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The fossils of 180 insects may indicate that the climate of southern California has been stable for the last 50,000 years.

Researchers have found that the fossils preserved in the La Brea Tar Pits—which form one of the world’s richest Ice Age fossil sites—include seven species of beetles that offer a glimpse of the environment for southern California throughout history.

“Despite La Brea's significance as one of North America's premier Late Pleistocene fossil localities, there remain large gaps in our understanding of its ecological history,” lead author Anna Holden, a graduate student at the American Museum of Natural History's Richard Gilder Graduate School and a research associate at the La Brea Tar Pits and Museum, said in a statement.

“Recent advances are now allowing us to reconstruct the region's paleoenvironment by analyzing a vast and previously under-studied collection from the tar pits: insects,” she added.

Insects are able to adapt to highly specific environmental conditions, making them ideal candidates to offer clues to the environments of the past. Most insects are capable of migrating when they or their habitats get too hot, too cold, too wet or too dry.

The researchers found fossils for ground beetles and darkling beetles, which are still native to the area, clueing in the research team that the climate has not changed much over the course of time. These beetles are restricted well-known habitats and climate ranges.

The researchers used radiocarbon dating and estimated that the beetle fossils could be grouped into 28,000 to 50,000 years old, 7,500 to 16,000 years old and 4,000 years old. The researchers found that the beetles stayed in the area for a sustained period of time, meaning the insects were content with the environmental conditions.

“With the exception of the peak of the last glaciers during the late Ice Age about 24,000 years ago, our data show that these highly responsive and mobile beetles were staples in Los Angeles for at least the last 50,000 years, suggesting that the climate in the area has been surprisingly similar,” Holden said. “We hope that insects will be used as climate proxies for future studies, in combination with other methods, to give us a complete picture of the paleoenvironment of Earth.”

The study was published in Quaternary Science Reviews.  

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