the Arctic Sea only during the winter. But the climate was cooling, and Europe was becoming drier and more seasonal, favouring the spread of deciduous and coniferous forests across the north. Prior to the ice ages—right up to the end of the Pliocene—Europe’s forests were broadly similar to those of North America and Asia today. They were made up of a great number of species, including wing-nut (a relative of the walnut), hickory, tulip-tree, hemlock, blackgum, sequoia, swamp cypress, magnolia and liquidambar, which are no longer found in Europe, along with familiar European types such as oak, hornbeam, beech, pine, spruce and fir.*
Botanists refer to this vegetation type as the Arcto-Tertiary Geoflora. Its loss from Europe at the end of the Pliocene is called the Asa Gray disjunction, after the great nineteenth century American botanist who so convincingly explained its causes. At the time Gray worked, the ice ages were a mystery, though it was clear that in the distant past the earth had been far colder than it is today. Gray argued that the most cold-sensitive trees of the Arcto-Tertiary Geoflora had been squeezed against the alps by the growing chill, until they were exterminated. Asia and North America, in contrast, have uninterrupted, forested coastlines that run from equator almost to the pole, providing a migration corridor for species as the climate changed.1
Asa Gray’s concept reverberates through moral, philosophical and cultural dimensions of European landscapes. Without his work we would see the glorious golden autumn foliage of a liquidambar, or a spring magnolia in full bloom, as alien to Europe. But such trees are mere prodigals, albeit prodigals forced two million years ago from their native homes, and now returning, courtesy of colonial-era botanists and a warming climate.
Incidentally, over the millennia, Asia has provided a refuge for far more of Europe’s biological heritage than just the Arcto-Tertiary Geoflora. Many organisms that became extinct over Europe’s long history have survived in the rainforests of Malaysia and in regions to its north and east. For example, close relatives of the nipa palm and water cypress that grew in Germany 47 million years ago continue to thrive in Malaysia. The cannonball mangrove that thrived in Bavaria 18 million years ago can still be seen in the Indo-Malayan archipelago. And remember the saratoga fish from Hainin, and the pig-nosed turtles from Messel? Europeans can effectively time-travel to the distant past of their continent by boarding a jet bound for the Malay Archipelago.
Some of the most intriguing creatures ever to inhabit Europe lived during the Pliocene, and the most fascinating of all have, tragically, been lost forever. The remains of one remarkable animal were recovered during what is arguably the last of Europe’s religiously inspired wars—the Crimean campaign of 1853–56. During the conflict, as the naval and land assaults on Sevastapol dragged bitterly on and the Light Brigade carried out its fatal charge, Captain Thomas Abel Brimage Spratt, commander of HMV Spitfire, rendered distinguished military service, in recognition of which he was made a Most Honorable Military Member of the Order of the Bath. Spratt was a man after my own heart. Somehow, amidst the shell and rifle fire, he found time to look for fossils, and as he rummaged the rocks near Thessaloniki, he discovered something quite special. He returned to Britain with his collection, and in 1857 the great anatomist Sir Richard Owen set to work identifying the specimens Spratt had passed on to him.
Owen began his career at the Royal College of Surgeons. He was a horrible man; his biograp
her Deborah Cadbury saying of her subject that he ‘had a penchant for sadism’ and was ‘driven by arrogance and jealousy’.2 He was perhaps at his worst when dealing with his great rival in describing dinosaurs, Gideon Mantell. Mantell, who had discovered the dinosaur Iguanodon, a feat that Owen so envied that he claimed to have discovered the creature himself. As the rivalry between the pair escalated, Mantell said of Owen that it was ‘a pity that a man so talented should be so dastardly and envious’. Over the years Mantell named four of the five dinosaur genera then known, which only acted to fuel Owen’s envy.
