Europe

by Tim Flannery

  I suspect that this preponderant migration from north to south is due to the greater extent of land in the north, and to the northern forms having existed in their own homes in greater numbers, and having consequently been advanced through natural selection and competition to a higher stage of perfection, or dominating power, than the southern forms.1

  Most of Europe’s core fauna is now long extinct, but there are a few unlikely survivors. The most important are the alytids (the family that includes the midwife toads) and the typical salamanders and newts (family Salamandridae). These relics of Europe’s dawning are deserving of special recognition, for they are in effect Europe’s living fossils, as precious as the platypus and lungfish.

  In March 2017, I visited Voltaire’s estate in Ferney-Voltaire, near Geneva. The first flowers of spring were showing through on the south-facing slopes, but the woodland was still wet and winter-cold. I turned a log and saw under it a brown creature, barely 10 centimetres long, its only colour at this non-breeding time the slightest hint of an orange stripe running down its back. It was an Italian crested newt (Triturus carnifex), which within weeks would enter a pond and, if male, sprout an extravagant dragon-like crest, bright spots and vivid black-and-white facial markings.

  The creature belongs to the family Salamandridae, whose 77 species are distributed across North America, Europe and Asia. This wide distribution has long obscured their point of origin, but a study of mitochondrial DNA from 44 species has revealed that the salamandrids first evolved about 90 million years ago on an island in the European archipelago.2 Perhaps it was Meseta, where the oldest salamandrid fossils on Earth have been discovered. The study also revealed that the gloriously colourful Italian spectacled salamanders diverged from the rest of the salamandrid family while the dinosaurs still lived. Just after the dinosaur extinction, salamandrids reached North America and gave rise to the North American and Pacific newts. Even later, around 29 million years ago, some salamandrids reached Asia, and they in turn gave rise to the fire-bellied newts, paddle-tailed newts, and other Asian types.3

  It is humbling indeed to realise that the ancestors of that tiny, fragile creature I had seen lurking in the depths of Redmond O’Hanlon’s pond in Oxfordshire are part of a group that colonised the Americas from Europe long before Columbus, and east Asia well before Marco Polo. To me they, rather than some empire-building human coloniser, are the real embodiment of European success.

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  * Among those so restricted were the now-extinct solemydid turtles and the lake-dwelling palaeobatrachid frogs, which were restricted to Gaelia, as was the giant flightless bird Gargantuavis and the flesh-eating dinosaurs known as abelosaurids, a kind of salamander, possibly strange burrowing lizards known as amphisbaenids, and relatives of the glass lizards (which originated in North America). Bajazid’s lovely round turtle and the terrifying Hatzegopteryx in contrast, were unique to Hateg, while the python-like matsoiine snakes, with their rudimentary limbs were only found on islands in the east and west of the European archipelago, but not in the middle.

  CHAPTER 6

  The Midwife Toad

  It is a truth that sounds more like a fairytale that a toad lies at the heart of ancient Europe.* Today, the common midwife toad can be found from the lowlands of southern Belgium to the sandy wastes of Spain, making it the most successful and widely distributed member of Europe’s oldest surviving vertebrate family, the Alytidae, a group comprising the midwife toads, the disc-tongued frogs, the firebellies and the painted frogs.** Look a midwife toad in the eyes, and you are looking at a European whose ancestors blinked at the terrible Hatzegopteryx, and one that has survived every catastrophe that has rocked the world over the past 100 million years. More venerable, and more distinctly European than any other creatures, the alytids are living fossils that should be considered nature’s nobility.

  Some alytids are diligent fathers—which has doubtless aided their survival. When midwife toads mate, the male gathers up the eggs and winds strands of them around his legs. He can mate up to three times per season, so some individuals carry three broods in this manner. For up to eight weeks the male carefully tends the eggs, carrying them everywhere he goes, wetting them if they are in danger of drying out, and secreting natural antibiotics from his skin to protect them from infection. When he senses that they are about to hatch, he seeks out a cool, calm pond for the tadpoles to grow in.

  There are five species of midwife toad: the widespread nominotypical species, three restricted to Spain and its islands, and one that reached Morocco from Spain in the recent geological past. The Majorcan midwife toad has the distinction of being a Lazarus species, being first described from fossils.* It was widespread on Majorca prior to the arrival of humans, but when mice, rats and other predators reached the island the toads vanished. A few survived, undetected, in the deep valleys of the Serra de Tramuntana, and following their discovery in the 1980s they were reintroduced into various parts of the island, where, with a little protection, they are once again thriving.1

  Midwife toads played a crucial role in an all-but-forgotten scientific debate in the early twentieth century between English statistician and biologist William Bateson—the man who coined the term ‘genetics’—and Professor Richard Semon and his colleagues, who argued for non-genetic inheritance via a Lamarckian form of cellular ‘memory’.2

  Richard Semon was a formidable intellect. Born in Berlin in 1859, he spent much of his youth in the wilds of colonial Australia, collecting biological specimens and living with the Australian Aborigines. Upon his return to Germany he studied how ideas and traits are passed from one individual to another. His book The Mneme, published in 1904, was a foundation work on the subject, and its influence was destined to be felt far beyond biology. It commences with the observation:

  The attempt to discover analogies between the various organic phenomena of reproduction is by no means new. It would be strange if philosophers and naturalists had not been struck by the similarity existing between the reproduction in offspring of the shape and other characteristics of parent organisms, and that other kind of reproduction we call memory.

