Modern-day Melanesians carry a two-pronged genetic legacy of ancient interbreeding that still affects their health and well-being, researchers say.

Unlike people elsewhere in the world, these Pacific islanders possess nuclear DNA that they inherited from two Stone Age hominid populations, say population geneticist Benjamin Vernot, formerly of the University of Washington in Seattle, and his colleagues. At least some of that ancient DNA contains genes involved in important biological functions, the researchers find. Nuclear DNA is passed from both parents to their children.
The finding means that ancestors of people now living in the Bismarck Archipelago, a group of islands off Papua New Guinea’s northeastern coast, mated with Neandertals as well as with mysterious Neandertal relatives called Denisovans, the scientists conclude online March 17 in Science.

In support of previous research, the researchers find that non-Africans — including Melanesians — have inherited an average of between 1.5 and 4 percent of their DNA from Neandertals. But only Melanesians display substantial Denisovan ancestry, which makes up 1.9 to 3.4 percent of their DNA, the researchers say. (Present-day African populations possess little to no Neandertal or Denisovan DNA.)

The bits of Neandertal and Denisovan DNA carried by Melanesians encompass genes involved in metabolism and immunity, indicating that interbreeding influenced the evolutionary success of ancient humans, Vernot’s group reports.

The new study reconstructs the microscopic landscape of Neandertals’ and Denisovans’ contributions to Melanesians’ DNA “in impressive detail,” says Harvard University paleogeneticist Pontus Skoglund.

Vernot’s team studied DNA from 35 Melanesians at 11 locations in the Bismarck Archipelago. Analyses concentrated on DNA from 27 unrelated individuals. The researchers also looked for evidence of ancient interbreeding in previously acquired genomes of close to 1,500 modern-day individuals from different parts of the world. Denisovan DNA for comparisons came from fragmentary fossils found in a Siberian cave; comparative Neandertal DNA came from a genome previously extracted from a 50,000-year-old woman’s toe bone.
Among Melanesians, DNA sequences attributed to Neandertals and Denisovans encompassed several metabolism genes. One of those genes influences a hormone that increases blood glucose levels. Another affects the chemical breakdown of lipids. Other Melanesian genetic sequences acquired through ancient interbreeding either include or adjoin genes that help to marshal the body’s defenses against illness.

These findings follow evidence suggesting that once-useful genes that ancient humans inherited from Neandertals now raise the risk of contracting certain diseases (SN: 3/5/16, p. 18). Vernot’s group reaches no conclusions about good or bad effects of ancient hybrid genes in Melanesians.

No sign of Neandertal or Denisovan DNA appears in areas of Melanesians’ genomes involved in brain development, the scientists say. So brain genetics, for better or worse, apparently evolved along a purely human path.

Denisovans’ evolutionary history remains poorly understood. Previous DNA comparisons suggest that Denisovans must have reached Southeast Asia. Skoglund suspects that’s where the ancestors of Melanesians bred with Denisovans.

Substantial interbreeding of humans with Denisovans probably occurred only once, Vernot and his colleagues suspect. Genetic exchanges of humans with Neandertals took place at least three times, they add. These estimates are derived from comparisons of shared Denisovan and Neandertal DNA sequences among individuals in different parts of the world.

Bacterium effective when dusted on plants — The successful agent for destroying pesty insects, the microscopic bacterium, Bacillus thuringiensis, is most effective when it is dusted onto tobacco or other plants…. The bacteria are now recommended for use against tobacco budworms and hornworms. From known results …. they look promising as biological control agents. — Science News, April 30, 1966

Update
Bacillus thuringiensis, or Bt, is still used to combat agricultural pests. Different strains of the bacterium target different insects; one strain can even kill mosquito larvae in water. Organic farmers dust or spray Bt on crops and consider it a natural insecticide. In conventional farming, Bt DNA is often inserted into a plant’s genome, creating genetically modified crops that make their own pesticide (SN: 2/6/16, p. 22). In 2015, 81 percent of U.S. corn and 84 percent of U.S. upland cotton contained Bt genes.

