I began this book by imagining a teacher of Latin forced to waste time and energy defending the proposition that the Romans and their language ever existed. Let's return to that thought, and ask what actually is the evidence for the Roman Empire and the Latin language. I live in Britain where, as in the rest of Europe, Rome wrote her signature all over the map, carved her ways into the landscape, wove her language through ours and her history through our literature. Walk the length of Hadrian's Wall, whose preferred local name is still 'The Roman Wall'. Walk, as I walked Sunday after Sunday in crocodile formation from my boarding school in (relatively) new Salisbury, to the Roman flint fort of Old Sarum, and commune with the imagined ghosts of dead legions. Unfold an Ordnance Survey map of England. Wherever you see a long, dead straight country road, especially when there are green field gaps between stretches of road or cart track that you can exactly line up with a ruler, you'll almost always find a Roman label beside it. Vestiges of the Roman Empire are all around us.
Living bodies, too, have their history written all over them. They bristle with the biological equivalent of Roman roads, walls, monuments, potsherds, even ancient inscriptions carved into the living DNA, ready to be deciphered by scholars.
Bristle? Yes, literally. When you are cold, or badly frightened, or haunted by the peerless craftsmanship of a Shakespeare sonnet, you get goosebumps. Why? Because your ancestors were normal mammals with hairs all over, and these were raised or lowered at the behest of sensitive bodily thermostats. Too cold, and the hairs were erected to plump up the layer of insulating trapped air. Too warm, and the coat was flattened to allow body heat to escape more easily. In later evolution, the hair-erection system was hijacked for social communication purposes, and became involved in The Expression of the Emotions, as Darwin was one of the first to appreciate in his book of that name. I can't resist sharing with you some lines - vintage Darwin - from that book:
Mr Sutton, the intelligent keeper in the Zoological Gardens, carefully observed for me the Chimpanzee and Orang; and he states that when they are suddenly frightened, as by a thunderstorm, or when they are made angry, as by being teased, their hair becomes erect. I saw a chimpanzee who was alarmed at the sight of a black coalheaver, and the hair rose all over his body . . . I took a stuffed snake into the monkey-house, and the hair on several of the species instantly became erect . . . When I showed a stuffed snake to a Peccary, the hair rose in a wonderful manner along its back; and so it does with a wild boar when enraged.
The hackles are raised in anger. In fear also, hairs stand on end to increase the body's apparent size and scare off dangerous rivals or predators. Even we naked apes still have the machinery to raise non-existent (or barely-existent) hairs, and we call it goosebumps. The hair-erection machinery is a vestige, a nonfunctional relic of something that did a useful job in our long-dead ancestors. Vestigial hairs are among the many instances of history written all over us. They constitute persuasive evidence that evolution has occurred, and again it comes not from fossils but from modern animals.
As we saw in the previous chapter, where I compared it to a comparably sized fish such as a dorado, you don't have to dig very deep inside a dolphin to uncover its history of life on dry land. Despite its streamlined, fish-like exterior, and despite the fact that it now makes its entire living in the sea and would soon die if beached, a dolphin, but not a dorado, has 'land mammal' woven through its very warp and woof. It has lungs not gills, and will drown like any land animal if prevented from coming up for air, although it can hold its breath for much longer than a land mammal. In all sorts of ways, its air-breathing apparatus is changed to fit its watery world. Instead of breathing through two little nostrils at the end of its nose like any normal land mammal, it has a single nostril in the top of its head, which enables it to breathe while only just breaking the surface. This 'blowhole' has a tight-sealing valve to keep water out, and a wide bore to minimize the time needed for breathing. In an 1845 communication to the Royal Society, which Darwin, as a Fellow, would quite likely have read, Francis Sibson Esq.* wrote: 'The muscles that open and close the blow-hole, and that act upon the various sacs, form one of the most complicated yet most exquisitely adjusted pieces of machinery that either nature or art presents.' The dolphin's blowhole goes to great lengths to correct a problem that would never have arisen at all if only it breathed with gills, like a fish. And many of the details of the blowhole can be seen as corrections to secondary problems that arose when the air intake migrated from the nostrils to the top of the head. A real designer would have planned it in the top of the head in the first place - that's if he hadn't decided to abolish lungs and go for gills anyway. Throughout this chapter, we shall continually find examples of evolution correcting an initial 'mistake' or historical relic by post hoc compensation or tweaking, rather than by going back to the drawing board as a real designer would. In any case, the elaborate and complex gateway to the blowhole is eloquent testimony to the dolphin's remote ancestry on dry land.
In countless other ways, dolphins and whales could be said to have their ancient history written all over and through them, like vestiges of Roman roads drawn out in dead straight cart tracks and bridleways across the map of England. Whales have no hind legs, but there are tiny bones, buried deep inside them, which are the remnants of the pelvic girdle and hind legs of their long-gone walking ancestors. The same is true of the sirenians or sea cows (I've already mentioned them several times: the manatees, dugongs and the 8-yard-long Steller's sea cow, hunted to extinction by humans).* Sirenians are very different from whales and dolphins, but they are the only other group of wholly marine mammals that never come ashore. Where dolphins are fast, actively intelligent carnivores, manatees and dugongs are slow, dreamy herbivores. At the manatee aquarium that I visited in western Florida, for once I didn't rage against the loudspeakers playing music. It was sleepy lagoon music and it seemed so languidly appropriate that all was forgiven. Manatees and dugongs float effortlessly in hydrostatic equilibrium, not by means of a swim bladder as fish do (see below), but through being equipped with heavy bones as a counterweight to the natural buoyancy of their blubber. Their specific gravity is therefore very close to that of water, and they can make fine adjustments to it by pulling in or expanding the rib cage. The precision of their buoyancy control is enhanced by the possession of a separate cavity for each lung: they have two independent diaphragms.
Dolphins and whales, dugongs and manatees give birth to live babies, like all mammals. That habit is not actually peculiar to mammals. Many fish are livebearers, but they do it in a very different way (actually a fascinating variety of very different ways, doubtless independently evolved). The dolphin's placenta is unmistakably mammalian, and so is its habit of suckling the young with milk. Its brain is also beyond question the brain of a mammal, and a very advanced mammal at that. The cerebral cortex of a mammal is a sheet of grey matter, wrapped around the outside of the brain. Getting brainier partly consists in increasing the area of the sheet. This could be done by increasing the total size of the brain, and of the skull that houses it. But there are downsides to having a big skull. It makes it harder to be born, for one thing. As a result, brainy mammals contrive to increase the area of the sheet while staying within limits set by the skull, and they do it by throwing the whole sheet into deep folds and fissures. This is why the human brain looks like a wrinkled walnut; and the brains of dolphins and whales are the only ones to rival those of us apes for wrinkliness. Fish brains don't have wrinkles at all. Indeed, they don't have a cerebral cortex, and the whole brain is tiny compared to a dolphin's or human's. The dolphin's mammalian history is deeply etched into the wrinkled surface of its brain. It's a part of its mammalness, along with the placenta, milk, a four-chambered heart, a lower jaw having only a single bone, warm-bloodedness, and many other specifically mammalian features.
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