  In trying to explain his concept, Semon reminisces:

  We were once standing by the Bay of Naples and saw Capri lying before us; nearby an organ-grinder played on a large barrel-organ; a peculiar smell of oil reached us from a neighbouring ‘trattoria’; the sun was beating pitilessly on our backs; and our boots, in which we had been tramping about for hours, pinched us. Many years after, a similar smell of oil ecphorised [brought to mind] most vividly the optic engram [memory] of Capri. The melody of the barrel-organ, the heat of the sun, the discomfort of the boots, are ecphorised neither by the smell of the oil nor by the renewed experience of Capri…This Mnemic property may be regarded from a purely physiological point of view, in as much as it is traced back to the effect of stimuli applied to the irritable organic substance.3

  This was true, according to Semon, regardless of whether the mneme was a memory or an inherited aspect of a body such as eye colour.

  British–German rivalry and the horrors of World War I meant that Semon’s book was not translated into English until 1921, too late for its author. A great nationalist, he felt the defeat and shame of surrender so acutely that he wrapped himself in the German flag and shot himself. Today, Semon is not entirely forgotten. A skink discovered living on the island of New Guinea bears his name. Prasinohaema semoni’s most distinctive attribute is that its blood is bright green.

  After Semon’s death, his work was continued at Vienna University by a team including the brilliant young scientist Paul Kammerer, who was a student of music before he turned to biology. His experiments look bizarre by modern standards but were considered the height of scientific elegance at the time. His greatest triumphs involved manipulating the love life of the ‘obstetric toad’ (the common midwife toad). Toiling over hundreds of the warty creatures, he persuaded them to forgo their predilection for having sex on
land.

  Aquatic copulation was finally achieved by keeping them ‘in a room at high temperature…until they were induced to cool themselves in a water trough…here the male and female found each other…’ and, Kammerer reported, mated in the normal anuran* manner (where the female releases the eggs into the water, where they are fertilised), rather than in the manner of midwife toads (where the male helps squeeze the eggs from the female, then wraps them around his hind limbs). This was interpreted as the toad ‘remembering’ the ancestral way of having sex—a trait, it was claimed, which persisted in subsequent generations. The male descendants of midwife toads that mated in water, Kammerer said, even grew a special black wart on their palms that they used to grasp the wet and slippery female—a feature seen in many frogs and toads, but which has been lost in the midwife toads.

  Even after producing such astonishing ‘proofs’ of Semon’s mnemic theory, the amphibians in Kammerer’s lab were allowed no rest. In a separate experiment, Dr Hans Spemann forced the bombinator (firebelly) toad* to grow eye lenses on the back of its head—a remarkable feat, but one that was surpassed by Gunna-Ekman, who induced green tree frogs (Hyla arborea) to grow eye lenses anywhere on the body ‘with the possible exception of the ear and nose’. This, it was argued, proved that the frog’s skin ‘remembered’ how to grow eyes—if appropriately stimulated. Meanwhile, Walter Finkler devoted himself to transplanting the heads of male insects onto the bodies of females. The hybrid creatures showed signs of life for several days, but, perhaps not surprisingly, exhibited disturbed sexual behaviour.

  By the 1920s Kammerer’s work was under severe assault, for it flew in the face of the ‘neo-Darwinian orthodoxy’, then being championed by William Bateson, who was described, when young, as ‘snobbish, racist and intensely patriotic’.4 Bateson’s attacks on Kammerer were, according to Arthur Koestler, vitriolic and obsessive. Bateson suspected fraud from an early stage, and fraud, indeed, was proved in 1926, when it was discovered that the pigmented wart on the palms of one of Kammerer’s midwife toads had been tattooed onto the skin. To this day, the perpetrator of the fraud remains unknown, but it may have been an assistant who was a Nazi sympathiser trying to discredit Kammerer, who was a Jew, an ardent pacifist and a socialist. The fraud was held up by Bateson as evidence that Kammerer’s life’s work was suspect and, with his reputation in tatters, Kammerer took a walk in a forest and—like Semon before him—shot himself.

  In 2009, the developmental biologist Alexandre Vargas re-examined Kammerer’s findings and claimed that, beyond the tattooed toad palm, they may not have been fraudulent, but could be explained by epigenetics—changes caused by the modification of gene expression, rather than alteration of the gene itself. Other researchers have claimed that Kammerer should be credited as the founder of the epigenetic phenomena known as ‘parent of origin’ effects, whereby genetic imprinting allows the silencing of certain genes. A century after their suicidal despair, both Kammerer and Semon are gaining some recognition.

