A new study published in the journal Quaternary Research has significantly revised the age of South Dakota's Mammoth Site, pushing its estimated timeline back by more than 100,000 years. The site, discovered in 1974 during a housing project, contains the remains of over 60 young male Columbian mammoths, the highest concentration of such fossils in North America. Previously, scientists believed the site dated to about 26,000 years ago, placing it in the later part of the Pleistocene epoch. However, new findings suggest the mammoths lived more than 160,000 years ago, placing them in a much earlier period of this era, known for its ice ages and megafauna. The Mammoth Site was found when workers uncovered massive tusks while digging for a new home. Researchers Jim Mead, an emeritus scientist at the Mammoth Site and the University of Arizona, and Larry Agenbroad, a former professor at Northern Arizona University and the site’s former director, began excavating the area. They discovered that the site was a sinkhole formed when the ground above collapsed, likely due to groundwater dissolving the underlying rock. This created a deep, deadly pit—between 13 to 16 feet—where the air was warm, around 90 to 95 degrees Fahrenheit, and the steep, slick walls made escape impossible for the mammoths. Other prehistoric animals, including a short-faced bear, North American camel, wolf, and coyote, were also trapped in the pit. Dating the remains was complicated by the lack of collagen, a protein commonly used in radiocarbon dating. Instead, researchers used bone apatite, a mineral in the bones, but the results were inconsistent. Some dates ranged between 23,000 and 42,000 years, while others suggested ages of 129,000, 150,000, and 101,000 years. To resolve the confusion, scientists turned to luminescence dating, which measures how long mineral grains in the surrounding sand have been buried and shielded from sunlight. While quartz grains were not helpful, feldspar samples provided consistent results, suggesting the site is between 160,000 and 232,000 years old. Emma Krolczyk, a geologist with the U.S. Geological Survey, explained that carbon in the bones can mix with carbon from surrounding groundwater, potentially skewing radiocarbon dating results. One sample from the middle of the sinkhole was about 40,000 years younger than surrounding samples, which may be due to a variety of geological factors. Paul Hanson of the University of Nebraska-Lincoln emphasized the need to consider variations in dating methods across different sites. Researchers are now exploring other techniques, such as uranium-thorium dating, to confirm these findings. Accurate dating is essential for understanding the environment and evolution of large mammals in the Black Hills. While much of the site has been excavated, the bottom third remains untouched, and scientists believe more mammoths or other extinct species may still be buried there, though storage space is currently a limiting factor in further exploration.