Scientists have used fossil specimens found at the La Brea Tar Pits in Southern California to assess how climate change affected the evolution of Ice Age predators.

Saber-toothed cats and dire wolves, the larger and more ferocious relatives of modern wolves, died out at the end of the last Ice Age, but through studying the links between climate change and these Ice Age predators, scientists hope to predict how animals will respond to climate change today.

At the end of the last Ice Age, about 11,000 years ago, climate was unstable, with periods of rapid warming and cooling that had an impact on the evolution of life.

A research team from the Page Museum at the La Brea Tar Pits analyzed fossils from dire wolves and saber-toothed cats and found significant changes over time in the shapes and properties of the ancient animals' skulls.

"When we compare fossils deposited at different times, we see big changes. We can actually watch evolution happening," said Robin O'Keefe, lead author on the dire wolf study recently published in the journal Palaeontologia Electronica.

As the last Ice Age was coming to an end, marked by glaciers receding and climate warming, the La Brea dire wolves became smaller and more graceful, the researchers report.

A similar evolution occurred in saber-toothed cats, according to Julie Meachen of Des Moines University, who lead the research on sabertooth cats, published in the Journal of Evolutionary Biology.

"Saber-toothed cats show a clear correlation between climate and shape. Cats living after the end of the Ice Age are larger, and adapted to taking larger prey," Meachen said.

Both Meachen and O'Keefe are research associates at the Page Museum.

"We can see animals adapting to a warming climate at La Brea," said O'Keefe. "Then humans show up and all the big ones disappear. We haven't been able to establish causality there yet. But we are working on it."

In the video below, the researchers describe their work.