Bones once believed to belong to a woolly mammoth and thought they could rewrite the timeline of mammoth extinction have turned out to come from a completely different and unexpected animal.
The fossilised remains, consisting of two epiphyseal plates from a large mammal’s spine, were discovered in 1951 by archaeologist Otto Geist during an expedition in Alaska’s interior, just north of Fairbanks. The region, known as Beringia, is famous for yielding fossils of Ice Age megafauna, including mammoths, bison and ancient horses.
Given the size of the bones and their location, Geist’s identification of them as woolly mammoth remains seemed reasonable. Late Pleistocene mammoth fossils are common in the region, and the vertebrae were large enough to fit an elephant-sized animal. Geist sent the specimens to the University of Alaska Museum of the North, where they remained in storage for more than seven decades.
Only recently were the fossils re-examined, thanks to the museum’s ‘Adopt-a-Mammoth’ programme, which helped fund radiocarbon dating. The results were startling. The bones were dated to just 2,000 to 3,000 years old far too young to belong to a woolly mammoth.
Mammoths are believed to have disappeared from mainland North America around 13,000 years ago, with a few isolated populations surviving on remote islands until about 4,000 years ago. If the Alaskan bones truly belonged to a mammoth, they would have represented the youngest mammoth remains ever found.
“Mammoth fossils dating to the Late Holocene from interior Alaska would have been an astounding finding,” wrote University of Alaska Fairbanks biogeochemist Matthew Wooller and his colleagues in a peer-reviewed study. “If accurate, these results would be several thousand years younger than the latest evidence for mammoth in eastern Beringia.”
Before rewriting the history of mammoth extinction, the researchers took a closer look at what the bones actually were.
The radiocarbon dates raised the first red flags, but chemical analysis provided stronger clues. The bones contained unusually high levels of nitrogen-15 and carbon-13 isotopes. While these isotopes can occur in land animals, they are far more common in marine food webs and tend to accumulate in ocean-dwelling species.
No mammoth from eastern Beringia has ever shown such an isotopic signature, which makes sense given that the interior of Alaska is hundreds of kilometres from the sea.
“This was our first indication that the specimens were likely from a marine environment,” the researchers explained.
Physical appearance alone could not solve the mystery. Experts agreed that the bones were too fragmentary and weathered to confidently identify by shape. The team turned to ancient DNA analysis, hoping genetics would reveal the true species.
Although nuclear DNA could not be recovered due to degradation, researchers managed to extract mitochondrial DNA. When compared with known genetic sequences, the results showed that the bones did not belong to a mammoth at all. Instead, they matched whale species, including the North Pacific right whale and the common minke whale.
With that discovery, the mystery shifted rather than disappeared.
“How did the remains of two whales that are more than 1,000 years old end up in interior Alaska, more than 400 kilometres from the nearest coastline?” the researchers asked.
The team explored several possibilities. One idea was that whales may have swum inland through ancient river systems or inlets, though this seems highly unlikely given the size of these animals and the limited food available in inland waters. While rare cases of “wayward” whales have been recorded elsewhere, none are known from Alaska’s interior.
Another possibility is human transport. Ancient coastal communities in other parts of the world have been known to move whale bones inland for tools, construction or ritual purposes. However, there is no clear evidence of such practices in interior Alaska.
The final explanation is a potential mix-up in museum records. Otto Geist collected specimens from many parts of Alaska and donated them over several years. The bones may have been mislabeled or misplaced during archiving in the early 1950s.
The researchers acknowledge that the question may never be fully answered. What is clear, however, is that the bones do not belong to the last surviving mammoths.
“Ultimately, this effort has successfully ruled these specimens out as contenders for the youngest mammoths,” the team concluded.
The study was published in the Journal of Quaternary Science, serving as a reminder that even long-held assumptions in museum collections can still hold surprises and that science often advances by questioning what we think we already know.