The Second Book of General Ignorance (23 page)
Read The Second Book of General Ignorance Online
Authors: John Lloyd,John Mitchinson
No, they aren’t blind at all.
Of the 1,100-odd species of bat in the world, not one is sightless – and many can see very well indeed. The notion that bats don’t need eyes because they get about exclusively using echolocation or ‘sonar’ is complete nonsense.
Fruit bats (also called Megabats) don’t use echolocation at all. They have large eyes, which they use both to navigate and
to find their food – which is, as you might expect, fruit. Echolocation isn’t much help in finding food that doesn’t move around. Instead, for fruit-location, they also have a keen sense of smell.
The Common Vampire bat (
Desmodus rotundus
) is the only bat that feeds on the blood of mammals. It is such a very long way from blind that it can see a cow 120 metres (400 feet) away: in pitch darkness, in the middle of the night.
Even microbats – which eat insects and include all British bats, and which
do
use sonar to hunt – use their (much smaller) eyes for avoiding obstacles, for spotting landmarks,and for working out their flying height. Microbats have good night vision. They see in black and white because they’re nocturnal, whereas fruit bats see in colour because they’re active in the daytime.
In the Americas there are several species of ‘fishing bats’, such as the Greater Bulldog bat (
Noctilio leporinus
), which lives by using its keen eyesight and immense feet to drag fish out of the water. It is easily identified, not only by its 66-centimtre (26-inch) wingspan, but also by the repugnant odour of its roosts.
Very few humans find bats palatable but, for special occasions like weddings, the Chamorro people of Guam like to boil giant fruit bats or ‘flying foxes’ in coconut milk and eat them whole – wings, fur and all. This may explain why so many Chamorro suffer from a rare and terrible neurological condition – ALS-Parkinson dementia complex.
The bats feed on poisonous cycad plants, whose dangerous neurotoxins are passed on (now lightly flavoured with coconut) to the unfortunate diners.
Meet the bamboo mite.
Bamboo mites (
Schizotetranychus celarius
) eat bamboo and bamboo alone. They are tiny creatures related to spiders and are only 0.4 mm (1/60 inch) long. They form colonies in dense webs under bamboo leaves and suck the chlorophyll from the leaf cells. This makes the leaves mottled and unsightly and a heavy infestation can kill the plant altogether. The mites live about forty days inside their web, only leaving it to defecate. Radical pruning is the safest way to get rid of them, or you could try importing one of several species of larger, predatory mite to eat them (these cost about 1p each via mail order).
Another parasite that lives uniquely on bamboo is the noxious bamboo mealybug (
Dinoderus ocellaris
). This pest turns the sap of the bamboo into sugary honeydew. This in turn grows a sooty-black mould that looks nasty but which is irresistible to ants. A practical (if fairly slow) way to control bamboo mealybugs is to eat their larvae. In Thailand bamboo borer grubs are a delicacy, often appearing on menus as ‘fried little white babies’.
One animal that
doesn’t
live entirely on bamboo is the Giant panda (
Ailuropoda melanoleuca
). Admittedly, up to 99 per cent of its diet
is
made up of bamboo, but pandas will happily eat small mammals, fish and carrion if they can rouse themselves to catch any.
The problem is that pandas are built like carnivores but eat like herbivores. Bamboo is available all year round, but it’s so low in nutrition that, to satisfy their basic needs, pandas must spend twelve hours a day munching the equivalent of a hay bale of the stuff. This leaves little time (or energy) for hunting or gathering. Nor does it produce enough fat to hibernate in the winter. Instead, it generates a tremendous amount of waste.
Pandas defecate more than forty times a day – excreting about half the weight of what they eat – and their droppings are so fibrous that one Thai zoo uses them to make souvenir paper.
Perhaps because of the endless regime of eating and sleeping, pandas aren’t very sociable. When it comes to defending their territory, they avoid energy-sapping confrontations. Instead, they keep other pandas at bay by marking their boundaries with scent. They do this in four distinct ways, the most unusual being to leave a mark while doing a handstand. The higher the pee, the more dominant the signal is rated by potential rivals. No other animal in the world does this.
As well as keeping the 2,000 surviving wild giant pandas alive, bamboo has other extraordinary qualities. It is the world’s fastest-growing plant: one species in China grows a metre (about 3 feet) a day (that’s nearly 8 centimetres, or 3 inches, an hour) and, when fully grown, can reach 60 metres (200 feet) tall. It also has a ‘bend-factor’ ten times greater than that of steel, making it ideal for construction – almost all the scaffolding in Hong Kong is made of bamboo.
Humans may look less hairy than a chimpanzee, but we have the same number of hair follicles – about 5 million – on our bodies, of which only 100,000 (2 per cent) are on our scalps.
Our hair has evolved to be finer and more transparent than in other primates. We lost our fur, and no one knows why. One theory is that it was to reduce lice. Another is that, when our ancestors moved out of the forests on to the savannah about 1.7 million years ago, we needed to lose body hair to
stop overheating. As we became less hairy, we became darker-skinned to protect our skin from the sun. But that doesn’t explain why the Inuit of the Arctic have less body hair than many sub-Saharan Africans.
Nor does it explain why our scalp hair is programmed to grow for such long periods: left to its own devices, it would grow down past our waists. Other mammalian fur is more like our body hair – it grows to a set length and then is replaced. (Nor can we explain why some men sprout luxuriant hair out of their ears, noses, eyebrows and backs, even as their heads go bald.)
