NEWS AND NOTES ABOUT SCIENCE
THE FINAL HOURS OF THE ICEMAN’S TOOLS
In 1991, scientists in the Italian Alps came across a frozen, caramel-colored corpse face down in the melting ice. They named him Ötzi, or the Iceman. And since that time, researchers have been learning more and more about the Iceman’s life in the Copper Age in Europe some 5,300 years ago.
The latest findings, published recently in the journal PLOS One, are focused on the tools he carried with him. A small dagger, a couple of arrowheads and a few other prehistoric possessions made of stone, wood and deer antler, provide insight into their owner’s mysterious final days before he was shot with an arrow and died.
Dr. Ursula Wierer, an archaeologist from the provincial Department of Archaeology, Fine Arts and Landscape in Florence, Italy, used high-power microscopes and a CT scanner to examine Ötzi’s dagger and arrowheads. Other items in his ancient tool kit included a small, sharp flake for cutting reeds; an oval-shaped stone called an end-scraper; a jagged-looking rock used for making holes in leather and wood called a borer; and a wooden block with a deer’s antler called a retoucher.
“He cared about his tools,” said Wierer, adding that many showed signs of being resharpened or repaired.
All of the items had been recovered in the glacier gully near Ötzi’s body. They included a quiver containing just two arrowheads and a dozen unfinished arrow shafts, several antler points and a bundle of sinew, or animal tendons. Ötzi must have been in some sort of rush, said Wierer, as he did not have the time to construct a working bow or complete his other dozen arrowheads before his death.
Ötzi’s dagger was unusually small with a blade that was barely a couple of inches long. Its tip was also broken, so it lacked a sharp point. The blade was made of a hard, dark rock called chert that is similar to flint. To sharpen it, Ötzi would have had to apply pressure and flake off its edges, rather than scrape it against another rock.
The chert that Otzi used was mined from three different areas, which were as far as 40 miles away, Wierer said. And in his final moments, the Iceman ran out of chert to fix his tools. Nicholas St. Fleur
MAGNETIC SENSE HELPS BILLIONS OF MOTHS ON AN AUSTRALIAN MIGRATION
Every spring in Australia, billions of bogong moths migrate from the arid plains of Queensland, New South Wales and Victoria to the meadows of the Australian Alps to escape the impending heat. There, they congregate in caves like living shingles, and go dormant over the summer. Autumn arrives, and they return to their birthplaces to mate, lay eggs and die. The eggs hatch into caterpillars that develop underground through winter. The cycle continues.
How these animals complete this epic journey to a place they have never been and back, traveling hundreds of miles at night, for days to weeks each way, has long been a mystery. But scientists have now discovered that bogong moths have a magnetic sense to help them.
In a paper published recently in Current Biology, they tested how the moths reacted to moving visual cues and magnetic fields in an outdoor flight simulator and found that the winged insects use magnetic fields like a compass. While other animals like nocturnal songbirds and sea turtles are known to migrate by Earth’s magnetic fields, the researchers say this is the first reliable evidence that insects can, too.
Australia’s small, brown, ordinary-looking bogong moths are the only known insect besides the monarch butterfly to manage such a long, directed and specific migration.
“They have this sort of amazing ability that belies their appearance,” said Eric Warrant, a biologist at the University of Lund in Sweden and the principal investigator of the study. “It’s as if the bogong moth is the drearycolored, nocturnal cousin of the monarch butterfly.”
But unlike the monarch, the moth flies at night beneath dim constellations and a darting, shape-shifting moon.
“Originally, I thought the moth would mostly be using celestial cues,” Warrant said. The dung beetle, for instance, follows polarized light, the moon or the Milky Way to roll a ball of excrement along a perfectly straight path. But it sustains this path for just a few minutes. By contrast, the moths stay directed all night. Joanna Klein
SECRETS OF SURVIVORS OF A SEA STAR PLAGUE
In the summer of 2013, the ocher sea stars of the California coast fell victim to a deadly plague.
First they developed ominous white patches. Then, their rotting arms began to detach from their bodies and crawl away. They did not make it far.
“They just kind of dissolve within days,” said Lauren Schie-
belhut, a biologist at the University of California, Merced, who studies the creatures.
More than 80 percent of the ocher sea stars on the northern coast died as a result of that outbreak of sea star wasting syndrome, as the disease is called. In the wake of the devastation, Schiebelhut and her colleagues looked at the survivors and wondered: Did they have something that the dead did not?
In a new paper in the Proceedings of the National Academy of Sciences, they report a detectable difference between the genes of sea stars before the epidemic and the survivors. Genetic tests also show that new generations of sea stars have more in common with the survivors than with past generations — the events of 2013 seem to have left an indelible mark on the sea star’s gene pool.