Lead contamination in drinking water can change with the seasons. Tracking lead levels in water pipes over several months, researchers discovered three times as much dissolved lead and six times as much undissolved lead in summer than in winter. The finding could help improve water testing, says study coauthor Sheldon Masters, an environmental engineer at Virginia Tech and Corona Environmental Consulting in Philadelphia.

Masters and colleagues analyzed water contamination data collected from pipes in Washington, D.C., and Providence, R.I., and tested the dissolvability of lead in different water conditions. In many, but not all, homes and lab tests, the amount of lead leaching into drinking water rose as water temperature increased.

For pipes in Washington, average wintertime dissolved lead levels were 3.6 parts per billion, compared with 10.8 ppb during summer. Average undissolved lead concentrations varied from 7.6 ppb during winter to 48.4 ppb during summer. Each 1 degree Celsius rise in water temperature boosted dissolved lead levels by about 17 percent and lead particles by about 36 percent, the researchers report online April 14 in Environmental Science & Technology. Washington water temperature varied from about 5° to 30° C. Seasonal variations in lead were smaller than those expected from temperature changes alone, since other factors such as the amount of organic matter in water can also influence lead levels.

Some water systems could meet the regulatory standard of less than 15 ppb in winter while exceeding that threshold during warmer months, the researchers warn. Water testing prioritizes conditions with the highest risk for lead leaching. However, no current guidelines explicitly address seasonal variability. Lead consumption can cause severe health problems including birth defects, anemia and brain damage (SN: 3/19/16, p. 8).

Genetically engineered crops don’t appear to harm humans or the environment, according to a new report released May 17 by the National Academies of Sciences, Engineering and Medicine.

An extensive analysis of two decades’ worth of evidence dug up no substantial proof that genetically engineered foods were any less safe to eat than those that are conventionally bred. The study’s authors also found no conclusive causal link between the engineered crops and environmental problems. The authors note, though, that it’s not always easy to make definitive conclusions; measuring long-term environmental changes is complicated.

The news comes in the midst of political tumult in the United States over laws to label foods made with GE ingredients. But when it comes to food safety and the environment, the authors conclude, how a plant is made isn’t as important as what is actually created.

“It is the product, not the process, that should be regulated,” the authors write.

3-D Home TV Foreseen — The pace of new developments in the recently revived method of photography known as holography is so fast that three-dimensional television sets portraying life-size scenes could be a reality before 1984, as was predicted in George Orwell’s novel…. A hologram is a recording of an interference pattern reflected from an object. From this recording, the object can be reconstructed visually in a three-dimensional form. — Science News, June 11, 1966

UPDATE
Television viewers are still waiting for the 3-D revolution. Although 3-D TVs went on sale in the United States and elsewhere in 2010, they have yet to take off. Most sets require special glasses or have limited viewing angles, and none use holography to create the illusion of depth. Scientists haven’t given up, though. Using innovative plastic screens, researchers are projecting small holographic movies in real time (SN: 12/17/11, p. 18). The enormous bandwidth and processing power needed to transmit and display the images are still huge barriers to making Orwell’s vision a reality.

The biggest ice shelf collapse on record was set in motion years earlier than previously thought, new research reveals.

Analyzing declassified images from spy satellites, researchers discovered that the downhill flow of ice on Antarctica’s Larsen B ice shelf was already accelerating as early as the 1960s and ’70s. By the late 1980s, the average ice velocity at the front of the shelf was around 20 percent faster than in the preceding decades, the researchers report in a paper to be published in Geophysical Research Letters.
Rising temperatures since the 1950s probably quickened the ice flow, which in turn put more strain on the ice and further weakened the shelf, says study coauthor Hongxing Liu, a geographer at the University of Cincinnati. Previous work had suggested that the ice shelf’s downward slide began only a few years before a Rhode Island-sized region of ice disintegrated into thousands of icebergs in 2002.

The new data will help scientists more confidently predict how Antarctic ice will fare in the coming decades, says Penn State glaciologist Richard Alley, who was not involved in the work. The early response of Larsen B to warming “is consistent with this ice shelf system being sensitive, and gives a target for future modeling studies to learn how sensitive, and for what reasons,” he says.

