La Brea Tar Pits

At Rancho La Brea in the middle of Los Angeles, natural asphalt has seeped from the ground for tens of thousands of years. Pools of sticky tar, often hidden under water or leaves, trapped animals that stepped in them. The first fossils there were found in the 1870s, and large excavations began in the early 1900s. Most of the deposit dates from about 50,000 to 11,000 years ago. It has produced millions of bones, from over 600 species of plants and animals, including mammoths, mastodons, giant ground sloths, bison, horses, camels, dire wolves and Smilodon.¹²

About 90 percent of the large animals found are carnivores or scavengers, which is unusual. The best explanation is that predators coming to feed on a trapped herbivore became stuck themselves, and the calls of a struggling animal drew in more. Dire wolves are the most common large mammal, with the remains of thousands of individuals. Because the asphalt preserves bone and even plant remains and insects, the site also shows what vegetation and climate were like. Scientists can use the long series of bones and teeth to study changes in diet, disease and body size through the end of the Ice Age. The La Brea Tar Pits are still being excavated today, with a museum next to the site.¹²