Health & Science

A touch of the Irish in polar bears

All of today’s polar bears are descended from female brown bears that lived in Ireland during the last ice age. Researchers have come to that startling conclusion by comparing mitochondrial DNA—which reflects only the genetic legacy of mothers—found in modern polar bears with that in bear bones preserved in Irish caves. Though polar bears became a separate species between 2 million and 400,000 years ago, some of them mated with female brown bears as recently as 10,000 years ago, when fluctuating temperatures brought snow-dwelling and forest-living bears into contact with one another. The Irish bear species eventually became extinct, but its hybrid cubs survived and reproduced, and over millennia those offspring proved to be hardier than the offspring of other polar bears. The finding definitely has “implications for polar bears in today’s climate,” study author Ceiridwen Edwards, an archaeologist at Oxford University, tells BBCNews​.com. The modern polar bears’ habitat, Arctic ice, is melting so rapidly that the mammals could soon become critically endangered, and grizzlies are moving north into Arctic territory. That’s already resulted in polar-grizzly couplings—and a few “prizzly” cubs. Scientists now think such hybrids deserve special protection, because they “may play an underappreciated role in the survival” of the polar bear.

Why cancer is riskier for men

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Men are much more likely than women to die of almost every type of cancer, a new report by the National Cancer Institute shows, and those poorer odds may be largely reversible. Males have higher mortality rates not because they’re worse at fighting off cancer, but because they are more likely to develop it in the first place. Researchers examined the effects of 36 cancers on both sexes in a database containing 30 years’ worth of statistics. They found that men were five times more likely to die from lip and throat cancers, and three times more likely to die from urinary and bladder cancers. More than twice as many men as women die from lung cancer, which kills more people than any other form. These cancers “are all related to lifestyle,” Mikkael Sekeres, a researcher at the Cleveland Clinic, tells Health.com. Smoking—a habit more common among males than among females—almost certainly plays a significant role. But it’s also a question of just seeing the doctor in time. Women tend to receive earlier diagnoses, which makes their cancers more treatable. By contrast, a recent study shows that almost a third of men fail to visit a doctor regularly.

Sequencing the spud

The humble potato has a complex genetic code, but researchers say they’ve finally cracked it and created a genome map that could help breed healthier, more nutritious spuds. The tubers are notoriously vulnerable to blights like the one that caused the Irish potato famine in the 1840s. Knowing how their genes work should allow scientists to create “potatoes that are more resistant to disease, require less water to grow, and contain more vitamins and other nutrients,” study author Jeanne Jacobs, a researcher at the New Zealand Institute for Plant & Food Research, tells ABC Science. She and colleagues from 14 countries had to figure out which potato genes control which traits and chart their location within the spuds’ chromosomes, a particularly difficult task since potato cells have four often very different copies of every chromosome—twice as many as human cells have. But by using new DNA-sequencing tools, the researchers were able to identify the function of more than 39,000 genes. At least 800 are meant to fight disease, they discovered, but many of those have been damaged or destroyed, possibly by decades of inbreeding. Now that scientists know where they are, however, they can work on activating them to shore up potato defenses.

Dinosaurs’ sudden demise

A fossil of the last known dinosaur to walk the earth may help answer long-standing questions about why the prehistoric beasts disappeared, the London Guardian reports. Many scientists believe that dinosaurs were wiped out in a single blow when a giant asteroid crashed into the planet near Mexico’s Yucatán Peninsula some 65 million years ago. Others have argued that the massive reptiles were already extinct by then, having died off gradually because of climate change or increased volcanic activity. But the new fossil, likely the horn of a triceratops, was discovered in Montana a mere 5 inches below a layer of sediment that marks the time when the asteroid landed. That means the animal was probably “doing very well right up until” that cataclysmic event, says study author Tyler Lyson, a paleontologist at Yale University. “It indicates that the impact was the likely cause of the extinction.” Previously, no dinosaur fossils had appeared closer than 10 feet from the meteor layer. Now, Lyson argues, the only question is not whether the collision destroyed the creatures but how. “I’m confident,” he says, that “we will find more dinosaurs within this interval” that can help explain what happened. It will just take more digging.