Mantell was a medical doctor, but he was so absorbed in his palaeontological research that his practice suffered. He moved to Brighton on England’s south coast in the hope of better fortunes, but he was soon destitute and was forced to sell his fossil collection to the British Museum, where Owen was already influential.* Mantell asked for £5000 but settled for £4000—a poor price indeed for an arrangement that placed the fruits of his lifetime of palaeontological labour at his rival’s disposal. But poor Mantel’s degradation did not end there. In 1841 he suffered a carriage accident in which he fell from his seat and became entangled in the horses’ reins. As he was dragged across the ground, his spine was gravely injured. To deal with the ongoing pain he took opium, but in 1852 it all became too much, and the good doctor overdosed. After his death, in a reptilian act, Owen had someone remove the damaged section of Mantell’s spine, which he pickled and stored in a jar, and it joined Mantell’s dinosaurs as one of Owen’s trophies.
Owen rejected out of hand Darwin’s theory of evolution, perhaps in part because he was as cunning a politician as he was a brilliant anatomist. Yet somehow his scientific reputation survived even his dogged adherence to Creationism. In fact, the terrible truth is that Sir Richard Owen, KCB, FRMS, FRS, president of the British Association for the Advancement of Science and darling of the nobility, got away with almost everything. For 90 years—until 2008—his statue held pride of place at the top of the grand staircase in the British Museum of Natural History. And Mantel’s spine languished in its glass jar at the Royal College of Surgeons until 1969, when it was destroyed to free up space.
Owen fancied that he knew the internal structure of every creature on earth, but the fossils Spratt had collected near Thessaloniki forced him to expand his studies. Spratt’s thirteen bones, Owen concluded, could belong to no other snake than a viper. What was confounding, however, was its size, for the bones must have come from a creature at least three metres long. To explain this, Owen resorted to the classics:
The classical myth embalmed in the verse of Virgil and embodied in the marble of the Laocoon, would indicate a familiarity in the minds of the ancient colonists of Greece with the idea at least of serpents as large…But according to actual knowledge, and any positive records of zoology, the serpent…must be deemed an extinct species.3
Owen named the remains of what was clearly a very large and formidable viper Laophis crotaloides—the ‘rattlesnake-like snake of the people’.4
It strains credulity that such an important fossil as Laophis could be lost by the British Museum, but lost it was, and for almost 160 years the giant viper of Thessaloniki was all but forgotten. Then, in 2014, a group of researchers announced the discovery of a single partial snake vertebra—barely two centimetres across—at Megalo Emvolon near Thessaloniki in northern Greece. It was about four million years old, and it clearly matched drawings of the lost bones of Owen’s near-mythical viper.
The sediments the bone was preserved in were formed in an ancient lake which, to judge from fossil pollen, was surrounded by sparsely wooded grassland. The fossil fauna discovered alongside the remains of the great snake is reminiscent of that found in the seasonally dry parts of northern India today, including extinct horses, pigs, giant tortoises, a species of monkey, rabbits and a giant peacock.5 Fragmented as the vertebra was, the researchers concluded that Laophis was the largest viper that ever lived. The monster seems to have been closely related to the viper genus (Vipera) that inhabits Europe today, though the largest living Vipera—the horned viper of southern Europe and the Middle East is, at less than a metre long, just one-third its length.
The weight of snakes increases disproportionately with length, and the three-metre-long Laophis is estimated to have weighed 26 kilograms, which makes it more than two and a half times the weight of the king cobra, the largest venomous snake alive today.6 What did this great viper feed on? Today’s horned vipers feed on mammals (mostly rodents), birds and lizards; perhaps Laophis feasted on monkeys, rabbits and giant peacocks. All that we can say with any certainty is that at the dawn of the Pliocene, Europe was home to the greatest venomous snake that has ever existed.
The giant tortoises that shared Laophis’s habitat were also some of the largest that ever lived. Titanochelon was truly stupendous: with shells reaching two metres in length it was the size of a small car. Unique to Europe, these gargantuan chelonians looked like Galapagos tortoises, but were far larger. Giant tortoises need warm conditions, as they can’t burrow as smaller tortoises can. As the ice ages set in, they were restricted to the south of Europe and, as so many other species did, they made their last stand in Spain. The most recent bones, found in an ancient hyena den on a floodplain, are about two million years old.7 And with the giant chelonians went Europe’s last crocodiles and alligators—all carried off by the increasing chill, though it seems possible that the arrival of Homo erectus from Africa might also have played a role in the extinction of the tortoises. After all, the fossil record speaks eloquently of the fact that upright apes and great tortoises don’t mix.
