Despite their name, not all these animals are purely meat-eaters. The word 'carnivore', like other nouns, can be common or proper. Animals ranging from beetles to buzzards are called carnivores because they eat other animals. Many Carnivores with a capital 'C' do eat meat, but others are omnivores and one, the Giant Panda, is a fairly strict vegetarian. But what distinguishes Carnivores from other mammals is that almost all of them have a set of scissor-like back teeth, called the carnassials, with which to shear through flesh. Some living Carnivores, such as the Giant Panda and the Aardwolf, have lost these scissor teeth, but their ancestors had them. As will become clear in this chapter, the engineering of scissor teeth was the linchpin in the evolution of the Carnivores.

Eating flesh is a luxury. Meat is easier to digest than the much more abundant and easily caught vegetation, and very nourishing. As with most luxuries, though, carnivory can be expensive, making it a high-risk, high-reward lifestyle. Catching prey is both difficult and dangerous. Once caught, converting prey flesh and bone into predator flesh and bone is simpler than the alchemy of turning greenery to flesh. Therefore, flesh specialists, such as the Wildcat and Lynx, have guts only four times their body length. Foxes and wolves, facing the problems of omnivory, have guts five times their body length. Sea Otters, whose digestion has to battle with clam shells, have guts ten times their body length. Bones are difficult to chew and digest, and the Spotted Hyaena's stomach produces copious hydrochloric acid to dissotve them. Cats can vomit voluntarily to rid themselves of piercing stomach aches from bone splinters. Herbivores have a gut pocket, known as a caecum, to digest plants, and this is lacking in flesh-eating Carnivores such as cats, weasels and mongooses. Omnivorous ones, like foxes, have a large caecum. The Eurasian Badger may be disadvantaged because it has become an omnivore, but, like all mustelids, has no caecum.

A Carnivore's diet also affects other aspects of its life, including its sociality. Some foods can be shared, others cannot; some renew within hours, others take years to replenish; some can be attained most effectively by lone animals, others by working in a pack. These differences have led to a diversity of lifestyles, ranging from animals that lead a mainly solitary existence to those whose lives depend on their companions.

Modern Carnivores are split among eight families: the civets and genets (Viverridae, Chapter 1), the cats (Felidae, Chapter 2), the dogs (Canidae, Chapter 3), the hyaenas (Hyaenidae, Chapter 4), the bears (Ursidae, Chapter 5), the raccoons and coatis (Procyonidae, Chapter 5), the weasels, otters, badgers and skunks (Mustelidae, Chapter 6), and the mongooses (Herpestidae, Chapter 7). Today these families include all the top land predators, but in the past they occupied much lowlier positions. The Carnivores have had to fight their way up from the bottom, a 65-million-year contest for the predatory crown.

To find out how the Carnivores came to supremacy we must go back 65 million years to the end of the Cretaceous period. During the Cretaceous, the dominant predators were dinosaurs, a group that also filled many other niches and had done so for 150 million years. If humans had been around at the time, an early dinosaur-watcher might have ducked for cover as a pack of brownish-striped 2-metre (6.5 feet) tall Deinonychus thundered past in pursuit of the graceful vegetarian dinosaur Ornithomimus. The plant-eater would have dodged and swerved to no avail as the 70-kilogram (150-pound) pack hunters fanned out behind it. Dodging one Deinonychus, the exhausted Ornithomimus would have stumbled into another, which kicked out, Kung-fu style, and dragged talon-like hind claws in a disembowelling slash. Deinonychus would then have grasped Ornithomimus in long-fanged jaws and in one vault rolled on its back, pushing out with its forelimbs and kicking with its hindlimbs, like a modern Weasel, to keep the prey's flailing claws at arm's length. An instant later, the pack of Deinonychus would have been on the prey and, after a dismembering struggle, each would have retreated to eat its booty alone.

As in all recreations of prehistoric scenes, one can only speculate. We cannot be certain that Deinonychus hunted in packs, nor that it was partly camouflaged by brownish stripes and killed weasel-style. But the bones of the story are true, because the bones of Deinonychus and Ornithomimus have been preserved as fossils to show that they lived as predator and prey.

