A Michigan farmer stumbled upon the bones of a woolly mammoth this week.

James Bristle was digging up a soy field near Chelsea, Mich., when an unusual bone caught his attention. At first he thought it was a mere fence post, but closer examination confirmed it was no ordinary find. “We knew it was something that was out of the norm,” Bristle told Michigan Live. “My grandson came over to look at it, he’s 5 years old, he was speechless.”

Dan Fisher, a University of Michigan professor who studies the extinctions of mastodons and mammoths, drove out to the site and confirmed the discovery on Thursday. He said the creature was about 40 years old and was probably killed by humans, who then stashed the remains in a pond as a means of meat storage 10,100 to 15,000 years ago.

The discovery is a major one. Fisher said there are only 10 sites in Michigan where such significant remains of a mammoth skeleton have been uncovered.

[Michigan Live]

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Write to Nolan Feeney at nolan.feeney@time.com.