A series of catastrophic fires 13,000 years ago led to the extinction of many large mammals in southern California, according to a new study of fossils from the La Brea tar pits. The research suggests that these devastating fires were likely caused by a combination of human activity and a changing ecosystem. By killing off herbivores and deliberately starting fires, humans unintentionally created conditions that fueled the fires and ultimately led to the collapse of the ecosystem. The study, conducted by Robin O’Keefe at Marshall University in West Virginia, highlights the potential for human activities to have far-reaching consequences on the environment.
The La Brea tar pits in Los Angeles have long been a rich source of fossils, providing valuable insights into the past. However, many of these fossils have never been precisely dated due to the challenges posed by radiocarbon dating. Now, with advances in technology, O’Keefe and his colleagues were able to date 172 bones from eight different species, shedding new light on the timeline of extinction events in the area. The study revealed that seven species, including the sabre-toothed cat, dire wolf, and ancient bison, disappeared from the La Brea area around 13,000 years ago, coinciding with a significant increase in wildfires. These findings have important implications for understanding the impact of human activities on ecosystems and the potential for future extinctions.
Catastrophic fires led to extinction of large mammals in southern California 13,000 years ago
A new study of fossils from the La Brea tar pits in southern California has revealed that a series of catastrophic fires were the immediate cause of the extinction of many large mammals in the region 13,000 years ago. The research suggests that these extreme fires were likely a result of humans abruptly changing the ecosystem by killing off herbivores and deliberately starting fires. The combination of a drying climate, the removal of herbivores, and the increase in vegetation created a feedback loop that ultimately led to a chaotic state in the ecosystem. The fires were described as catastrophic, with some fire events producing significantly more charcoal particles than ever before.
Dating the fossils
The La Brea tar pits have trapped and preserved numerous animal bones over the past 50,000 years, providing a unique glimpse into the past. However, many of these bones had never been precisely dated due to the cost and destructive nature of previous radiocarbon dating methods. Now, advances in technology have made it possible to date tiny quantities of bone without destroying the entire specimen. By using preserved collagen from the bones, researchers were able to precisely date 172 bones from eight species, seven of which are now extinct.
Shift in vegetation and impact on fire
Pollen in lake sediments revealed that the vegetation in the La Brea area began changing from woodland to a more open landscape around 16,000 years ago, as the region became drier due to the retreat of ice sheets. However, there was a sudden shift to fire-resistant vegetation around 13,000 years ago, coinciding with the disappearance of the large mammal species. The study suggests that humans played a role in increasing fire activity both directly through ignitions and indirectly through hunting herbivores. The findings highlight the potential for ecosystems to flip into another state and result in the extinction of many species.
Implications for current wildfires and conservation
The research has significant implications for understanding the impact of wildfires in the present day. As global temperatures rise, extreme wildfires are becoming more frequent in many parts of the world. The study suggests that these fires have the potential to push ecosystems into a chaotic state, leading to the extinction of multiple species. The lead researcher, Robin O’Keefe, emphasizes the relevance of these findings to current times, urging society to learn from the past and change our trajectory to prevent further damage to ecosystems and species.
Takeaways
The study of fossils from the La Brea tar pits in southern California has revealed that catastrophic fires, likely caused by humans, led to the extinction of large mammals in the region 13,000 years ago. The combination of a drying climate, the removal of herbivores, and deliberate fire-starting created a feedback loop that resulted in a chaotic state in the ecosystem. The research highlights the potential for current wildfires to have a similar impact on ecosystems, leading to the extinction of multiple species. The findings call for urgent action to prevent further damage to ecosystems and species in the face of climate change.