With the cold and the spread of grasslands the bovids flourished. Only two of the nine tribes—the Bovini and Caprini—diversified greatly in Europe.8 The Bovini, which include cattle, bison and buffalo, appear in the European fossil record in the early Pliocene and quickly proliferates. The Caprini, which include goats, sheep and ibex, also diversified during the Pliocene.
Throughout the period, toothy giants persisted in the oceans. Perhaps the most spectacular was the megalodon shark. The largest predator in Earth’s history, it reached lengths of 18 metres and a weight of 70 tonnes. It was named by the Swiss naturalist Louis Agassiz in 1835, who studied some of its enormous teeth, the largest of which are 18 centimetres long and weigh more than a kilogram. The beast had hundreds of them in its jaws and, as befits such a monster, it ate whales. Megalodon’s bite force was between five and ten times greater than that of the great white shark. Gouges are common on the flipper and tail bones of fossil whales, suggesting that megalodon would bite off the locomotor appendages before feeding on the disabled beast. Megalodon evolved early in the Miocene and just kept getting bigger. The very largest individuals lived in the Pliocene—just prior to the species’ extinction about 2.6 million years ago.9
On land, more giants found their way into Europe. After a hiatus of more than 10 million years, elephant migrations recommenced, bringing new species into Europe, while the descendants of earlier migrants declined to extinction. The ancestors of all living African and Asian elephants, as well as the mammoths, originated in Africa towards the end of the Miocene. Mammoths migrated to Europe from Africa around three million years ago and soon gave rise to Mammuthus meridionalis, a species weighing 12 tonnes and adapted to life in Europe’s woodlands.10 A relative of the Indian elephant also arrived in Europe in the late Pliocene, but soon became extinct there, as did Europe’s deinotheres and gompotheres.11
The Pliocene heralded the arrival of Europe’s first modern bears. The Auvergne bear, Ursus minimus, was similar to, but a little smaller than, the Asian black bear. It appears to have given rise to the Etruscan bear (Ursus etruscus), which is so similar to the Asian black bear that some researchers consider them to be one and the same. In a fairytale-like twist, the Etruscan bear gave rise to Europe’s three bears of yore: the brown bear, the cave bear and the polar bear.
I cannot leave the Pliocene without saying vale to those ti
ny and obscure amphibians, the pert’uns. After enduring almost 350 million years, they finally winked out 2.8 million years ago, the last we see of them being some bones preserved in limestone fissures near Verona. Had they survived we would marvel at them as being among the most venerable of Earth’s creatures.
The composition of Europe’s fauna at the time the ice ages set in is something of a mystery; fossil sites are few, and the possibilities of migration were many and varied.12 A rich two-million-year-old fossil deposit in southern Spain offers a window into this ‘lost world’. It has yielded the remains of 32 mammal species, including a primitive kind of muskox (clearly adapted to much warmer conditions than the kind living today) a wolf, a giraffe, the brown hyena and the bush pig, the last two of which are otherwise unknown in Europe, but thrive in Africa today. Analysis of the fossils has allowed Dr Alfonso Arribas and his colleagues to develop a simple hypothesis of migration and, according to Occam’s razor, the simpler the explanation the more likely it is.*
Arribas and his team think that Europe’s early ice age fauna resulted from just one migration event that occurred almost two million years ago, and which took place across islands in what is now the Strait of Gibraltar. Even the Asian species used this route, the researchers argue, after migrating right across north Africa. The theory was challenged just a year after it was articulated, when experts in the evolution of the dog family announced that they had detected the presence of the earliest wolf-like creatures, Canis etruscus, in French fossil deposits dating to around 3.1 million years ago.13 We are, I think, still a long way from a full understanding of the migrations that occurred in Europe on the eve of the ice ages. And only more careful digging will provide the answers.