Ice shelves such as Larsen B line Antarctica’s coast and slow the flow of the continent’s glaciers and ice sheets into the sea. Rising temperatures are shrinking Antarctica’s ice, with several ice shelves on track to disappear completely within 100 years (SN Online: 3/26/15). Tracking the long-term decline of ice shelves is tricky, though. Scientific satellite images are sparse prior to the 1990s and next to nonexistent before the 1980s.

Liu and colleagues turned to another group that peered at Antarctica, a U.S. intelligence agency called the National Reconnaissance Office. In 1963, the agency photographed the continent as part of an intelligence-gathering mission. While these images were declassified in 1995, the photos were too distorted by effects such as the camera used and Earth’s curvature to use for ice flow measurements.

Making the photographs usable required identifying stationary landmarks for reference, a difficult task on a continent covered with shifting white ice. Comparing the spy photos with later scientific images, Liu and colleagues identified 44 potential landmarks. Then, using the locations as anchor points, the researchers unwarped the images. Along with additional satellite images snapped in 1979 and the 1980s, the modified images allowed the researchers to track Larsen B’s ice flow over time.
The ice on Larsen B’s front flowed at around 400 meters per year on average between 1963 and 1986, calculations using images from those years indicate. From 1986 to 1988, the average was 490 meters per year. That speed boost suggests that the ice flow accelerated between the 1963 to 1986 satellite images. Several glaciers that feed into Larsen B underwent similar accelerations, the researchers found.

Larsen B’s early acceleration hints that the ice shelf was already weakening well before the 1990s, says Ted Scambos, a polar scientist at the National Snow and Ice Data Center in Boulder, Colo., who was not involved in the study. Previous studies suggested that balmy surface temperatures caused Larsen B’s demise by forming meltwater pools on top of the ice shelf that forced open cracks in the ice (SN: 10/18/14, p. 9). The new satellite data suggest that this fracturing was a finishing blow following long-term weakening by forces such as relatively warm seawater eroding the ice shelf’s underside, Scambos says.

Any parent trying to hustle a school-bound kid out the door in the morning knows that her child’s skull possesses a strange and powerful form of black magic: It can repel parents’ voices. Important messages like “find your shoes” bounce off the impenetrable fortress and drift unheeded to the floor.

But when this perplexing force field is off, it turns out that mothers’ voices actually have profound effects on kids. Children’s brains practically buzz when they hear their moms’ voices, scientists report in the May 31 Proceedings of the National Academy of Sciences. (Fun and not surprising side note: Babies’ voices get into moms’ brains, too.)

The parts of kids’ brains that handle emotions, face recognition and reward were prodded into action by mothers’ voices, brain scans of 24 children ages 7 to 12 revealed. And words were not required to get this big reaction. In the study, children listened to nonsense words said by either their mother or one of two unfamiliar women. Even when the words were fake, mothers’ voices still prompted lots of neural action.

The study was done in older kids, but children are known to tune into their mothers’ voices early. Really early, in fact. One study found that fetuses’ heart rates change when they hear their moms read a story. For a fetus crammed into a dark, muffled cabin, voices may take on outsized importance.

And voices carry particularly powerful messages throughout childhood. “A tremendous amount of emotional information is conveyed to children through auditory channels,” says University of Wisconsin-Madison child psychologist Seth Pollak. And, he points out, kids are small. “Kids’ faces are down around our knees. And children who are crawling are looking at the ground,” he says. This obvious point means that facial expressions and other visual signals might not pack as much punch as a voice.

Of course, voices other than those belonging to moms are also important. Pollak says that voices of fathers — or any other caregiver who spends lots of time around a child — probably affect children’s brains in a similar way. It’s just that those studies haven’t been done yet.

The results of the latest brain scan study make a lot of sense, says Pollak. Some of the brain regions activated are those involved in feeling good. “A caregiver’s voice is actually rewarding. It activates the systems that make us feel calm,” he says.
And the new study might help explain some of Pollak’s earlier results. He and his colleagues stressed out 68 girls, who happened to be the same ages as those in the brain scanning study, by making them do math and word problems in front of three unsmiling adult strangers — a terrifying prospect for most kids. (And adults.) After their ordeal, the girls either talked to their moms in person, on the phone or by instant messenger.

