The Lion in the Living Room Chapter 1 CATACOMBS BUBBLING AWAY on Wilshire Boulevard in the middle of downtown Los Angeles, the La Brea Tar Pits look like pools of toxic black taffy. California colonists once harvested tar here to waterproof their roofs, but today these asphalt seeps are far more precious to paleontologists studying Ice Age wildlife. All kinds of fantastic animals mired themselves in the sticky death traps: Columbian mammoths with pretzeled tusks, extinct camels, errant eagles. But most famous of all are the La Brea cats. At least seven types of prehistoric feline inhabited Beverly Hills 11,000 years ago and earlier: close relatives of modern bobcats and mountain lions but also several vanished species. More than 2,000 skeletons of Smilodon populator--the biggest and scariest of the saber-tooth cats--have been recovered from the 23-acre excavation site, making it the largest such trove on the planet. It''s late morning. The asphalt is softening as the day warms and the air smells like melting pavement.

Ugly black bubbles popping on the tar pits'' surface make it look as though a monster is breathing just beneath. My eyes water a bit from the fumes and, plunging a stick into the goo, I find that I can''t pull it out. "You only need an inch or two to immobilize a horse," says John Harris, chief curator of the museum here. "A giant sloth would get stuck like a fly on flypaper." There''s a touch of pride in his voice. The only way to get the asphalt off your skin is to massage it with mineral oil or butter, as a few local fraternity pranksters have learned the hard way. Given time enough, the tar even seeps into bone, preserving the remains of the giant animals that died in agony here so well that pit specimens aren''t even truly turned-to-stone fossils. Drilling into a preserved saber-tooth rib produces the same smell you get at the dentist''s office: burning collagen.

It smells alive. In the murk of the tar pits, I''m searching for clues to the primordial human-feline relationship. Human patronage of cats, which seems so intuitive to us, is in reality a quite recent and radical arrangement. Though we''ve shared the earth for millions of years, the cat family and mankind have never gotten along before, much less gotten cozy on the couch. Our competing needs for meat and space make us natural enemies. Far from sharing food, humans and felines have spent most of our long mutual history snatching each other''s meals and masticating each other''s mangled remains--though to be perfectly honest, mostly they ate us. It was cats like the La Brea saber-tooths, colossal cheetahs, and giant cave lions--and later their modern-day heirs--that dominated the untamed planet. Our prehistoric forebears shared habitats with these sorts of behemoths in parts of the Americas, and in Africa we tangled with various species of saber-tooths for millions of years.

So powerful was the ancient feline influence that cats may have helped make us human in the first place. In a storage room, Harris shows off the milk teeth of a Smilodon kitten. They are almost four inches long. "How did they nurse?" I ask. "Very carefully," he answers. The adult upper canine teeth are eight inches; their shape reminds me of a reaper''s blade. I run my finger along the serrated inner curve and get the chills. Scientists still don''t know much about these animals--researchers once made a steel model of saber-tooth jaws in an effort to figure out how in the world they chewed, and "we only recently learned to tell male from female," Harris admits--but it''s safe to say they would have been absolutely terrifying.

Weighing about 400 pounds, they likely used their burly forelimbs to wrestle down mastodons before stabbing their saber teeth through the thick skin of the prey animals'' necks. Then my eyes stray to a nearby skeleton of an American lion, which stood a head taller than the saber-tooths and probably weighed about 800 pounds enfleshed. So this is what our ancestors were up against. The sheer awesomeness of such predators, and the grisly legacy of our interactions with them, make it especially remarkable that today people are on the cusp of wiping the cat family off the face of the earth. Most modern cat species, big and small, are now in grave decline, losing ground to humans daily. With one exception, that is. Harris marches me out to an ongoing pit excavation near one of the oozing seeps not far from the museum''s door. As two women in tar-smudged T-shirts chip away at a Smilodon femur, there''s a sudden brownish blur around my ankles, and up hops Bob, a tailless female house cat with a potbelly and a proprietary air.

