The early excavations of La Brea simply involved the removal
of bones and the identification of the species present. Since 1969, research
has been more precise and sophisticated. Although few new species are expected
to be recovered, advances in various techniques mean that there is still
a great deal of information to be gained from La Brea.
Fossil plants from La Brea can be particularly informative when determining the climatic conditions at the time of deposition. Many of the fossil plants belong to extant species, so the climate in which these species now live is likely to be similar to that at La Brea in the past.
As the fossil diversity of the La Brea tar pits is so high, it gives a good representation of the ecosystem present in California between 40,000 and 8,000 years ago. However, the fossils give limited information regarding the relative abundance of species, because there is an apparent taphonomic bias towards predator and scavenger species.
The diet of some of the La Brean herbivores can be determined directly from the preservation of pockets of plant material trapped on their teeth. A high proportion of dicotyledons on the teeth of bison, camels and horses supports the pollen and seed evidence suggesting that grasses were probably quite rare at Rancho La Brea.
Geology and Taphonomy
More accurate taphonomic data has allowed a better understanding of the way in which organisms were trapped and preserved.
Although the soft tissue of the La Brea vertebrates is rarely preserved, their hard parts are preserved in detail. Surface features and internal structures such as nasal turbinals and auditory ossicles allow a detailed study of the functional morphology of various species. For example, the hyoid apparatus preserved in some Smilodon specimens indicated that these creatures could purr and roar.
The large number of bones collected means that there are numerous examples of each element to make comparisons with, allowing biometric, ontogenetic and ageing studies to be carried out. For example, an analysis of the dentition of Bison antiquus revealed that juvenile individuals trapped in the tar pits were aged betwee, 2-4 months, 14-16 months or 26-30 months. This indicates that bison were annual migrant visitors to La Brea, since each age group of juveniles is separated by a year.
Around 8,000 of the La Brea specimens show signs of pathology. These may provide information on a variety of subjects. For example, evidence for intraspecific combat in Smilodon has come from the damage observed in their bones. Since the sample size of La Brea is so large, pathology can be used to assess the health of a population. In a recent study by Duckler and Van Valkenburgh, the percentage of pathological specimens in populations of dire wolf, coyote, sabretooth, bison and camel were investigated. When compared to modern healthy and stressed populations, the results indicated that these species did not appear unhealthy in the lead up to their extinctions (except coyote, which is still extant). Information such as this may be important in determining the causes of extinction of these species.
As well as the use of asphalt by Indians centuries ago, La Brea has other links to anthropology. La Brea Woman was a human fossil excavated from the tar pits. She was thought to have dies around 9,000 years ago, at the age of 22-24 years old. Her skull was crushed, suggesting that she had been murdered.
As well as the broad scientific value of La Brea, the tar pits are organised to promote education. The visitor observation centre in Hancock Park allows the public to watch the current excavations from Pit 91, from which arounf 1000 bones a year are recovered. The collections in nearby museums allow a further appreciation of the palaeontological richness of La Brea.
Back to Contents