Compared with the instant messenger typers, the girls who saw their moms in person or talked to them on the phone were more soothed, showing lower levels of stress hormones. That finding, published in 2012 in Evolution and Human Behavior, suggests that to a kid, there’s something especially calming about hearing her own mother’s voice.

And now, by showing the widespread reaction to a mother’s voice, the brain data back that up. “It all kind of hangs together in a way that I think is very intuitive,” Pollak says. In other words, a mother’s voice is powerful, perhaps even strong enough to overcome a force field.

Thanks to modern laser technology, Southeast Asia’s Khmer Empire is rising from forest floors for the first time in centuries.

New findings show the remarkable extent to which Khmer people built cities and transformed landscapes from at least the fifth to the 15th century, and perhaps for several hundred years after that, says archaeologist Damian Evans of Cambodia’s Siem Reap Center. Laser mapping in 2015 of about 1,910 square kilometers of largely forested land in northern Cambodia indicates that gridded city streets and extensive canals emerged surprisingly early, by around A.D. 500, Evans reports June 13 in the Journal of Archaeological Science. Researchers have generally assumed that large-scale urban development began later at Greater Angkor, capital of the Khmer Empire from the ninth to 15th centuries (SN: 5/14/16, p. 22).
A helicopter carrying light detection and ranging equipment, lidar for short, flew sorties over seven Khmer sites in the vicinity of Greater Angkor. Lidar’s laser pulses gathered data on the contours of jungle- and vegetation-covered land. Lidar maps revealed city blocks, canals and other remnants of past settlements.
Mysterious ground features previously identified by lidar surveys at Angkor Wat temple in Greater Angkor also turned up at several sites, some located as many as 100 kilometers from Greater Angkor. Those sites include the eighth to ninth century city of Mahendraparvata and a 12th century city, Preah Khan of Kompong Svay. Fields of precisely arranged earthen mounds at these settlements may have been used to collect rainwater, Evans speculates. Earthen embankments forming coiled or spiral patterns might have been gardens or ceremonial spaces.

“It’s humbling to see the lidar data and realize how much was previously missed in ground surveys at Preah Khan,” says archaeologist Mitch Hendrickson of the University of Illinois at Chicago. Hendrickson conducts research at Preah Khan, one of several ancient cities that provided food and other services to Greater Angkor via an extensive road system.

Before the 2015 lidar survey, Mahendraparvata was known “only from inscription texts and a few bits of broken-down masonry,” adds archaeologist Charles Higham of the University of Otago in Dunedin, New Zealand. Mahendraparvata’s laser-traced layout indicates it was an early, small-scale version of Greater Angkor, Higham says.
A military invasion and sacking of Greater Angkor in the 15th century apparently did not result in most of its roughly 750,000 residents abandoning the site, as many investigators have thought. Lidar data from 2015 indicate that Khmer capitals established after Greater Angkor’s defeat, such as Longvek and Oudong, show no signs of dense populations created by mass relocations from the former capital, Evans says.

That suggests that the political state collapsed at Greater Angkor, but hundreds of thousands of rice farmers carried on, Hendrickson says. “Lots of fish and rice were still available,” he says. “Local farmers were more resilient than the state was.”

Coral reefs won’t be out of hot water anytime soon. A global bleaching event that began in June 2014 is the longest on record and now covers a larger area than ever before. What’s worse, it shows no signs of ending.

Global warming exacerbated by the latest El Niño is to blame, National Oceanic and Atmospheric Administration scientists reported Monday at the 13th International Coral Reef Symposium in Honolulu. Since 1979, periodic mass bleachings covering hundreds of kilometers have only lasted for “a year or so,” said NOAA Coral Reef Watch Coordinator Mark Eakin. But this one has dragged on for two years, threatening more than 40 percent of reefs globally, and more than 70 percent in the United States.

When corals are stressed by heat, they reject the colorful algae living inside them and turn a ghostly white. Those algae are a major source of food, so reefs can die if conditions don’t improve.

NOAA scientists aren’t sure what will end this episode. It could extend into 2017, and more frequent events are possible in the future, the scientists said. “Climate models suggest that most coral reefs may be seeing bleaching every other year by mid-century,” Eakin added. “How much worse that gets will depend on how we deal with global warming.”