One of the most extraordinary aspects of the fossil deposits at Rancho La Brea is the preservation of not just a few fossils, but instead an entire prehistoric ecosystem. From the smallest plant fragments to the largest mammals, the fossilized remains of Rancho La Brea number well into the millions. The evidence is complete enough that scientists can reconstruct the environment that existed in Los Angeles 12-40,000 years ago.

Fossils from Rancho La Brea can be organized into categories according to what they ate, how they produced food and how they relate to each other. These nutrient categories are "trophic levels" in a food pyramid or "links" in a food chain. There are producers (green plants that manufacture their own food through photosynthesis); herbivores (plant eaters); carnivores (meat eaters) and scavengers and decomposers that reduce and recycle organic remains at all trophic levels.

		Foot Note! With so many species (nearly 650) represented and so many specimens (nearly 3.5 million), the collection contains large populations of plants and animals, not merely a small sample. For example, excavations have discovered thousands of sabertoothed cats, representing every age group and gender. By looking at this population and comparing the younger cats to the older ones, scientists can tell how their teeth grew and how their bones grew and fused. By looking at their healed injuries and bone infections, scientists can even start to see how they may have lived and behaved!

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