Rancho La Brea is the location of famous tar pits, or asphalt pits as they're more properly known, where pre-historical animals became trapped and preserved between 10,000 and 40,000 years ago, near the end of the last Ice Age.
The area with it deadly black tar pits, disguised as watering holes, became known as the "Miracle Mile", though we might know it better as a section of Wilshire Boulevard, just east of Beverly Hills, California.
Today the sticky asphalt still oozes to the surface through natural fissures in the rocks. No longer do saber-tooth tigers, dire wolves or mammoths come to drink the water covering the sticky pools. Today there are only sparrows, pigeons and rabbits.
Europeans first took note of this site on August 3, 1769, when Gaspar de Portola wrote, "For three hours we proceeded on a good road; to the right of it were extensive swamps of bitumen which is called chapa-pote. We debated whether this substance, which flows melted from underneath the earth, could occasion earthquakes."
For thousands of years these swamps of asphalt have been fed by springs of oil, and in the slightly moister climate of the last Ice Age they were covered with water which lured thirsty animals to their doom. Coming to drink in the area, they went to the pools, where a misstep entangled them in sticky asphalt. Their struggles and cries attracted predators and scavengers which, in turn, became entangled in the asphalt, adding more bait to the trap.
Near the end of the last Ice Age, the Los Angeles basin looked very much as it did when the first Europeans came to California. The rainfall averaged only a few inches more a year, the native trees crept a little further down the hillsides and out onto the plain to form a savanna; and the sky was hazy, not with smog but with fog and haze trapped by the temperature inversion that often holds eye-burning smog in the basin today.
The wildlife, however, was completely different. The only way to picture North America in the geologic past is to think in terms of African game. The species were different, but the herds of herbivores and packs of stalking carnivores looked much the same.
In any animal community the herbivores, eaters of grass and leaves, make up the bulk of population. Since a carnivore such as a mountain lion requires one deer every week or ten days for food, obviously there must be many more deer than mountain lions. This economy normally prevailed in the geological past, but among the millions of bones recovered from the La Brea tar pits the ratio is reversed.
There, carnivorous mammals outnumber the herbivores ten to one; and among birds, 75 percent are hawks, eagles, falcons, condors or vultures. Vast numbers of carnivorous animals were attracted to the asphalt pools by the sight of an easy meal and, in turn, became trapped themselves. So saber-tooth tigers, dire wolves and coyotes are the most common fossils in the pits.
There are no dinosaur remains. Dinosaurs became extinct nearly 70 million years before the first drop of sticky oil bubbled to the surface at Rancho La Brea.
Certainly the most spectacular mammals at Rancho La Brea were mammoths and slightly smaller mastodons. Arriving across the Bering Strait land bridge from Asia some two million years ago, mammoths quickly spread throughout the continent and diversified into many species.
The largest mammal to roam southern California was the imperial mammoth, which sometimes stood 13 feet high at the shoulder. The scarcity of mammoths in the tar pits may be due to their greater strength, higher intelligence or smaller numbers.
Mastodons and their near relatives were earlier immigrants to the New World, entering about 15 to 20 million years earlier. They were smaller than mammoths, with elongated heads and, occasionally, small tusks on lower jaws.
To those familiar with American and African wild animals, ground sloths seem the most bizarre creatures of the time. Standing slightly over four feet high, when walking on all fours, these massive, bulky animals made their way into North America from South America when the two continents were rejoined after 60 million years of isolation. The strange construction of the sloths' feet and limbs gave them their unusual gait. Their ancestors were South American tree sloths which had become adapted for hanging upside down from branches. When some were forced out of forests and onto the plains, they re-adapted for ground living, but their twisted feet did not become straightened again. Instead, they retained the "curl" developed by their ancestors. Thus the ground sloth walked on the knuckles of his front feet and the outer sides of his back feet. This stance caused modification of the limb bones, which made them unique among mammals. There were three kinds of sloths in the Rancho La Brea area, but some paleontologists believe this was not their normal habitat. Perhaps the ones trapped in the asphalt were passers-by who just stopped for a drink.
The only other unusual herbivore in the area was the camel, which had a body about like that of the modern camel, but with somewhat longer legs. It is not generally known, but the camel is a native of North America and a fairly recent emigrant into Eurasia. The earliest member of the family dates back 40 million years.
The other large herbivores are familiar to all of us- horses, bison and deer. The bison was somewhat larger than the modern species, and there were a few giants whose horns had a span of nearly twelve feet.
Many of the carnivores are old friends of the modern forest and plain: foxes, badgers, skunks, weasels, mountain lions, lynx, black bears and grizzly bears. These have changed little, and if we had their entire carcasses to study we might find they differed from their modern counterparts only at the subspecies level.
The carnivore that seems strangest to us is the saber-tooth tiger. The largest known assemblage of saber-tooth cat fossils comes from Rancho La Brea. Through the years, they must have flocked in vast numbers to feed on animals trapped in the asphalt. Paleontologists don't agree whether saber-tooths made their living by hunting active prey. In the Rancho La Brea area they hunted the weak, the young, the dying, the sick and the old. Their relatively weak hind legs, their massive forelegs, and their great sabers were well suited for dispatching the weak and cutting up carrion.
All the saber-tooth cats were well adapted for their way of life, and their design was frozen almost as soon as they appeared. It is said imitation is the sincerest form of flattery, and in the case of saber-tooth cats, it must be so.
Several times during the age of mammals, lineages of true cats adapted to this mode of life and became "false saber-tooths." In South America, where all mammalian carnivores were once marsupials (animals which carry their young in pouches), there was a marsupial saber-tooth that nearly out-sabered Northern Hemisphere types. The saber-tooth, perhaps, symbolizes Rancho La Brea to most people, not only because of its numbers, but because of its exotic form and its (perhaps unwarranted) reputation as a mighty hunter.
Outnumbering saber-tooths were Dire Wolves. Packs of them roamed southern California by the thousands. Slightly smaller than the northern timber wolf, the Dire Wolf ranged through North America for thousands of years. Fossils have been found as far east as Kentucky and as far south as Mexico City. Leg proportions indicate it was not as swift a runner as the modern timber wolf, and thousands of individuals in the asphalt pits suggest the great packs were scavengers when given the chance. The common coyote also ranged the Los Angeles basin and frequented Rancho La Brea. Only minor differences separate it at the sub-specific level from the living species, the familiar singer of the American West.
Two carnivores stand out among the fossils recovered from the tar pits because of their size, although few individuals are known. The Great Cat structurally resembled the jaguar, although the males were nearly a quarter larger than the biggest living cats. Ranging North America during the closing days of the last Ice Age, this magnificent species was certainly the mightiest hunter of its day.
Exceeding the Great Cat in size was the Short-Faced Bear. On all four feet it stood a foot higher than the modern Grizzly Bear, and was more massively built than the Kodiak Bear. Its teeth suggest a more carnivorous way of life than any living bears.
With two exceptions, the birds of Rancho La Brea would seem familiar to all but the most highly trained observer. Many of the species or their close relatives are still living nearby today. The two exceptions are the La Brea stork, unknown in California today, and the huge condor-like vulture, teratorn.Teratorns include some of the largest known flying birds, having wingspans of 12 feet or more. The number of these scavengers found in the pits makes one think at times the sky was clouded with circling teratorns.
Today, the center of Rancho La Brea is a county park, named for the donor of 23 acres, Captain G. Allan Hancock, a descendant of the original California family that uncovered the first La Brea fossils during asphalt mining operations in 1875.