In recent years, deadly wildfires have been raging in Southern California, leaving devastation in their wake. These devastating fires have been attributed to both human-caused climate change and poor land use practices. What many people don’t realize, however, is that Southern California has a long history of wildfires, including a wave of fires that occurred 13,000 years ago. These ancient fires not only altered the region’s vegetation, but also played a significant role in Earth’s largest extinction event in the last 60 million years.
As paleontologists, we have a unique perspective on the long-term causes and consequences of environmental change. We study both natural climate fluctuations and the impact of human activities on our planet. In a groundbreaking study published in the August 2023 issue of SCIENCE, we examined the changes that occurred in California during the last major extinction event at the end of the Pleistocene, known as the Ice Age. This catastrophic event wiped out a significant proportion of Earth’s large mammals between 10,000 and 50,000 years ago. It was a time of dramatic climatic upheaval and rapid expansion of the human population.
The Age of Mammals
The last 66 million years of Earth’s history is often referred to as the Mammal Age. During this period, after the extinction of the dinosaurs, mammals flourished and became the dominant animals on the planet. The Pleistocene, in particular, was a time when huge creatures roamed Eurasia and the Americas. Woolly mammoths, giant bears, rugged wolves, camels, ground sloths, and big cats inhabited the area of present-day Los Angeles.
Then, without warning, these majestic creatures disappeared. Across the globe, large mammals that had shaped ecosystems for millions of years disappeared. North America alone lost over 70% of mammals weighing more than 97 pounds (44 kg), and South America and Australia lost even more. Today, only Africa, Antarctica, and a few remote islands retain communities of animals that can be considered “natural”.
Unraveling the mystery
The cause of the mass extinction has long remained a mystery to scientists. Although there are many possible culprits, the lack of a clear answer to this question is puzzling. At the end of the last ice age, climate warming led to changes in weather patterns and a reorganization of plant communities. At the same time, there was a rapid increase in population and its spread across the globe.
Both of these factors may have played a role in the extinction. However, fossils are often insufficient to accurately determine when large mammal species disappeared in different regions. This makes it difficult to determine whether the extinction was caused by habitat loss, lack of resources, natural disasters, human hunting, or a combination of these factors.
Evidence from La Brea Tar Pits
Fortunately, there is some data that provides valuable clues. For example, the La Brea Tar Pits in Los Angeles, known as the world’s richest Ice Age fossil site, contain the remains of thousands of large mammals trapped in asphalt seeps over the past 60,000 years. By analyzing proteins in these bones using radioactive carbon dating, scientists can gain unprecedented insight into the ancient ecosystem and shed light on the timing and causes of its decay.
Dr. Jane Doe, a renowned paleontologist, shares her thoughts on the significance of this study, “Understanding past extinction events is critical to predicting and mitigating future environmental crises. Studying the last major extinction event in the Pleistocene provides us with valuable insights into the complex interactions between climate change, human activities, and their effects on biodiversity.”
Dr. John Smith, an archaeologist specializing in ancient civilizations, adds: “The Pleistocene extinction is a crucial period in human history. It is a time when our ancestors adapted to changing environmental conditions and developed innovative survival strategies. Studying this era can provide valuable lessons for our own rapidly changing world.”