Until 11,000 years ago Los Angeles was teeming with wildlife. Though many smaller species still survive, most of the large and exotic mammals became extinct. Explore prehistoric Los Angeles through fossils captured by the La Brea Tar Pits.
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Mastodons from Rancho La Brea tend to be smaller than those found at other localities. They are represented by at least 15 individuals including a baby from Project 23.
The American mastodon was a distant relative of the ancestors of the elephant. During the Pleistocene it ranged from Alaska to Florida. Mastodons differ from mammoths by their smaller size and lower-crowned ridged teeth.
Saber-toothed cats used their 8-inch long canines to help sever the blood vessels of their prey. Isotopic evidence suggests the saber-toothed cats from Rancho La Brea fed mainly on bison and camels.
Saber-toothed cats were powerfully built ambush predators that were only distantly related to true cats. Smilodon fatalis is the California state fossil and remains of more than 2,000 individuals have been recovered from Rancho La Brea.
One of the most distinctive features of modern camels is their hump (dromedary) or humps (bactrian camels) with reserves of fat that enable the camel to go without food for a long time. Camel humps are not supported by skeletal elements so it is impossible to tell whether or not the La Brea camels had humps.
Camels evolved in North America about 45 million years ago and subsequently migrated to Asia, Africa, and South America. The extinct Camelops from Rancho La Brea was as large as living camels but more closely related to living llamas.
Dire wolves were closely related to the living timber wolf but were more stoutly built and had more powerful teeth.
Dire wolves are the most common large mammal from Rancho La Brea and remains of more than 4,000 individuals have been retrieved from the asphalt deposits. Most were probably trapped while attempting to feed on other animals stuck in the asphalt.
Sloths and their close relatives (anteaters and armadillos) are unlike all other mammals in that they have extra articulations in their backbones.
This is the largest and most common of the three species of ground sloth found at Rancho La Brea and may have weighed up to 1,500 lbs. Harlan's ground sloth had small nodules of bone (osteoderms) buried in its skin that provided a kind of armor against attack by predators.
Horses evolved to eat grass but food particles trapped in the teeth of La Brea horses indicate that they were also eating leaves ands shrubs. Unlike the bison, horses were present at La Brea all year round.
Horses evolved in North America about 50 million years ago and survived until about 11,000 years ago. The western horse was one of the last horse species native to North America.
Many of the bison trapped in the asphalt seeps were juveniles. Their age distribution suggests that bison weren't present year-round at Rancho La Brea but migrated through the area during the late spring.
Bison are the most common large herbivores from Rancho La Brea. Originating in Asia, they only entered North America about 200,000 years ago. Their arrival marks the beginning of the Rancholabrean land mammal age.
Coyotes are the third most common large mammal from the asphalt seeps. They are slightly larger than the living coyote but belong to the same species, Canis latrans.
Many of the smaller mammals from the tar pits are still living today though not always in the Los Angeles region. As we know where they live today, we can identify the kinds of habitats present in Los Angeles basin when the asphalt seeps formed.
It is entirely possible that human hunting contributed to the extinction of many large mammals at the end of the Ice Age. However, there is no evidence (yet) of humans living at the same time as dire wolves or mammoths in the Los Angeles region.
Asphalt was used by Native Americans as a glue, to make baskets waterproof, and as a caulk for plank canoes. Marine shells found at the tar pits were brought there by Native Americans as containers for the asphalt.
El Pueblo de Nuestra Señora la Reina de los Ángeles was founded in 1781. The citizens of the pueblo used asphalt from local seeps to waterproof the roofs of their houses and as a fuel.
Before joining the USA, southern California was divided into a number of land grants for use as ranches and farms. One of these land grants, Rancho La Brea (the tar ranch) was named after the asphalt seeps in its southwestern portion.
William Denton, an Englishman who taught at Wellesley College, was given a canine of a saber-toothed cat by the Hancock family when he visited the La Brea Tar Pits in 1875. Denton was the first person to describe fossils from the tar pits.
Fossils from the tar pits were "re-discovered" by oil geologists at the start of the twentieth century. The Hancock family who owned Rancho La Brea had mined the asphalt commercially but abandoned this practice when oil was discovered on their land.
In 1913, the Hancock family gave the newly established Los Angeles County Museum sole right to excavate fossils from the tar pits for two years. Led by L. E. Wyman, excavators earned $3.50 a day, decent wages for 1913.
About a million bones were recovered during the 1913-15 excavations and were housed in the basement of the County Museum. Although about 300 species of animals and plants were recovered, the bones were mainly those of larger animals.
In 1969 the Pit 91 excavation was re-opened with the intent of collecting all the fossils and not just the large vertebrates. As a result the list of species doubled and now over 600 species of plants and animals are known from Rancho La Brea.
The sediment surrounding the larger bones contains microfossils visible only under a magnifier. These include seeds, shells, insect parts, and bones of tiny animals.
In 2006 LACMA built an underground parking garage and encountered 16 new asphaltic fossil deposits. These were recovered in 23 large wooden "tree" boxes - hence "Project 23"- and are currently being excavated by Page Museum paleontologists.
Many exciting fossils are discovered daily in the Project 23 excavations. For details see our blog "The Excavatrix."
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