Fossilized teeth of Ice Age predators yield clues to why certain species survived

Paleontologist Larisa DeSantis studies ancient predators trapped in the La Brea Tar Pits. Courtesy Vanderbilt University.

Visitors to the La Brea Tar Pits in Los Angeles are accustomed to seeing recreated scenes of, say, extinct saber-tooth cats taking down a horse or bison in an open field. But according to the most detailed study yet of Ice Age predators by paleontologists at Vanderbilt University, this would have been an extremely rare occurrence. They describe a different ecological scenario in their latest paper in Current Biology—one in which saber-toothed cats preferred to hunt under the cover of a forest, while dire wolves preferred to track their prey in open environments. And their findings may offer valuable hints about why some ancient predator species went extinct (dire wolves and saber-toothed cats), while others survived (coyotes).

The so-called Pleistocene Epoch dates from 2.5 million years ago to roughly 10,000 years ago, a time period that includes dramatic shifts in climate and the evolution of humans into the ecological mix. The La Brea Tar Pits is one of the best repositories for preserving the remains of now-extinct ancient species from this era. For tens of thousands of years, animals would become mired in the tar, gradually getting sucked down into the pit before dying of asphyxiation.  Over time, their remains became fossilized as the lighter fractions of the petroleum evaporated, leaving the bones trapped in a more solid substance until archaeologists uncovered them thousands of years later. And there are far more carnivore and predator specimens in the pit than herbivores, perhaps because they were drawn to the pits when herbivores became mired in the tar, and became mired themselves.

The first recorded sighting of the La Brea Tar Pits is in 1769, when the Spanish governor of Baja California headed an excursion down what is now Wilshire Boulevard in midtown Los Angeles. The expedition observed large marshes of a pitch-like substance, bubbling and boiling.  The George C. Page Museum of La Brea Discoveries now stands adjacent to the pits, where scientists continue to excavate new fossilized remains from the tar to this day, aided by volunteers during the summer keen to hunt for fossilized treasure.

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