The Second Book of General Ignorance (5 page)

You don’t have to be bleeding for one to track you down.

Sharks have an astonishingly powerful sense of smell. They can detect blood at a concentration of one part in 25 million, the equivalent of a single drop of blood in a 9,000-litre (2,000-gallon) tank of water.

It’s the currents that determine the speed and direction of a smell’s dispersal in water, so sharks swim into the current. If you are bleeding, even slightly, a shark will know. If the current is running at a moderate 3½ kilometres per hour (about 2¼
miles per hour), a shark 400 metres (a quarter of a mile) downstream will smell your blood in seven minutes. Sharks swim at nearly 40 kilometres per hour (25 miles per hour), so one could reach you in sixty seconds. Faster currents make things worse – even allowing for the fact that the shark has more to swim against. In a riptide of 26 kilometres per hour (16 miles per hour), a shark less than half a kilometre (a quarter of a mile) downstream would detect you in a minute and take less than two to reach you – giving you three minutes in total to escape.

Sharks also see very well, but even a short-sighted shark with a bad head cold (not that it happens) would still be able to find you. Sharks have excellent hearing in the lower frequencies and can hear something thrashing about at a distance of half a kilometre (a third of a mile). So you could try being very quiet indeed.

A blind, stone-deaf shark with no nose would still find you without breaking stride. Sharks’ heads are riddled with jelly-filled canals by the name of the ‘ampullae of Lorenzini’ after Stefano Lorenzini, the Italian doctor who first described them in 1678. We’ve only recently discovered what their purpose is: to register the faint electrical fields generated by all living bodies.

So, as long as you’re not bleeding, not moving and your brain and heart aren’t working, you should be fine.

And there’s some more good news – sort of. Californian oceanography professor Dr Jamie MacMahan has found that the standard view of a riptide is wrong – it doesn’t run out to sea but is circular, like a whirlpool. If you swim parallel to the shore, he says, there’s a 50 per cent chance you’ll be swept out into the ocean deeps. But, if you just tread water, there’s a 90 per cent chance of being returned to shore within three minutes – perhaps just in time to escape the shark.

If a shark does find you, try turning it upside down and tickling its tummy. It will enter a reflex state known as ‘tonic
immobility’ and float motionless as if hypnotised. Killer whales exploit this by flipping sharks over on to their backs and holding them immobile in the water until they suffocate. You have about fifteen minutes before the shark gets wise to your ruse. Careful, though: not all species of shark react the same way. Tiger sharks, for example, respond best to a gentle massage around the eyes. According to shark expert Michael Rutzen, it’s just like tickling trout: ‘All you have to do is defend your own personal space and stay calm.’

Having said all this, relax. Sharks almost never attack people. Figures from all twenty-two US coastal states, averaged over the last fifty years, show that you are seventy-six times more likely to be killed by a bolt of lightning than by a shark.

Yes it does, despite what every tour guide tells you.

Most of them are very small: just a few centimetres back and forth on average. This is because the Mediterranean is cut off from the Atlantic (and the huge effect of the pull of the moon on it) by the narrow Straits of Gibraltar.

Right next door to the entrance to the Med, sea levels can change by around 80 centimetres (3 feet) but in the Gulf of Gabes off the coast of eastern Tunisia, the tidal elevation can be as much as 2.5 metres (8 feet) twice a day.

This is because tides are caused not only by the gravitational effect of the moon but also by atmospheric pressure, depth, salinity, temperature and the shape of the coastline.

The relatively big tides in the Gulf of Gabes result from its shape. It is a wide, shallow basin, about 100 kilometres (60 miles) wide by 100 kilometres long. The gulf acts as a funnel,
the tidal energy forcing water into a progressively smaller space, thereby increasing the rise in sea level – and, correspondingly, lowering it on the way out. The same thing happens on a much greater scale in the Bristol Channel, which has a tidal range of over 9 metres (30 feet).

Tidal effects are at their strongest when the sun and moon are on the same side of the earth (new moon), or on the opposite side (full moon), and their gravitational pulls combine to create the strong ‘spring’ tides (‘spring’ in the sense of ‘powerful forward movement’, not the season).

The Phoenicians founded Gabes in about 800 bc. Pliny the Elder first noted its unusually large tides in
AD
77 in his
Natural History
. He also recorded that Gabes was second only to Tyre in the production of the expensive purple dye made from murex shells, which the Phoenicians discovered (hence the Greek for purple,
phoinikeos
), and which was highly prized by the Romans: the
toga purpurea
was worn only by kings, generals in triumph and emperors.

