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Honymand via Wikimedia Commons // CC BY-SA 4.0
Honymand via Wikimedia Commons // CC BY-SA 4.0

Some Woolly Mammoths Survived Until Just 5600 Years Ago

Honymand via Wikimedia Commons // CC BY-SA 4.0
Honymand via Wikimedia Commons // CC BY-SA 4.0

Quick: Name all the Ice Age animals you can think of. There’s the woolly mammoth, and the … woolly mammoth … and the … yeah. You’re not wrong; woolly mammoths did live in the Pleistocene, or Ice Age. But they may have made it further into the present day than we thought; new evidence suggests the big beasts were tromping around in our own Holocene Age as recently as 5600 years ago. The results were published in the Proceedings of the National Academy of Sciences

Today, the volcanic region of St. Paul Island is fairly isolated, lying about 200 miles south of mainland Alaska. But thousands of years ago it was part of the mainland itself, forming one tiny section of the Bering Land Bridge. The bridge played a huge role in the history of our planet, allowing humans and countless other species—including mammoths (Mammuthus primigenius)—to spread across the Northern Hemisphere. 

St. Paul Island today. Image credit: Bill Briggs via Wikimedia Commons // CC BY-SA 3.0

But the bridge was not to last. Temperatures rose on Earth. Glaciers began to melt. Sea levels began to rise. Gradually, animals migrated to the highest ground they could find. Over time, those areas of high ground—like the top of the St. Paul volcano—became islands. 

The first mammoth remains were found on St. Paul Island in 1999. Radiocarbon dating the bones of the five animals revealed that they were surprisingly recent, about 6500 years old. That’s long after mammoths had disappeared from the mainland. There was no evidence of human life, and scientists wondered what it was that finally took the mammoths out

To find out, they checked in with the mammoths and their island. Researchers drilled down into a lakebed at the center of the island and extracted three samples of compressed sediment, each slightly deeper than the last. Those samples were combined into a long, composite core, packed with information about the world that was. 

From that master sample, the team scooped out smaller samples. Some were examined for evidence of microscopic coprophilous—that’s poop-eating—fungi. Finding, quantifying, and identifying that fungi could help determine how well the mammoths (the fungi’s preferred food source) were doing. 

Next, they sequenced the core’s sedimentary DNA, which allowed them to identify tiny traces of life. Then they scanned the sample for signs of other life, including microscopic crustaceans, algae, plants, and pollen. Finally, they found and analyzed the remains of an additional 14 mammoth specimens. 

The results of this ecosystem-wide approach were kind of grim. Radiocarbon dating of the newly discovered mammoths found that the beasts had lived about a thousand years closer to the present day than had previously been believed, but the world they inhabited was a rough one. 

The island, it seems, had begun to dry out around about 7800 years ago. Levels of nitrogen and carbon isotopes increased in the mammoths’ plant diet, suggesting the plants—and thus the mammoths—were getting thirsty. The island began to die. Then, about 5600 years ago, signs of mammoth and other life dropped precipitously. 

Aptly named co-author Matthew Wooller is director of the Alaska Stable Isotope Facility at the University of Alaska Fairbanks. “It paints a dire picture of the situation for these mammoths,” he said in a press statement. “Freshwater resources look like the smoking gun for what pushed them into this untenable situation.” 

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Ted Cranford
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science
Scientists Use a CT Scanner to Give Whales a Hearing Test
Ted Cranford
Ted Cranford

It's hard to study how whales hear. You can't just give the largest animals in the world a standard hearing test. But it's important to know, because noise pollution is a huge problem underwater. Loud sounds generated by human activity like shipping and drilling now permeate the ocean, subjecting animals like whales and dolphins to an unnatural din that interferes with their ability to sense and communicate.

New research presented at the 2018 Experimental Biology meeting in San Diego, California suggests that the answer lies in a CT scanner designed to image rockets. Scientists in San Diego recently used a CT scanner to scan an entire minke whale, allowing them to model how it and other whales hear.

Many whales rely on their hearing more than any other sense. Whales use sonar to detect the environment around them. Sound travels fast underwater and can carry across long distances, and it allows whales to sense both predators and potential prey over the vast territories these animals inhabit. It’s key to communicating with other whales, too.

