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 10,000 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 R.O.V. pilot at the institute. Not everyone believed him at first, but Mr. Prickett was able to convince 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 scimitar-shaped 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 Dr. 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, Dr. 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 Dr. 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 Dr. 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. The sun was barely cresting the horizon on the morning of July 29 when the boat finally reached its target. Dr. Haddock and his team wasted no time getting their search underway, stationing themselves in the ship’s control room while the rest of the crew was still eating breakfast.
An air of excitement filled the dark room as the scientists watched on screens while the R.O.V., 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 some 10,000 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 R.O.V. 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,” Dr. Haddock said.
The crew was delighted, but they couldn’t celebrate just yet. They still had to collect the tusk, and there was no guarantee it would go smoothly. Dr. Haddock and his team were concerned that the long tooth might be too fragile to pick up, so they took their time recording photos and videos that could be used to create a 3-D model in case it broke during their recovery attempt.
Household sponges and soft plastic fingers had been attached to the arms of the vehicle to make it easier for the pilots to gently pick up the tusk. The room fell silent as the grippers reached for the encrusted fossil. Everyone in the room watched nervously as the robot lifted the tusk. Then, ever so gently, the drone moved the object into its collection drawer. The second the tusk was released, the silence was broken by a torrent of applause. The tusk had been found and recovered in just under two hours.
A short while later, the R.O.V. returned to the surface and was brought back onboard the ship. Dr. Haddock and Dr. Fisher moved the tusk to the ship’s lab and wasted no time measuring, cleaning and photographing the specimen.
After donning a pair of gloves and some sterile coveralls, Dr. Moon joined in. She pulled out a wire saw and sliced a chunk of the tusk off, allowing her to sample its innermost tissue. She said she hoped this sample contained more mammoth DNA than was recovered from the sampling of the tusk’s tip two years ago — enough to determine the species of mammoth that ended up in this watery grave, as well as its lineage.
“We’re all incredibly excited,” Dr. Moon said. “This is an ‘Indiana Jones’ mixed with ‘Jurassic Park’ moment.”
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,” Dr. Moon said that day on the ship. Recent advances in the field of ancient DNA have allowed genetic studies of animals up to one million years old.
After Dr. Moon collected her samples, the tusk was handed off to Dr. 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 three feet long, was covered in a thick iron-manganese 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, Dr. 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 and are not definitive.
“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,” Mr. Mol added, and studying one could give scientists new insights about the Lower Paleolithic, a poorly understood era of Earth’s history.
Scientists know that around 200,000 years ago Earth was experiencing a glacial period and our ancestors were migrating out of Africa. But they don’t know exactly how the planet’s changing climate affected mammoths and other large animals during this time. What is also unclear is how arrival to North America altered the genetic diversity of mammoths.
“We don’t really know much of anything about what was happening during that time period,” Dr. Fisher said. “We don’t have access to a lot of specimens from this time period and that’s due in large part to the fact that getting access to sediments of this age is difficult.”
Mammoths, the furry, small-eared relatives of modern elephants, first appeared around five million years ago and became extinct around 4,000 years ago. The first mammoths came out of Africa and spread north, evolving into distinct species along the way, until they had colonized much of the Northern Hemisphere.
The earliest mammoths to venture into North America were known as Krestovka or steppe mammoths. These mammoths came from Eurasia 1.5 million years ago and did so by marching across the Bering Strait, which wasn’t covered by water like it is today. Hundreds of thousands of years later, another species of mammoth, the woolly mammoth, also crossed the Bering Strait and joined their cousins in North America. The two hybridized to produce the Columbian mammoth, but no one knows exactly when. A recent study estimated that the hybridization event occurred at least 420,000 years ago, but more research is needed to confirm this.
If the tusk is as old as scientists suspect, it “could really help clarify the timing of this hybridization event,” said Pete Heintzman, an associate professor at the Arctic University Museum of Norway who studies the DNA of mammoths and other ice age creatures.
Although exposure to saltwater can be destructive to biological tissue, the deep sea can be ideal for DNA preservation.
“It’s dark, cold and environmentally stable,” said Dr. Heintzman, who is not involved with the ongoing analysis of the tusk. The best-preserved remains typically come from permafrost and caves, which like the deep sea have low, stable temperatures and no light.
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 Mr. Mol, who has helped discover the remains of numerous mammoths in the shallow waters of the North Sea. He recommended that deep-sea explorers “start bringing paleontologists with them when they explore the seafloor because they know what to look for.”
Dr. 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,” Dr. 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 Dr. 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-a-lifetime experience for me to have this encounter with this creature,” Dr. 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.”
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