One theory links our loss of fur with increased brain size. A bigger brain creates more heat; in order to keep our temperature under control, we evolved to sweat heavily (sweating is hopeless if you have fur). So, the less fur we had, the more efficient our cooling system became and the bigger our brains grew. Also, as humans walked upright, the only place we still needed hair was on the head, to protect our expanding brains against the sun.
Another more extreme hypothesis suggests we evolved from ‘aquatic apes’. This supposes that 8 million years ago the ancestors of modern humans lived a semi-aquatic lifestyle, foraging for food in shallow waters. As fur is not an effective insulator in water, we evolved to replace it, as other aquatic mammals have, with higher levels of body fat. Unfortunately, there isn’t any fossil evidence for aquatic humans (or apes) at all.
Yet another idea is that hairlessness, once it had started to evolve, was reinforced by sexual selection – in other words it became attractive to the opposite sex. Charles Darwin went along with this (though, given that, it’s odd he chose to have such an enormous beard) and it may be why women are less hairy than men and why smooth, clear skin has become a sign of good health.
Nobody’s really sure, though. As leading palaeoanthropologist Ian Tattersall recently remarked: ‘There are all kinds of notions as to the advantage of hair loss, but they are all just-so stories.’
A lot like us.
The latest reconstructions of Neanderthals look very similar to humans. If you gave one a haircut and a tracksuit, it wouldn’t look out of place on a bus.
The first fossilised remains of humanity’s closest cousins were found in 1856 near Düsseldorf in the Neander river valley, hence the word
Neanderthal (Tal
, then spelt
Thal
, is German for ‘valley’).
Homo neanderthalensis
used tools, wore jewellery, had religious rites, buried his dead and could probably talk. Like us they had the essential hyoid bone (which holds the root of the tongue in place) and recent genetic analysis shows they had exactly the same ‘language gene’ (FOXP2) that humans do. Using the word Neanderthal to mean ‘oafish’ or ‘unreconstructed’ is unfair. In fact, this notion derives from a misinterpretation of the very first reconstruction of a Neanderthal skeleton.
It was the work of a French palaeontologist called Pierre Marcellin Boule (1861–1942) who in 1911 put together a specimen with a curved spine, a stoop, bent knees, and a head and hips that jutted forward. In 1957 the skeleton was reexamined and it became clear that the original owner had suffered from a grossly deforming type of osteoarthritis. Not only did this not represent the average Neanderthal, but Boule had also let his preconceptions affect his work, giving the
skeleton an opposable big toe like a great ape, even though the bones didn’t provide any evidence for such a conclusion.
Neanderthals had barrel-shaped chests and broad, projecting noses – traits some palaeoanthropologists believe helped them breathe better when chasing prey in cold environments. They had bigger brains than modern humans, but they couldn’t run as fast and were shorter and less adept at using tools. What they lacked in height they made up for in strength: Neanderthal females had bigger biceps than the average male human does today.
Humans and Neanderthals diverged into separate species somewhere between 440,000 and 270,000 years ago. Early Neanderthals moved out of Africa into the Middle East and northern Europe much sooner than
Homo sapiens
did, and lived there for four times as long. They became extinct 30,000 years ago (the last recorded Neanderthal community was on Gibraltar), which means that humans and Neanderthals coexisted for at least 12,000 years.
No one knows why the Neanderthals died out. Were they out-competed by humans or did they (for some unknown reason) fail to adapt to the last Ice Age, when Europe became a frozen, sparsely vegetated semi-desert? The oldest known ornaments in Europe (made from shells) were the work of Neanderthals and some researchers now think that humans might have learned ritual and even culture from them during the 120 centuries we shared.
But the most startling fact to emerge from analysis of the genome of the Neanderthals is that they interbred with us. So, unless you are a pure black African, between 1 per cent and 4 per cent of you is Neanderthal.
STEPHEN
How would you spot a Neanderthal if you saw one on a
bus?JACK
DEE
He’d be the one who comes and sits next to me.JO BRAND
He’s the one already sitting next to me,’cause I’m
married to him.STEPHEN
Is this going to be the ‘humiliate my husband’ show?
JO
It’s all right, he doesn’t watch this. He doesn’t really understand
it.
It’s your nose.
It was once impossible to know how our sensory organs evolved because the soft parts of our bodies don’t survive in the fossil record. However, genetic analysis at Cornell University has led ‘sensory psychologist’ Avery Gilbert to believe that the nose is the fastest-evolving human organ.
In mammals the largest single family of genes controls the sense of smell. The study of the human genome shows that ours has altered much more rapidly than those of our closest living relatives, the great apes. This means we sniff less, but taste more, sending aromas from the back of the throat to the nose as we chew. Known as ‘retronasal olfaction’ or ‘back-of-the-nose smelling’ (as opposed to orthonasal smelling through the nostrils) this ability to savour food as we are eating is almost unique to humans. In Avery’s words: ‘The human nose evolved to serve the human mouth.’
Two events may have contributed to this. The first was cooking with fire, first discovered 1.8 million years ago by our
ancestor
Homo erectus
, bringing with it the enticing smells of roast meat and caramelised fruit. The second was the domestication of animals around 15,000 years ago, closely followed by the invention of farming. This brought a whole new range of flavours (yogurt, milk, cheese, bread and toast) and the domestication of the dog gave us a companion species with an extremely acute sense of smell. One theory is that our ancestors delegated the practical scent-tracking function of our noses to dogs, while we concentrated on the ever more complex and delicious aromas coming from the cooking pot. Eating together around the campfire transformed human culture: our shared sense of taste helped to civilise us.