Dinosaurs were not all plodding dimwits as often portrayed. Deinonychus was a nimble predator,
and may well have hunted in packs for herbivorous prey like Ornithomimus

The world of 65 million years ago was very unlike that of today. The landscape looked similar to some moderm tropical forests, but the position of the continents was markedly different. There had been one huge continent, Pangaea, and about 136 million years ago this had slowly begun to split up. The shapes of modern continents stIll show how they used to fit together, the east coast of South America snuggling against the west coast of Africa, and Scandinavia locked on to Canada, linked by Baffin Island, Greenland and Iceland. Exactly when, and in which order, the continents split up is controversial, but a popular view is that Pangaea first split into two continents, one northern, Laurasia, and the other southern, Gondwana. Shortly afterwards, just under 130 million years ago, Africa split from the southern continent, followed by India. About 60 million years ago Laurasia split along what is now the North Atlantic, leaving Greenland in the gap. North America and Eurasia drifted apart only to meet on the other side of the world where Alaska and Kamchatka have intermittently been linked by a landbridge across the Bering Straits. By the time of the dinosaurs' demise, Laurasia and Gondwana had drifted far apart and were separated by a wide ocean. For as long as the northern and southern domains remained apart, the story of predatory evolution had two separate strands.

At the time of the dinosaurs' extinction, the southern continent was home to three main groups of mammals One of these, the edentates (the sloths, anteaters and armadillos), had no pretensions to carnivory. Their name, which means toothless, slightly overstates the case for they do have teeth, but simple and often very puny ones. The second group, the didolodonts, comprised only herbivores. It was left to the third group, the pouched mammals or marsupials, to produce the first large mammalian predators in the south. Today, their descendants span creatures from kangaroos to koalas. Marsupials produce young which are extremely premature in comparison with those of the Carnivores, ourselves and other placental mammals. Some, such as the kangaroos, stow their helpless young in pouches while others, such as the opossums, simply plug them unshakably on to their teats.

Marsupials arose in North America before the final breakup of Pangaea. Some spread over Europe and thence to Asia, but by 25 million years ago, marsupials had died out in the northern continent. Others travelled south to Gondwana between 100 and 75 million years ago, and they fared better. There they could roam lands that were to become South America, Antarctica and Australia. The ancestor of the southern marsupial predators was a small creature with a pointed snout, large ears and large eyes. It was probably similar to a small Virginia Opossum, which is a very successful rat-like omnivore in the Americas today. This ancestor was widespread by the time South America split off from the southern continent. Then Australia and Antarctica moved apart, each with its stock of marsupials on board. Drifting south, Antarcfica iced over about 40 million years ago, and fossils of its fauna doubtless lurk deep under the ice. Meanwhile, Australia and South America drifted across the southern oceans as aimless arks for marsupials.

In Australia and South America pouched killers evolved in all shapes and sizes. Until a few million years ago, most of those in South America belonged to a group called the borhyaenids. One of the best fossil records was left by a medium-sized borhyaenid, Cladosictis, 19 million years ago. About 80 centimetres (30 inches) long, Cladosictis looked rather like a modern otter or marten, and lived in Patagonia. Although it was no relation to modern Carnivores, Cladosictis anticipated their invention of pointed canine teeth and molars fashioned as cutting scissors. It probably hunted in water as well as on land, as does the Yapok of the Andes, a member of the modern family of opossums which arose 12 million years ago. The Yapok is the only modern marsupial adapted to a semi-aquatic life. It has webbed hindfeet, and females have a rear-opening pouch which is closed by a sphincter to become a water-tight chamber during a dive. When it arose, the better-adapted Yapok probably competed with Cladosictis for the semi-aquatic trade. Eventially, two million years ago, these borhyaenids were rendered obsolete by modern opossums. Another lineage of pouched killers led to heavily built flat-footed animals that probably ambushed their prey. One was Proborhyaena, known only from part of a skull 60 centimetres (2 feet) long, the same size as that of a modern buffalo.

The pouched killers dominated South America for 30 million years during the Eocene and Oligocene, but about four million years ago many began to face competition from a new breed of predators the phororhacoids, or thunder-birds. Relatives of modern cranes, moorhens and bustards, these flightless birds stood 3 metres (10 feet) tall astride nightmarishly massive legs, and bore mighty curved beaks that were longer than a horse's head. Doubtless the thunder-birds squabbled with vultures of the day for any carrion they came across, but since they lacked the high vantage point used by vultures to locate such food it seems unlikely that they were principally scavengers. It is easy to imagine them pounding in a terrifying sprint, wielding their massive beaks and flailing kicks that could pulverise their prey. They were the closest birds have come to wolves and, at their peak, the thunder-birds may have ousted some wolf-like borhyaenids that chased after prey. Today the thunder-birds have gone, but the crane-like Seriama that still struts the grasslands of South America is a distant offshoot of their lineage.