The Mediterranean is bigger than you might think. At 2,500 square kilometres (965 square miles) it covers the same area as Sudan, the largest country in Africa, and would comfortably swallow Western Europe (France, Spain, Germany, Italy, Greece, Britain, the Netherlands, Belgium, Switzerland and Austria combined). Its coastline stretches for 46,000 kilometres (28,000 miles) or about twice the length of the coastline of Africa. Nor is it particularly shallow: its average depth is over 1½ kilometres (about a mile) while the North Sea’s is a mere 94 metres (310 feet) and, at its deepest point, in the Ionian Sea, it reaches down nearly 5 kilometres (over 3 miles), substantially deeper than the average depth of the Atlantic.

Six million years ago, the Mediterranean dried out completely in the so-called Messinian Salinity Crisis. This created the largest salt basin that ever existed and raised the sea level of the rest of the world by 10 metres (33 feet). Three
hundred thousand years later, the rock barrier at the Straits of Gibraltar gave way – in a cataclysm called the Zanclean Flood – producing the world’s largest-ever waterfall and refilling the whole of the Mediterranean in as little as two years. The tide would have risen 10 metres every day. But it wouldn’t have gone out again.

Many smart people would answer ‘finches’, but actually it was mockingbirds.

The great passion of the young Charles Darwin (1809–82) was killing wildlife. As a student at Cambridge, when the shooting season started, his hands shook so much with excitement he could hardly load his gun. Though studying medicine and divinity to please his father, he dismissed lectures as ‘cold, breakfastless hours, listening to discourses on the properties of rhubarb’.

But he was also an enthusiastic amateur biologist and fossil-hunter and was keen to see the tropics, so he signed on as a ‘gentleman naturalist’ for HMS
Beagle
’s second survey expedition (1831–6). He almost didn’t get the job: the captain was keen on physiognomy and thought that Darwin’s nose indicated laziness. Charles later noted that ‘I think he was afterwards well satisfied that my nose had spoken falsely’.

The story goes that, during the voyage, Darwin noticed that finches on different islands in the Galapagos had distinctive beaks, which led him to guess that each type had adapted for a specific habitat and evolved from a common ancestor. It’s true that Darwin’s theory of evolution by natural selection originated aboard the
Beagle
, but it had nothing to do with finches. Though Darwin did collect finch specimens from the Galapagos, he showed very little interest in them until years later. He was no ornithologist in those days and wasn’t even aware that the finches were of different species. It wouldn’t have helped much if he had been, because he didn’t label them to show where they’d been caught. He mentioned them only in passing in his journals and they are not mentioned once in
On the Origin of Species
(1859).

The mockingbirds were a different matter. Intrigued by the variations between the populations on two nearby islands, Darwin took careful note of every mockingbird he encountered. Gradually, as his journals show, he began to realise that species were not immutable: they could change over time. Out of that insight all his subsequent theories on evolution grew.

Because the finches are a perfect example of Darwin’s theories in action, later scientists assumed that they must have been the birds that inspired him. One of these was the evolutionary biologist David Lack (1910–73) whose 1947 book,
Darwin’s Finches,
fixed the idea (and the term) in the popular consciousness.

Darwin’s book on the voyage of the
Beagle
was an immediate best-seller, and the trip made the captain’s name too. Robert Fitzroy (1805–65) went on to become a vice-admiral, Governor General of New Zealand and the inventor of weather forecasting – one of the sea areas in the Shipping Forecast is named after him.

The finches got famous, too, as we know. The fifteen species of
Geospizinae
are still popularly known today as Darwin’s Finches – although it turns out they’re not finches at all, but a different kind of bird called a tanager.

In your own back garden.

You can cancel that expensive (and possibly dangerous) trip up the Amazon.

In 1972 an ecologist called Jennifer Owen started to note down all the wildlife in her garden in Humberstone, a suburb of Leicester. After fifteen years she wrote a book about it. She had counted 422 species of plant and 1,757 species of animal, including 533 species of parasitic Ichneumon wasp. Fifteen of these had never been recorded in Britain, and four were completely new to science.

