Some ants are so good at navigating they can do it backward.

Researchers think that foraging ants memorize scenes in front of them to find their way back to the nest. But that strategy only works when facing forward. Still, some species have been observed trekking in reverse to drag dinner home.

To find out how the ants manage this feat, Antoine Wystrach of the University of Edinburgh and colleagues captured foraging desert ants (Cataglyphis velox) near a nest outside Seville, Spain. In a series of tests, the researchers gave the ants cookie crumbles and then released the ants at a fork in the route back to their nest.

Regardless of which direction they took, ants walking backward with cookie bits in tow maintained a straight path. The researchers suspect the ants relied on some sort of sunlight cues. Ants also appeared to peek behind themselves to check and adjust course. After making adjustments, ants maintained their new direction no matter their body orientation. Desert ants combine their celestial compass and long-term visual memories of the route to find their way home, the team concludes online January 19 in Current Biology.

Blobs of gas near the Milky Way’s center may be just the right mass to harbor young stars and possibly planets, too. Any such budding stellar systems would face an uphill battle, developing only about two light-years from the galaxy’s central supermassive black hole with its intense gravity and ultraviolet radiation. But it’s not impossible for the small stars to survive in the hostile place, a new study suggests.

“Nature is very clever. It finds ways to work in extreme environments,” says Farhad Yusef-Zadeh, an astrophysicist at Northwestern University in Evanston, Ill. Four blobs of gas near the galactic center have the right amount of mass to be planetary systems with small, young stars, Yusef-Zadeh and colleagues report online January 20 at arXiv.org. The paper is also slated for publication in the Monthly Notices of the Royal Astronomical Society.
“It is fairly likely that planets and low-mass stars do form near the galactic center. But we do not know it for sure at the moment,” says Avi Loeb, an astrophysicist at Harvard University. Loeb, who was not involved in the study, says the new evidence is “tentative at best.”

Yusef-Zadeh and colleagues used ALMA, the Atacama Large Millimeter/submillimeter Array, in Chile to study emissions from five of the 44 blobs of gas that the team discovered in 2014 (SN Online: 3/24/15). Four of the clouds had between 0.03 and 0.05 as much mass as the sun, the team calculated. That’s right in line with what’s needed to generate low-mass stars — ones about the size of the sun or a little bigger — and the planets that orbit them, Yusef-Zadeh says. He points out that the team has not detected these stars or planets, just that conditions are ripe for them to exist.

Loeb notes that the team had to infer the clouds’ entire masses from the ALMA measurements, which may reveal only a surface look at the blobs. The clouds may actually be denser; as a result, they would form more massive stars, challenging the team’s claim that low-mass stars are forming.

Yusef-Zadeh and colleagues are planning additional studies with ALMA and are also working on research that suggests that black holes may, in fact, help star formation. “It’s paradoxical,” Yusef-Zadeh says. “Black holes eat everything that comes too close to them. They tear everything apart. But they may actually make the formation of stars more efficient.”

The breath of oxygen that enabled the emergence of complex life kicked off around 100 million years earlier than previously thought, new dating suggests.

Previous studies pegged the first appearance of relatively abundant oxygen in Earth’s atmosphere, known as the Great Oxidation Event, or GOE, at a little over 2.3 billion years ago. New dating of ancient volcanic outpourings, however, suggests that oxygen levels began a wobbly upsurge between 2.460 billion and 2.426 billion years ago, researchers report the week of February 6 in Proceedings of the National Academy of Sciences.

That time difference is a big deal, says study coauthor and sedimentary geologist Andrey Bekker of the University of California, Riverside. The new date shakes up scientists’ understanding of the environmental conditions that led to the GOE, which prompted the evolution of oxygen-dependent life-forms called eukaryotes. Voluminous volcanic eruptions at the time poured fresh rock over a supercontinent near the equator, and the planet dipped into a frigid period known as a Snowball Earth.

A similar series of geologic events around 700 million years ago coincided with a second rise of oxygen, to near-modern levels, and some eukaryotes evolving into the first animals. Both oxygen upswings pushed life toward complexity and the ultimate emergence of humans, Bekker says. “For the first time, we see parallels between these two time intervals,” he says.
Oxygen-producing microbes probably first appeared more than 3 billion years ago (SN Online: 9/8/15). But oxygen remained scant until the GOE when, for unknown reasons, atmospheric concentrations of the gas rose from near zero to around 0.1 percent of modern levels.