The giggling excavators tell me how they rescued her from the traffic accident in which she forfeited her tail and then nursed her back to health. "No more surprise mice," one woman says, patting Bob''s amputated rump. Which is stranger, I wonder: the fact that Beverly Hills is a graveyard for giant local lions, or that a tiny, unassuming feline stowaway originally from the Middle East thrives here today? But in fact, the house cat''s rise is the flip side of the lion''s ruin. The story of the cat family''s ongoing downfall helps explain what organisms like Bob and Cheetoh and all of our beloved house cats really are: fully loaded feline predators, like lynx or jaguars or any other kind of cat, but also extreme biological outliers. Absent human civilization, the Greater Los Angeles area could still be a prime habitat for the native cats that survived the Ice Age. A few straggling mountain lions continue to haunt the Santa Monica Mountains, though the population is hopelessly isolated and inbred and the rare kittens often end up as highway roadkill. A mountain lion known as P-22 was recently photographed loitering in the hills beneath the Hollywood sign, and gazing out over the glowing city at night. But it''s Bob who rules the tar pits now.

The La Brea saber-tooths and giant lions died out around the end of the last Ice Age for unknown reasons. But we can piece together the narrative of why most of the surviving wild cats--even the smaller species, some of which look very much like our beloved house pets--are in dire trouble today. The story begins where so many of our ancestors ended: inside the mouth of a cat. The cat family is part of the mammalian order Carnivora, the "flesh devourers." All carnivores, from wolves to hyenas, eat flesh as part of their diet, and why wouldn''t they? Meat is a precious resource, full of fat and protein and wonderfully easy to digest. But it''s also hard to come by, and so most animals, including almost all of those classified as carnivores, pad their diets with other food groups. In the bear family, for instance, black bears chomp acorns and tubers with plant-crushing molars that wouldn''t look out of place in the mouth of a cow; pandas famously subsist on bamboo; and even the big-fanged polar bear occasionally munches on berries. Not cats.

From the two-pound rusty-spotted cat to the 600-pound Siberian tiger, all three dozen or so cat species are what biologists call hypercarnivores. They eat pretty much nothing but meat. The plant-chewing molars of cats have shrunk to a vestigial size, like something a child would leave for the tooth fairy, and the rest of their teeth are extremely tall and sharp, a mix of steak knives and scissors. (The difference between a cat''s teeth and a bear''s is like the Alps versus the Appalachians.) Though called canines, the killing teeth at the front of the mouth are actually larger in cats than in dogs, which should come as no surprise: cats require three times as much protein in their diets as dogs, and kittens need four times as much. Dogs can even get by on a vegan diet, but cats can''t synthesize key fatty acids on their own--they must get them from other animals'' bodies. The singular purpose of a cat''s teeth--butchery--explains why all cat maws look alike, even to biologists. The jaws of an insect-sucking sun bear look nothing like a grizzly''s, but sometimes even experts can''t tell a lion''s from a tiger''s because they are designed for exactly the same job.

So it goes for the rest of cats'' bodies. There are tremendous, almost comic differences in body size--some cats are 14 inches long from tip to tail, and some are 14 feet--but very few differences in form. "The important thing about big cats and small cats is not that they are different but that they are the same," Elizabeth Marshall Thomas writes in The Tribe of the Tiger, her history of the feline family. House cats and tigers, she says, are "the alpha and omega of their kind." Sure, tigers have stripes, lions have manes, and pumas have eight nipples while margays have two. But the blueprint endures: long legs, powerful forelimbs, flexible spine, a tail (sometimes up to half the length of the body) for balance, and short guts for digesting meat and meat alone. Cats are armed with retractable claws, sentient whiskers, and ears that rotate for uncanny directional hearing and the broadest possible auditory range. With eyes located at the front of the face, they possess excellent binocular and night vision.

Cat skulls are do.