Suburban gardens cover 433,000 hectares (well over a million acres) of England and Wales. If so many new species can be found in just one of them, this must be true of others. Between 2000 and 2007, the Biodiversity in Urban Gardens in Sheffield project (BUGS) repeated Dr Owen’s work on a bigger scale. Domestic gardens account for some 23 per cent of urban Sheffield, including 25,000 ponds, 45,000 nest
boxes, 50,000 compost heaps and 360,000 trees. These present, as Professor Kevin Gaston, BUGS’ chief investigator, put it ‘175,000 separate conservation opportunities’. One of BUGS’ discoveries was what may be a new, minuscule species of lichen, found in the moss on an ordinary tarmac path.

To more or less guarantee discovering a new species, all you need is a garden, a lot of time and patience, and a lot of expertise. In the words of the eighteenth-century naturalist Gilbert White (1720–93), ‘In zoology as it is in botany: all nature is so full, that that district produces the greatest variety which is the most examined.’ In 2010 London’s Natural History Museum found a new species of insect in its own garden. They are baffled by what it is, as it doesn’t match any of the more than 28 million specimens inside the museum itself.

Part of the fun of discovering a new species is that you get the chance to choose what it’s called. A recently discovered beetle with legs resembling overdeveloped human biceps was named
Agra schwarzeneggeri
; a fossilized trilobite with an hourglass-shaped shell was called
Norasaphus monroeae
after Marilyn Monroe; and
Orectochilus orbisonorum
is a whirligig beetle dedicated to singer Ray Orbison because it looks like it’s wearing a tuxedo. In 1982 Ferdinando Boero, now a professor at Lecce University in Italy, but then a researcher at Genoa, had a more underhand motive in naming the jellyfish he discovered
Phialella zappai
– it was a cunning plan to persuade his hero Frank Zappa to meet him. It worked: they remained friends for the rest of the musician’s life.

British-born astrobiologist Paul Davies of Arizona State University urges us all to search for new unknown forms of life. ‘It could be right in front of our noses – or even in our noses,’ he says.

The one thing you don’t want to find in your nose is an Ichneumon wasp. These unpleasant insects caused Darwin to
lose his religious faith. ‘I cannot persuade myself’, he wrote, ‘that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars.’

Before you answer, bear in mind that
Rattus rattus
is a rat,
Gerbillus gerbillus
is a gerbil,
Oriolus oriolus
is an oriole,
Iguana
iguana
is an iguana,
Conger conger
is a conger eel and
Gorilla
gorilla gorilla
is emphatically a gorilla.

And
Puffinus puffinus
?

Bad luck, that’s the Manx shearwater. It’s unrelated to the puffin.

Scientific names for animals are usually composed of two words: the genus comes first, followed by the species. The species of a living thing is defined as that group with which it can reproduce. Its genus is analogous to its tribe: a group of species that are clearly related to each other. When the names of an animal’s genus and its species are the same that’s called a tautonym (from the Greek
tautos
‘same’ and
onoma
‘name’). For example, the bogue fish is
Boops boops
and
Mops mops
is the Malayan Free-tailed bat.

Where there is a third part to the name of a species, it is used to indicate a subspecies. So the triple tautonym
Gorilla
gorilla gorilla
(the Western Lowland gorilla) is a subspecies of
Gorilla gorilla
(the Western gorilla). The Tiger beetle subspecies
Megacephala (Megacephala) megacephala
has a name that translates as ‘bighead (bighead) bighead’. Sometimes a subgenus is also given in brackets such as
Bison (Bison) bison
bison
, which (for the avoidance of doubt) is a kind of bison.

Tautonyms for animals are not uncommon, but are strictly forbidden for plants under the International Code of Botanical Nomenclature.

There are three species of puffin and they belong to the genus
Fratercula
, Latin for ‘little brother’, because their plumage resembles monastic robes.

There are about thirty species of shearwater, all of which share the genus name
Puffinus
, which comes from an Anglo-Norman word meaning ‘fatling’. This refers to the chubbiness of the young birds, and hints at their culinary uses. They were eaten both fresh and pickled and, because they swim so well under water, were for a long time thought to be half fish, which allowed Catholics to eat them on Fridays and during Lent. Shearwater chicks are easily mistaken for puffins: which probably explains the confusion over the name. Puffins (and particularly their hearts) are a national delicacy in Iceland.

The oldest living bird ever recorded in Britain was a Manx Shearwater. It was found by chance in 2002 by the staff of the bird observatory on Bardsey Island in North Wales. They were delighted to discover that ornithologists had ringed it in 1957, when it must already have been at least five years old. It’s reckoned to have covered around 8 million kilometres (5 million miles) over more than half a century, flying to South America in the winter and back again to Britain for the
Puffinus
puffinus
breeding season.