An Ice Age paleontological-turned-archaeological site in San Diego preserves 130,000-year-old bones and teeth of a mastodon that show evidence of modification by early humans. Analysis of these finds dramatically revises the timeline for when humans first reached the Americas, according to a paper authored, in part, by Museum paleontology staff and published in the April 27 issue of the prestigious science journal Nature.
The fossil remains were discovered by Museum paleontologists in 1992 during routine paleontological mitigation work at a freeway expansion project site managed by the California Department of Transportation (Caltrans). The bones, tusks, and molars, many of which are sharply broken, were found deeply buried alongside large stones that appeared to have been used as hammers and anvils, making this the oldest in situ, well-documented archaeological site in the Americas.
Until recently, the oldest records of human sites in North America generally accepted by archaeologists were about 15,000 years old. But the fossils from the Cerutti Mastodon site (as the site is being referred to in recognition of the Museum’s very own field paleontologist Richard Cerutti who discovered the site and led the excavation), were found embedded in fine-grained sediments that had been deposited much earlier, during a period long before humans were thought to have arrived on the continent.
Since its initial discovery, this site has been the subject of research by top scientists to accurately date the fossils and evaluate microscopic damage on bones and rocks that authors now consider indicative of human activity. In 2014, state-of-the-art radiometric dating methods were used to determine that the mastodon bones—which were still fresh when they were broken by strategically-placed blows from hammerstones—were approximately 130,000 years old.
The finding poses a lot more questions than answers: Who were these people? Are they part of an early—but failed—colonization attempt? Or is there a long, but as of yet, scarcely recognized presence of humans in this hemisphere?
Asking questions is at the heart of scientific discovery–uncovering new information and always seeking the best explanation that fits the evidence, no matter what we thought was true before. Fossils tell stories. This is not the end of this story, but simply the beginning.
Recovery of the fossils was supported by Caltrans District 11. Funding for research was provided by the National Geographic Society, as well as the Walton Family Fund, Pat Boyce and Debbie Fritsch, and the James Hervey Johnson Charitable Educational Trust.
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