A CT scan of two halves of a dead whale
Ted Cranford, San Diego State University

Human technology, meanwhile, has made the ocean a noisy place. The propellers and engines of commercial ships create chronic, low-frequency noise that’s within the hearing range of many marine species, including baleen whales like the minke. The oil and gas industry is a major contributor, not only because of offshore drilling, but due to seismic testing for potential drilling sites, which involves blasting air at the ocean floor and measuring the (loud) sound that comes back. Military sonar operations can also have a profound impact; so much so that several years ago, environmental groups filed lawsuits against the U.S. Navy over its sonar testing off the coasts of California and Hawaii. (The environmentalists won, but the new rules may not be much better.)

Using the CT scans and computer modeling, San Diego State University biologist Ted Cranford predicted the ranges of audible sounds for the fin whale and the minke. To do so, he and his team scanned the body of an 11-foot-long minke whale calf (euthanized after being stranded on a Maryland beach in 2012 and preserved) with a CT scanner built to detect flaws in solid-fuel rocket engines. Cranford and his colleague Peter Krysl had previously used the same technique to scan the heads of a Cuvier’s beaked whale and a sperm whale to generate computer simulations of their auditory systems [PDF].

To save time scanning the minke calf, Cranford and the team ended up cutting the whale in half and scanning both parts. Then they digitally reconstructed it for the purposes of the model.

The scans, which assessed tissue density and elasticity, helped them visualize how sound waves vibrate through the skull and soft tissue of a whale’s head. According to models created with that data, minke whales’ hearing is sensitive to a larger range of sound frequencies than previously thought. The whales are sensitive to higher frequencies beyond those of each other’s vocalizations, leading the researchers to believe that they may be trying to hear the higher-frequency sounds of orcas, one of their main predators. (Toothed whales and dolphins communicate at higher frequencies than baleen whales do.)

Knowing the exact frequencies whales can hear is an important part of figuring out just how much human-created noise pollution affects them. By some estimates, according to Cranford, the low-frequency noise underwater created by human activity has doubled every 10 years for the past half-century. "Understanding how various marine vertebrates receive and process low-frequency sound is crucial for assessing the potential impacts" of that noise, he said in a press statement.

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Scientific Reports, Fernando Ramirez Rozzi
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Stones, Bones, and Wrecks
Humans Might Have Practiced Brain Surgery on Cows 5000 Years Ago
Scientific Reports, Fernando Ramirez Rozzi
Scientific Reports, Fernando Ramirez Rozzi

In the 1970s, archaeologists discovered a site in France containing hundreds of cow skeletons dating back 5000 to 5400 years. The sheer number wasn't surprising—human agriculture in that part of the world was booming by 3000 BCE. What perplexed scientists was something uncovered there a few decades later: a cow skull bearing a thoughtfully drilled hole. Now, a team of researchers has released evidence that suggests the hole is an early example of animal brain surgery.

Fernando Ramírez Rozzi, a paleontologist with the French National Center for Scientific Research, and Alain Froment, an anthropologist at the Museum of Mankind in Paris, published their findings in the journal Nature Scientific Reports. After comparing the opening to the holes chiseled into the skulls of humans from the same era, they found the bones bore some striking similarities. They didn't show any signs of fracturing from blunt force trauma; rather, the hole in the cow skull, like those in the human skulls, seemed to have been carved out carefully using a tool made for exactly that purpose. That suggests that the hole is evidence of the earliest known veterinary surgery performed by humans.

Trepanation, or the practice of boring holes into human skulls, is one of the oldest forms of surgery. Experts are still unsure why ancient humans did this, but the level of care that went into the procedures suggests that the surgery was likely used to treat sick patients while they were still alive. Why a person would perform this same surgery on a cow, however, is harder to explain.

The authors present a few theories, the first being that these ancient brain surgeons were treating a sick cow the same way they might treat a sick human. If a cow was suffering from a neural disease like epilepsy, perhaps they though that cutting a hole in its head would relieve whatever was agitating the brain. The cow would have needed to be pretty special to warrant such an effort when there were hundreds of healthy cows living on the same plot of land, as evidenced by the skeletons it was found with.

Another possible explanation was that whoever operated on the cow did so as practice to prepare them for drilling into the heads of live humans one day. "Cranial surgery requires great manual dexterity and a complete knowledge of the anatomy of the brain and vessel distribution," the authors write in the study. "It is possible that the mastery of techniques in cranial surgery shown in the Mesolithic and Neolithic periods was acquired through experimentation on animals."

Either way, the bovine patient didn't live to see the results of the procedure: The bone around the hole hadn't healed at all, which suggests the cow either died during surgery or wasn't alive to begin with.

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