  The midwife toads have a close relative in Europe in the firebelly or ‘bombinator’ toads (the same creatures that Hans Spemann manipulated to grow eye lenses on the backs of their heads). There are eight species of these small but colourful amphibians, and they are the only real travellers among the alytids.* Tens of millions of years ago, these tiny firebellies managed to cross the entire breadth of the Eurasian landmass, and today five of the eight species inhabit mountains and swamps in China.

  The alytids are one of just three ancient frog families in the order Archaeobatrachia—the most primitive frogs and toads surviving today. The other two are New Zealand’s frogs, and the tailed frogs of the North America’s Rocky Mountains. Combined, these two families contain just five species, while the alytids include about 20 living species, over half of which inhabit Europe. The alytids include six species of disc-tongued frogs, two of which have reached North Africa, and the painted frogs (Latonia), of which there is but a single living species. Between 30 million and one million years ago painted frogs abounded in Europe, but then they became extinct. In 1940 biologists collected two adult frogs and two tadpoles in the vicinity of Lake Hula, in what is now Israel. To everyone’s astonishment, they were painted frogs. The larger of the two promptly ate its smaller companion, and in 1943 the cannibal—by then pickled in preserving fluid in a university collection, was pronounced a new species, the Hula painted frog.

  One more painted frog was collected in 1955, but after that the creatures vanished, and by 1996 the International Union for the Conservation of Nature presumed them to be extinct. Israel, however, continued to list the species as endangered. Its faith was repaid in 2011 when a living painted frog was located by ranger Yoram Malka in the Hula Nature Reserve in northern Israel, where a population of several hundred survives. The Hula painted frog is the ultimate Lazarus taxon: thought extinct for a million years, it was discovered clinging to life in a swamp on Europe’s periphery.

  Until half a million years ago, the alytids shared Europe with another group of amphibians, the palaeobatrachids.5 Frogs generally do not make good fossils, but the palaeobatrachids are an exception, and you can see their exquisitely preserved remains on exhibition in many European museums. In habits and body shape, the palaeobatrachids resembled the grotesque clawed frogs of Africa and the Surinam toads of South America, and like them seem to have lived their entire lives underwater, with a preference for lakes, including deep, still ones where the chances of having been preserved as a fossil are far better than for those living in swamps or on land. We missed out on seeing these frogs in the flesh by the merest whisker of geological time.

  This Europe of ‘in the beginning’ may seem like a distant place, with more in common with, say, Australasia than with the Europe of today, but even at this early stage there are some threads that link it with the Europe of more recent times. One is its extremely diverse nature. In the beginning, it was the great lumbering reptiles that differed across the European islands. Today it is distinct languages and human cultures that exist within and across various boundaries. But, just as importantly, then as today, Europe was a land of exceptional dynamism and large-scale immigration—of species that would arrive and find a place among Europe’s existing inhabitants, adapt to local conditions and help make Europe anew.

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  * Strictly speaking, the term toad should be restricted to members of the family Bufonidae, of which the common European and natterjack toads are good examples. But common parlance has seen the name applied to any warty tail-less amphibian.

  ** It is frustrating that both the Asian newts and Asian toads are known as firebellies. Though both firebellies raise an interesting evolutionary question. Why should European colonisers of Asia develop such spectacularly coloured underparts?

  * The term ‘Lazarus species’ was coined by the palaeontologist David Jablonski to describe a taxon that was thought to have gone extinct during a mass extinction event, but which is found to exist several million years later.

  * Anurans are amphibians without tails—the frogs and toads.

  * ‘Bombinator’ refers to the bumble bee, whose humming flight noise is said to resemble the croaking of this most unusual toad. Its call, incidentally, is produced with an inward rush of air, as opposed to the outwards push used by most other frogs and toads.

  * Their position in the family Alytidae is still debated, with some researchers placing them in their own family, the Bombinatoridae. Nobody doubts, however, that they are close relatives of the alytids.

  CHAPTER 7

  The Great Catastrophe

  In a thick sandstone layer in the Tremp Basin in the southern Pyrenees, a ghostly shadow of Europe’s last dinosaurs can be seen—in the form of footprints.* Because the rocks preserving them have been lifted, folded and eroded from below, many footprints are preserved in the roofs of overhangs, so that what we see is a great stony replica of the dinosaur’s foot, stomping down on us from above.1 The prints were mostly m
ade by long-necked sauropods and bipedal hadrosaurs which had migrated into the archipelago from North America and Asia towards the end of the age of dinosaurs. Where they were going, and where they came from on that particular day, nobody knows. But we do know that within 300,000 years of the prints being made the descendants of the creatures that made them would be swept off the face of the Earth. Rare evidence of the cataclysm that destroyed them is preserved in the rocks of the Tremp Basin, where a succession of sediments accumulated unbroken over a long period both before and after the extinction event.