Dating the GOE’s start has been tricky, though, because few rocks from back then remain. Geologist Ashley Gumsley of Lund University in Sweden, Bekker and colleagues studied ancient volcanic rocks from South Africa that neighbor a layer of minerals that could have formed only in the presence of oxygen. Using an old technique, geologists had previously determined those volcanic rocks to be from around 2.222 billion years ago, well after the GOE’s start.

Applying modern techniques that measure the gradual decay of radioactive uranium in the rocks, the researchers revised the volcanism’s timing to about 2.426 billion years ago. That new date — plus a separate volcanic eruption previously dated to around 2.460 billion years ago that clearly happened before the oxygen rise — helps constrain the potential GOE start date.

The GOE isn’t the only global event to have its timeline tweaked. The oldest known evidence of global glaciation, called a Snowball Earth, lies underneath and alongside the South African rocks. The new eruption dating pushes that Snowball Earth event earlier as well — to around the same time as the start of the GOE.

The oxygen rise and the temperature drop may have been related, the researchers propose.

The new data and existing chemical evidence suggest that oxygen levels during the GOE wavered between pitiful and plentiful several times, rather than steadily rising (SN: 2/18/17, p. 16). (Oxygen concentrations stabilized around 2.250 billion years ago and remained largely unchanged until levels rose again more than a billion years later.) These oscillations coincided with Snowball Earths and volcanic eruptions, Gumsley says.

Climate, oxygen and volcanism were intertwined during the GOE, the researchers propose. Volcanic eruptions covered the supercontinent with fresh rock. That rock formed near the equator where heavy precipitation weathered the rock, drawing carbon dioxide from the air and washing nutrients into the ocean. Those nutrients nourished photosynthetic microbes, which produced an abundance of oxygen. Oxygen built up in the atmosphere and reacted with methane, reducing levels of that greenhouse gas (SN: 10/29/16, p. 17).

With less CO2 and methane warming the climate, Earth froze and oxygen-producing biological activity decreased. The ongoing volcanism spewed replacement CO2 into the atmosphere over time and eventually reheated the planet.

“This is further evidence that oxygen’s history has really been a roller coaster ride rather than a unidirectional rise,” says Yale University geochemist Noah Planavsky. While he’s uncertain about the role rock weathering played in controlling ancient oxygen levels, Planavsky believes the new age will allow scientists to delve into the question of why the GOE began when it did. “Without dates,” he says, it’s impossible “to have any real grounding to tackle these problems.”

People who undergo gastric bypass surgery are more likely to experience a remission of their diabetes than patients who receive a gastric sleeve or intensive management of diet and exercise, according to a new study. Bypass surgery had already shown better results for diabetes than other weight-loss methods in the short term, but the new research followed patients for five years.

“We knew that surgery had a powerful effect on diabetes,” says Philip Schauer of the Bariatric & Metabolic Institute at the Cleveland Clinic. “What this study says is that the effect of surgery is durable.” The results were published online February 15 in the New England Journal of Medicine.
The study followed 134 people with type 2 diabetes for five years in a head-to-head comparison of weight-loss methods. At the end of that time, two of 38 patients who only followed intensive diet and exercise plans were no longer in need of insulin to manage blood sugar levels. For comparison, 11 of 47 patients who had a gastric sleeve, which reduces the size of the stomach, and 14 of 49 who underwent gastric bypass, a procedure that both makes the stomach smaller and shortens digestion time, did not need the insulin anymore. In general, patients who had been diabetic for fewer than eight years were more likely to be cured, Schauer says.

Even those surgical patients who still needed to take insulin had greater weight loss and lower median glucose levels than others in the study. This study was also one of the few to show that bariatric surgery could help those with only mild obesity, defined as a body mass index between 27 and 34. How bariatric surgery might improve diabetes is still unknown, but scientists have pointed to effects on the body’s metabolism (SN: 8/24/13, p. 14) and gut microbes (SN: 9/5/15, p. 16).
The same research team had published similar results at one and three years after surgery, but few studies looked further, says Kristoffel Dumon, a bariatric surgeon with the University of Pennsylvania Health System in Philadelphia. “The criticism of bariatric research has been that there are no good long-term results. With weight-loss surgery, you often see rapid initial results, but you want to see that to a five-year time point.”
Dumon also notes that the patients who received only intensive medical therapy did not report an improvement in their quality of life, and their emotional well-being worsened. People in the surgical group reported improvements in quality of life, but not in emotional well-being, a finding that Schauer says has more to do with stress management and other characteristics that wouldn’t necessarily be affected by surgery.

Schauer hopes to have even longer-term data in the future. His team will combine their results with those from similar research at three other U.S. sites with the goal of following patients for up to 10 years.