By about four million years ago the borhyaenids had given rise to a sabre-toothed marsupial killer known as Thylacosmilus or the Pouch-knife, which lived on the pampas of Argentina. It was a stocky animal, much like a modern Leopard in size and build. To out-manoeuvre large prey in open country, the Pouch-knife may have hunted in groups but it was not built for agile pursuit, having massive neck and chest muscles to power-drive its 12.4-centimetre (5-inch) sabres. How it used these weapons to kill is unknown. In 1900, one palaeontologist proposed the charming, if implausible, theory that Pouch-knives used their teeth rather like can-openers on animals called glyptodonts. These were lumbering armadillo-like mammals which invested 20 per cent of their weight in a protective bony shell and a mace-like tail. When faced with a Pouch-knife, a glyptodont would have lowered its defenceless belly to the grass, pulled its head as far into its shell as it would go and twirled its fearsome tail. A lunge from the Pouch-knife would have earned it a swipe from the glyptodont's rapidly thrashing 1-metre (3.3-foot) long mace.

Reconstructing the operation of the Pouch-knife's teeth was held up for years by misleading drawings based on the first Pouch-knife skull to be described, which had been rather distorted by fossilisation. The drawings depicted the sabre canines as diverging, an improbable design that would exert unbearable, jaw-splitting pressure on the animal as its teeth sank in to flesh. It now seems that the Pouch-knife's rapier teeth were parallel. The muscles for lowering its head were immensely strong, probably more so than those of sabre-toothed cats. Furthermore, its upper canines were rather straight, allowing a direct downward thrust to inflict a deep stab wound. So Pouch-knives may have stabbed their prey with a violent downward jerk of the head. The teeth of Pouch-knives grew continuously, unlike those of Carnivores such as sabre-toothed cats. Continuous growth made it impossible to anchor the sabres with a bulbous knob in the jaw as in the cats. Instead, a Pouch-knife's canines were deeply rooted in canals that ran through the skull to a position well behind and above the eyes. As they grew, the canines probably retained their razor edge by being sharpened on a horny pad positioned on two flanges which stuck out from the Pouch-knife's chin. Perhaps the animal drove these flanges into its prey's flanks, for use as pivots dun'ng the stabbing bite. The flanges also served as protective sheaths for the sabres, and prevented the Pouch-knives from stabbing their own chest.

While the pouched killers were consolidating their position as dominant predators in the south, a wide range of creatures competed for this role on the northern landmass. In Asia and North America crocodiles came out of the water to stalk the land about 50 million years ago. One, called Pristichampus, was a hoofed beast with serrated teeth, and probably preyed on early mammals. The killer crocs threatened to evolve a new dynasty of ruling reptiles to take the place of the dinosaurs. But by then the mammals had become too diverse to lapse back into the subjugation their ancestors had endured under the reign of the dinosaurs.

Pristichampus, one of the killer-crocs which evolved under 50 million years ago as heirs apparent to the predatory dinosaurs

Arctocyon, founder of a lineage of marsupials, the bear-dogs, that flourished 60 million years ago

The condylarth 'wolf-sheep' had another heirloom from their ancestors that was to prove a fatal burden: their vegetation-grinding molars never really developed into meat-shearing scissor teeth. Their dental dexterity was limited to gripping and tearing meat off the bones of prey. Thus, most of them were eventually put out of business by two lineages of mammals that independently hit upon the innovation of carnassial scissors. Both can be traced to 60 million years ago, but it took these newcomers a long time to oust the 'wolf-sheep' completely.

The carcass of an Embolotherium would have provided a feast for a gathering of Andrewsarchus 37 million years ago. Andrewsarchus was one of the hoofed predators that dominated the northern continent for 20 million years during the Eocene epoch

Hapalodectes was an otter-like hoofed predator whose aquatic habits were the first step to the evolution of whales.
Though toppled from their predator supremacy, they spawned a remarkeable lineage of descendents: the whales.

Go to chapter 1, section b.