Over 3,000 dire wolf fossils have been found at the La Brea tar pitsJae C. Hong/AP Photo The La Brea tar pits captured dire wolves, sabertooth cats, and other megafaunal for millennia. Their fossils may show an extinction event 13,000 years ago. Some researchers blame human-set fires for their extinction, but others are skeptical. From about 50,000 years ago, animals, vegetation, and other debris managed to get stuck in the sticky substance of the Rancho La Brea tar pits in present-day Los Angeles.The millions of fossils found in the pits give scientists a time machine into the ancient past and reveal a mysterious mass extinction about 13,000 years ago.