The ocher sea star makes its home in rocky tide pools all along the California coast. Before the outbreak, the researchers had taken tissue samples at 16 different locations. Afterward, they took samples from the survivors in the same locations. Using several kinds of genetic testing, they found that some sequences were more common in sea stars now than they had been before, while others were less common.
Then, they turned their attention to the juvenile sea stars that appeared after the outbreak.
The researchers thought that when the next batch of young sea stars appeared, they would resemble previous generations.
But that was not the case. By the time the researchers surveyed the new sea stars, the ones still living were more similar to the survivors. The scientists believe that those descended from the dying sea stars grew ill and died upon their return to the tide pools.
They saw the same shift in multiple locations, suggesting that it was not random. Rather, it is more likely we are seeing natural selection happen before our eyes. There was something about the sea stars that made it through that allowed them, and not their neighbors, to survive. Veronique Greenwood
A CLAM THAT USES ACID TO MAKE ITS HOME
When a burrowing giant clam is very young, only about half a millimeter long, it picks out the home it will have for the rest of its life. It attaches itself to the rock of a reef, and as time passes, it grows larger. Simultaneously, it sinks into the rock at an imperceptibly slow rate.
When a scuba diver swims by an adult clam on one of the Pacific reefs where they live, all she will see is what looks like a protruding pair of beautiful turquoise lips. These are the clam’s feeding tissues, basking in the sun and filtering food from the water — the rest of its body is safely encased in a cave of its own making.
How exactly a clam could do that has long been a mystery. But in a new study in Biology Letters, researchers revealed at long last a probable tool: The clam’s foot releases acid.
That’s illuminating because reefs are built by tiny coral organisms that create their own skeletons out of calcium carbonate. When they die, they leave behind their hard shells, and their descendants make their homes in and on the resulting hummocks. Mix calcium carbonate and acid, however, and the molecules of the rock dissolve, in the same reaction you would see if you dropped an Alka-Seltzer into Coca-Cola, which is weakly acidic.
Decades ago, researchers had suspected that the clams used acid, as well as perhaps sanding down the stone using their rough shells. But when they released pH-sensitive fluid into the seawater around clams, there was no change.
Richard Hill, a biologist at Michigan State University who is an author on the new paper, and his co-authors wondered whether looking for acid in the seawater wasn’t the wrong way to go about it — the acid might only be found on the flat surface where the foot was pressing.
Soon, the team had nine burrowing giant clams resting comfortably on flat, color-changing pH-sensitive foil in lab tanks. When they used a camera to photograph the foil from the bottom, the evidence was clear: The shape of the clams’ feet was visible in light red, indicating that they had created an acidic environment at least two pH levels stronger than that of the seawater. Further testing showed that the feet contained a molecular pump that moves around hydrogen ions, or protons, to make acid. Veronique Greenwood
EXTINCT GIBBON FOUND IN CHINESE TOMB
British researchers have identified a gibbon found in an ancient Chinese tomb as a never-before seen, now-extinct genus and species.
Samuel Turvey, a conservationist and gibbon expert, was touring a Chinese museum in 2009 when a partial skull caught his eye. It had been found buried, along with several other animals in the tomb of Lady Xia, a grandmother of China’s first emperor Qin Shihuang, in what is now Shaanxi, China. The tomb was estimated to be 2,200-2,300 years old.
Turvey was struck by the shape of the head, which did not look like any modern animal he knew, said James Hansford, a postdoctoral student in Turvey’s lab at the Institute of Zoology, Zoological Society of London.
A new paper, published in Science, confirms that his instinct was correct. Turvey’s research team identified the animal as a member of a new genus and species, Junzi imperialis. Gibbons were seen as a symbol of scholar officials in ancient China, and junzi means “scholarly gentlemen.”
There are four gibbon genera alive in Asia today, including a species that is the most endangered mammal on earth.
In comparison to living gibbons, the new one has a comparatively flat, small face, Hansford said, with canines that are particularly long for the animal’s size.
The team was not able to do DNA analysis on the cranium and jaw, but, using digital scans, compared its shape to skulls from hundreds of animals across Asia and in collections in Germany and England, Hansford said. “This one sticks out as really different, something definitely separate as a genus,” he said.
No other gibbon has ever been found in a tomb, said Susan Cheyne, who was not involved in the research, but who collaborates with team members. It is extremely rare, she said, to find such old gibbon remains anywhere because their forest habitat tends to degrade bones quickly.
The animal’s placement in the tomb suggests it was kept as a pet. Such a practice could have been devastating to the species, and may explain why it went extinct, said Cheyne, an associate lecturer in primate conservation at Oxford Brookes University.