Ancient Fires Drove Large Mammals Extinct, Study Suggests

Subject: Science and technology

Section: Msc

About the new Study:

In a new study a group of paleontologists that analyzed fossil records at La Brea Tar Pits, a famous excavation site in Southern California, concluded that the disappearance of sabertooth cats, dire wolves and other large mammals in this region nearly 13,000 years ago was linked to rising temperatures and increased fire activity spurred by people.

Research findings:

The team analyzed fossils for eight large mammal species — including the sabertooth cat, the American lion and Camelops hesternus, an ancient camel — that lived between 10,000 and 15,600 years ago.
- Using radiocarbon dating, the team determined that seven of these species went extinct around 13,000 years ago.
To figure out why, the researchers analyzed climate, pollen and fire records in the region alongside continental human population growth at the time.
- They found that human occupation began to rise rapidly around the same time that Southern California entered a period of severe drought and warming.
- Extreme fires ensued, and the vegetation, once rich in juniper and oak trees, was eventually replaced by grass and chaparral shrubs.
The scientists determined that humans were the primary drivers of these fires, both through direct ignition and by the elimination of herbivores, which allowed flammable underbrush to spread uncontained.
Shifts in the climate exacerbated this further, setting the stage for the extinction of species.
This pattern could not account for the notable disappearance of large mammals elsewhere in the world at the end of the last ice age.

Similarities with the present day climate trends:

Climate records during the ice age extinction indicate a warming of about 10 degrees Fahrenheit over 1,000 years.
Today, temperatures in Southern California have risen about 5.4 degrees Fahrenheit in only the past century.
Increased fire activity after the arrival of humans has also been documented in other locations, including Australia, Hawaii and Canada and India.

La Brea Tar Pits, California, USA:

La Brea Tar Pits is one of the few sites in the world with a large enough fossil record for scientists to investigate the mass extinctions.
The pits, which are still active across 13 acres of land, are filled with bubbling black asphalt that has seeped to the surface from inside Earth.
Prehistoric animals that became stuck in this goo died of fatigue or predation, and the asphalt fossilized and preserved their remains. And that’s still happening today.
La Brea now boasts a continuous fossil record of the region stretching as far back as 55,000 years.

Mass extinction on earth:

Earth has seen five mass extinction events so far; some scientists argue that the disappearance of large mammals at the end of the last ice age was the start of a sixth.
It was the biggest extinction event since an asteroid slammed into Earth and wiped out all the dinosaurs.