Localities of the Pleistocene:
When this photograph was taken around 1910, the location depicted was describedas "the Salt Creek oilfields, 7 miles west of Los Angeles." Today, thisspot is in the middle of downtown Los Angeles, eloquent testimony to urbansprawl, but thepoolsand deposits of asphalt still remain. For these are the La Brea tar pits,containing one of the richest, best preserved, and best studied assemblagesof Pleistocenevertebrates,including at least 59 species ofmammal andover 135 species ofbird.The tar pit fossils bear eloquent witnessto life in southern California from 40,000 to 8,000 years ago; aside fromvertebrates, they includeplants, mollusks, andinsects -- over660 species of organisms in all.
Tar pits form when crude oil seeps to the surface through fissures in theEarth's crust; the light fraction of the oil evaporates, leaving behind theheavy tar, or asphalt, in sticky pools. Tar from the La Brea tar pits wasused for thousands of years by local native Americans, as a glue and aswaterproof caulking for baskets and canoes. After the arrival of Westerners,the tar from these pits was mined and used for roofing by the inhabitantsof the nearby town of Pueblo de Nuestra Señora la Reina de LosAngeles.
The bones occasionally found in the tar were first thought to be those ofunlucky cattle. It was not until 1901 that the first scientific excavationof the pits were carried out. Scientists from the University of Californiaat Berkeley, notably ProfessorJohn C. Merriam andhis students, were among the first researchers to work on the La Brea fossils.Today, the George C. Page Museumof La Brea Discoveries, right next door to the tar pits themselves,displays huge numbers of La Brea fossils. The Page Museum is part of theNatural History Museum of Los AngelesCounty.
Life in Los Angeles was somewhat cooler and moister 40,000 years ago thanit is today, as we can tell by examining the plant fossils from La Brea.Many of the plants and animals found in La Brea are identical or almostidentical with species that still live in the area -- or that would beliving in the area had Los Angeles not gotten in the way. Yet a number ofthe large animal species found at La Brea are no longer found in NorthAmerica: native horses, camels, mammoths and mastodons, longhorned bison, andsabre-toothed cats.
In today's ecosystems herbivores are much more abundantthan carnivores. It is therefore curious thatat La Brea about 90% of the mammal fossils found representcarnivores. Most of the bird fossils are also predators or scavengers,including vultures, condors, eagles, and giant, extinct, storklike birdsknown as teratorns.Why is this the case? If a pack of carnivorous mammals were to chase a loneprey animal into the tar pits, both predators and prey would become trapped.This would not have to be a frequent occurrence -- an average of onemajor entrapment every ten years, over a period of 30,000 years,would be sufficient to account for the number of fossils found at La Brea.Scavenging animals, drawn to feed on trapped animals, would have achance of getting trapped themselves. This would explain the preponderanceof carnivores and scavengers.
A few denizens of the La Brea tar pits, now in theUniversity of CaliforniaMuseum of Paleontology collections, aredepicted below. Click on any picture to receive an enlarged version.
 | Smilodon californicus Smilodon, the most famous of the sabre-toothed cats,is the second most common fossil at La Brea. Literally hundreds of thousandsof its bones have been found, representing thousands of individuals.It was first described by Professor John C. Merriam andhis student Chester Stock in 1932. Today, it is the California statefossil. But Smilodon was not restricted to California; it rangedover much of North and South America. For more about how this fearsome beast lived,you can visit our special virtual exhibition,Sabretooths!. |
 | Canis lupus furlongi This fossil was originally described as the species Canis milleri, butrestudy has shown that it is a subspecies of C. lupus, the gray wolf.In the Pleistocene, gray wolves shared the region with C. dirus, thedire wolf. Gray wolves had the largest natural range of any mammal speciesexcept for hom*o sapiens; at one time they were found in every habitatof the Northern Hemisphere except for deserts and the tropics. Today, thegray wolf has largely been exterminated in Europe, the UnitedStates except for Alaska, and Mexico. |
For more about La Brea, visit the George C. Page Museum, located by the pits themselves.
The artist William Gordon Huff from Berkeley sculpted severalof the animals from La Brea for the Museum of Paleontology's exhibit atthe Golden Gate International Exposition of 1939 and 1940. You canview a virtual exhibit onHuff's sculptures for yet another perspective on life at La Brea.
Harris, J. M. and Jefferson, G.T. (eds.) 1985. Rancho La Brea:Treasures of the Tar Pits. Natural History Museum of Los Angeles County.
