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Why was this ancient tusk 150 miles from land?

Question draws mix of researchers to search 3,000 feet deep in the Pacific

By Annie Roth

© The New York Times Co.

A young female mammoth was wandering long ago near what would become the Central Coast of California, when her life came to an untimely end. Although she died on land, her massive body found its way into the Pacific Ocean. Carried by currents, her remains drifted more than 150 miles from shore before settling 3,000 feet beneath the water’s surface on the side of a seamount. There she sat for millenniums, her existence known to no one.

However, that all changed in 2019 when scientists from the Monterey Bay Aquarium Research Institute stumbled upon one of her tusks while using remotely operated vehicles to search for new deep-sea species off the coast of Monterey, Calif.

“We were just flying along and I look down and see it and go ‘that’s a tusk,’ ” said Randy Prickett, a senior ROV pilot at the institute. Not everyone believed him at first, but Prickett was able to persuade his colleagues to go in for a closer look. “I said ‘if we don’t grab this right now you’ll regret it.’ ” The crew attempted to collect the mysterious object. To their dismay, the tip of the scimitarshaped specimen broke off. They picked up the small piece and left the rest behind.

It wasn’t until the scientists examined the fragment that they were sure that what they had stumbled upon was indeed a tusk. But from what animal and what time period was still unknown.

The discovery of such a specimen in the deep sea is unusual. Tusks and other skeletal remains of prehistoric creatures are usually found deep underground or encased in permafrost near the Arctic Circle. Although some specimens have been found in shallow waters in Western Europe’s North Sea, the remains of a mammoth, or any ancient mammal for that matter, have never been found in waters so deep.

Steven H.D. Haddock, a marine biologist at the institute who led the 2019 survey, usually focuses on bioluminescence and the ecology of gelatinous deep-sea organisms. But he couldn’t resist the allure of this scientific stumper. So he put together a team of scientists from the institute, the University of California, Santa Cruz and the University of Michigan to solve the mystery.

Preliminary research by Haddock’s colleagues presented the possibility that this wasn’t just any mammoth — instead, it might have been one that died during the Lower Paleolithic, an era that lasted 2.7 million through 200,000 years ago and from which well-preserved specimens are sparse.

Further study of this specimen may help answer long-held questions about the evolution of mammoths in North America. The discovery also suggests that the ocean floor could be covered in paleontological treasures that will add to our knowledge of the deep past. But before the team could really advance the science, they’d have to head back out to sea to collect the rest of the tusk.

On July 27, I boarded the Western Flyer, MBARI’s largest research vessel, with an assortment of other crew. Along for the ride were Daniel Fisher, a paleontologist at the University of Michigan who studies mammoths and mastodons, and Katherine Louise Moon, a postdoctoral researcher at the University of California, Santa Cruz who studies the DNA of ancient animals.

Before the outing, Moon was able to extract just enough DNA from the broken tip to determine that the tusk came from a female mammoth. Her conclusion was supported by Fisher, who said the tusk’s shape and size were characteristic of a young female mammoth. Terrence Blackburn, another researcher at Santa Cruz, was unable to join the trip, but his preliminary work also provided an estimate of how many years it had been since the mammoth died.

Back on the boat, it took two days to reach the undersea mountain where the tusk was as Haddock and his colleagues stopped at various points along the way to collect rare and undescribed species of jellyfish and ctenophores, invertebrates also known as comb jellies.

An air of excitement filled the dark room as the scientists watched on screens while the ROV, named the Doc Ricketts after the famous marine biologist who influenced John Steinbeck, slowly descended into the depths. By the time the aquatic drone had reached its destination, the side of a seamount 3,060 feet deep, the room was packed with scientists, engineers and members of the ship’s crew, all eager to witness the rediscovery of the tusk.

Almost everything on the sloping seamount below the ROV was covered in a black iron-manganese crust. That at first made spotting the tusk difficult. However, after less than 15 minutes of searching, the quarry suddenly appeared on one of the screens.

“It’s exactly how we left it,” Haddock said.

Extracting and analyzing the DNA of ancient animals like this mammoth “is fairly routine for us now, which is a really cool thing to say,” Moon said that day on the ship. Recent advances in the field of ancient DNA have allowed genetic studies of animals up to 1 million years old.

After Moon collected her samples, the tusk was handed off to Fisher for analysis to reveal the mammoth’s age when it died, and what conditions were like during its lifetime. As of November, neither researcher had completed their studies, but their initial results seem promising.

The tusk, which was roughly 3 feet long, was covered in a thick ironmanganese crust. The deep sea is rich in these metals, and in some places an iron-manganese shell will form around any object that stays in one place long enough — at least a few thousand years. The thickness of the crust suggested the tusk was old, but to find out exactly how old, Blackburn, whose lab at Santa Cruz specializes in geochronology, studied the decay of radioactive materials in samples of the original tusk tip retrieved in 2019.

He estimated that the tusk had been sitting on the seafloor for much more than 100,000 years, although these findings have yet to be peer-reviewed.

“It’s a treasure,” said Dick Mol, a paleontologist with the Historyland museum in the Netherlands, who was not involved with the recovery or analysis of the tusk.

Mammoth tusks that are over 100,000 years old are “extremely rare,” Mol added, and studying one could give scientists new insights about the Lower Paleolithic, a poorly understood era of Earth’s history.

Regardless of how much DNA scientists are able to extract from this tusk, there is much that can be learned by studying its tissue. Elephants, mammoths and other proboscideans store vast quantities of information in their tusks. They grow layer by layer, creating a structure that resembles a stack of ice cream cones.

Like the rings of trees, the size and shape of these layers can tell scientists a great deal about the life history of the animal with near-daily resolution, including, in the case of females, how often they produced offspring. Additionally, each microscopic layer contains isotopes that reflect what the animal was eating. These isotopes can be traced back to specific locations, allowing scientists to learn not only what the animal was eating, but where.

Whatever the scientists manage to learn from this mammoth tusk, it is unlikely to be the only preserved remains of an ancient land animal in the ocean.

“There are probably a lot more out there,” said Mol, who has helped discover the remains of numerous mammoths in the shallow waters of the North Sea.

Haddock takes another lesson from the discovery: the deep sea needs protection from mining and drilling. “In this really unique, underexplored and largely underappreciated environment, there is a lot of value in having habitat that is undisturbed,” Haddock said.

The tusk was surrounded by polymetallic nodules, naturally forming clusters of minerals found only in the deep sea that are rich in valuable elements such as manganese, iron, nickel, titanium and cobalt. Although no one has started harvesting the nodules, mining companies have not been quiet about their desire to do so.

Had the seamount where Haddock and his team found the specimen been disturbed by the extraction of oil or minerals, it is likely that the tusk would have been buried by sediment, and never found. The deep sea is Earth’s largest habitat and the vast majority of it is unprotected. Preserving this vast and mysterious realm could not only ensure a future for the countless creatures that live there, the scientists say, but it could also ensure that natural, ancient treasures can still be found.

“It’s been a once-in-alifetime experience for me to have this encounter with this creature,” Haddock said. “I keep imagining what life was like for this mammoth. I think about how its tusk ended up in the ocean and how it was just waiting for us to come across it for so long.”

Tagged in: deep ocean deep sea

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