Oceans are some of Earth's most biodiverse places. They’re home to animals so weird that people have seriously suggested them as proof of alien life, animals so small they can’t be seen without a microscope – and now, apparently, remains of animals so large their name is a synonym for “big.”
We’re not talking about blue whales – they’re amazing, but hardly a surprising find in the ocean. What marine biologist Steven Haddock and ROV pilot Randy Prickett found at the bottom of the Pacific Ocean in 2019 was much weirder: a mammoth tusk.
“In the deep sea, we find lots of amazing animals which people would not believe exist on Earth,” Haddock told Gizmodo. “But finding this mammoth tusk, so deep and so far from shore, was by far the most improbable thing I’ve experienced.”
“As it dawned on us that this was actually a mammoth, my head began to spin imagining how it came to rest atop this remote seamount,” added Haddock. “It is still hard for me to believe how it sat there for millennia without being destroyed or buried before we stumbled across it.”
The tusk was found while exploring a seamount – an underwater mountain formed by volcanic activity – during an expedition with the Monterey Bay Aquarium Research Institute (MBARI). The tusk was about 300 kilometers (185 miles) off the coast of California, and over three kilometers (10,000 feet) deep underwater.
The bottom of the Pacific isn’t very hospitable: it averages around 3.5 degrees Celsius (38 degrees Fahrenheit) and is subject to more than 100 MPa (nearly 15,000 psi) of pressure. However, it’s precisely those conditions that allowed the tusk to survive as long as it did.
“This specimen’s deep-sea preservational environment is different from almost anything we have seen elsewhere,” University of Michigan paleontologist Daniel Fisher, who specializes in the study of mammoths and mastodons, said in a statement about the discovery. “Other mammoths have been retrieved from the ocean, but generally not from depths of more than a few tens of meters.”
Initially, Haddock and Prickett could only collect a small piece of the tusk – it took over a year before they could go back and retrieve the whole thing in July 2021. Once ashore, the researchers at MBARI confirmed that the tusk came from a Columbian mammoth (Mammuthus columbi), a gigantic beast that once populated what is now almost the entire US and most of Mexico.
Other than the species, there’s a lot that’s not yet known about the tusk. The team isn’t even sure exactly how old the specimen is – though preliminary tests put it at way more than 100,000 years old. If that’s true, it would be the oldest well-preserved tusk recovered from the region.
“Our age estimate on the tusk is largely based on the natural radioactive decay of certain uranium and thorium isotopes imparted to the tusk from the ocean,” explained Terrence Blackburn, associate professor of Earth and planetary sciences and head of the UCSC Geochronology Lab. “If the tusk had been found on land, deciphering its history would not be as straightforward.”
Now that the tusk has been fully recovered, the team plans to examine its internal structure using CT imaging. Hopefully, this will also help pin down the age of the find. Meanwhile, oceanographers will be studying the ocean currents to try to figure out exactly how the tusk ended up where it did (Columbian mammoths were likely pretty good swimmers, but even so, 185 miles is pushing it).
If all goes as planned, researchers from USCS’s Paleogenomics Lab think this lone tusk may change what we know about how mammoths got to the Americas. They plan to use the incredibly preserved specimen to sequence the mammoth’s DNA. By comparing it to DNA from other mammoth remains, they hope to reveal never-before-seen insights into the ancient animal.
“Specimens like this present a rare opportunity to paint a picture both of an animal that used to be alive and of the environment in which it lived,” said Beth Shapiro, who leads the USCS team. “Mammoth remains from continental North America are particularly rare, and so we expect that DNA from this tusk will go far to refine what we know about mammoths in this part of the world.”