The sun has been in the same routine for at least 290 million years, new research suggests.

Ancient tree rings from the Permian period record a roughly 11-year cycle of wet and dry periods, climate fluctuations caused by the ebbing and flowing of solar activity, researchers propose January 9 in Geology. The discovery would push back the earliest evidence of today’s 11-year solar cycle by tens of millions of years.

“The sun has apparently been doing what it’s been doing today for a long time,” says Nat Gopalswamy, a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., who was not involved in the study.
Around every 11 years, the sun’s brightness and the frequency of sunspots and solar flares completes one round of waxing and waning. These solar changes alter the intensity of sunlight reaching Earth and, some scientists hypothesize, may affect the composition of the stratosphere and rates of cloud formation. Those effects could alter rainfall rates, which in turn influence tree growth.

Ancient trees may hold clues to similar cycles from long ago. In what is now southeast Germany, volcanic eruptions buried an ancient forest under debris roughly 290 million years ago. Paleontologists Ludwig Luthardt and Ronny Rößler of the Natural History Museum in Chemnitz, Germany, identified tree rings in the fossilized remains of the trees.

Measuring the widths of the rings, which show how much the plants grew each year, the researchers discovered a cycle in growth rates. The cycle lasted on average 10.62 years. This cycle reflects years-long rises and falls in annual rainfall rates caused by the solar cycle, the researchers propose. The cycle’s average length falls within the 10.44-year to 11.16-year length of the sunspot cycle seen over the last few hundred years.

Whether the solar and tree ring cycles are connected isn’t certain, says paleoclimatologist Adam Csank of the University of Nevada, Reno. Many studies suggest that it is not possible to clearly identify sunspot cycles in modern tree ring records, he notes. Other changes in Earth’s climate system or periodic insect outbreaks might contribute to tree ring widths, he says.

BOSTON — A taste for reddish young leaves might have pushed howler monkeys toward full-spectrum color vision. The ability to tell red from green could have helped howlers pick out the more nutritious, younger leaves, researchers reported February 19 at the annual meeting of the American Association for the Advancement of Science. That’s a skill their insect-eating close relatives probably didn’t need.

Primates show substantial variation in their color vision capabilities, both between and within species, said Amanda Melin, a biological anthropologist at the University of Calgary in Canada. Trichromatic vision (how most humans see) requires three light-sensitive proteins in the eye that can detect different wavelengths of light. Within most monkey species in Central and South America, only some individuals have trichromatic vision. Males have dichromatic vision — they’re red-green colorblind — and only some females can see the whole rainbow. Howlers are an exception — thanks to a duplicated gene on their X chromosomes, trichromatic vision is the norm for both males and females.
Howlers graze on leaves from Ficus trees and other plants when fruit can’t be found. In field observations of mantled howlers (Alouatta palliata) in Costa Rica, the monkeys preferentially munched on the younger, more nutritious leaves, Melin’s team found. The reddish hue of new leaves makes them pop more when seen with trichromatic vision than dichromatic vision, the researchers reported in a paper accepted for publication in Ecology and Evolution. Because young leaves are a fleeting treat and not a constant resource, monkeys able to spot them more quickly could have had a selective advantage.

Similar selection pressures might also help explain why Old World monkeys from Asia and Africa also have consistent trichromatic vision, Melin said. “What we might be seeing is a convergent evolution for animals who fall back on leaves when fruit isn’t around.”

On the other hand, other Central and South American monkeys usually go for insects, instead of leaves, when there’s no fruit. Dichromatic vision might be a better fit for their lifestyle, Melin said. “Color can impede ability to see patterns, borders and textures. Insects hide and camouflage.”

With a final rip, an iceberg roughly the size of Delaware has broken off Antarctica’s Larsen C ice shelf. Anticipated for weeks, the fracture is one of the largest calving events ever recorded.

On July 12, satellite images confirmed a nearly 5,800-square-kilometer, 1-trillion-metric-ton chunk of ice, equivalent to 12 percent of Larsen C’s total area, split from the ice shelf. “[We] have been surprised how long it took for the rift to break through the final few kilometers of ice,” Adrian Luckman, a glaciologist at Swansea University in Wales, said in a blogpost for Project MIDAS, which has been tracking the effects of a warming climate on the ice shelf. Now the focus will shift to the stability of the remaining ice shelf and the fate of the giant iceberg.
Scientists had been monitoring Larsen C since 2014, when they noticed that a crack in the ice shelf had grown roughly 20 kilometers in less than nine months (SN: 7/25/15, p. 8). After a relative lull in 2015, the crack grew another 40 kilometers in 2016 and then 10 more in the first half of January 2017, bringing its total length to 175 kilometers. At that point, its tip was 20 kilometers from the Weddell Sea.
The crack grew another 17 kilometers between May 25 and May 31 — at times traveling parallel to the edge and ultimately putting it within 13 kilometers of the ice front. Then, in late June, the outer part of the ice shelf picked up speed, putting new pressure on the crack and the entire shelf. “It won’t be long now,” Project Midas tweeted June 30. Added Luckman, also in a tweet: “The remaining ice is strained near to breaking point.”

Yet the vigil lasted nearly two more weeks. By July 6, the crack had come within 5 kilometers of the edge of the ice. Then, sometime between July 10 and July 12, it finally reached the water, allowing the huge hunk of ice to splinter off into the sea.
The ice loss dramatically alters the landscape of Larsen C, Luckman notes. “Maps will need to be redrawn.” And that could be the least of the trouble ahead, says Adam Booth, a geophysicist at the University of Leeds in England also with Project MIDAS. “The calving event is significant because it is likely a precursor to something much bigger, potentially the collapse of the whole Larsen C ice shelf,” Booth says. The same thing happened to the neighboring Larsen B ice shelf in 2002, after it calved a Rhode Island-sized iceberg (SN: 3/30/02, p. 197).

“Glaciologists are keen to see how Larsen C will react,” says Luckman.

A complete collapse of Larsen C could have implications for sea level rise. Antarctica’s ice shelves act as buttresses, helping to slow the flow of the continent’s ice into the ocean. Since these shelves float on the water, calving icebergs don’t directly raise sea level. But calving or the collapse of an ice shelf allows glaciers and ice streams further inland to flow into the ocean, which can contribute to sea level rise.

Calving of icebergs is common, and over several decades, the shelves usually recover to their original size. But in the last two decades, ice shelves have instead continued to lose ice until collapsing, probably as a result of rising temperatures due to climate change, researchers suspect. In 2014, researchers concluded the collapse of Larsen B was the result of warming (SN: 10/18/14, p. 9).

Some computer simulations suggest Larsen C could suffer the same fate, possibly within a few years to decades, Luckman says. Still, the calving event that feeds a potential collapse may be hard to pin on climate change. “Not all ice-related stories have a clear global warming origin,” Luckman notes. Larsen C’s calving, he says, “may simply be a natural event that would have happened regardless of human activity.”
Not everyone is convinced that Larsen C will fall apart completely. Researchers from Europe predict major changes to the shelf would happen only if it loses 55 percent of its ice. At that point, a significant amount of ice could ooze from glaciers into the ocean. Still, understanding what allowed the recent rift to grow and calve will “give us insight regarding other fractures or rifts on the shelf,” says geoscientist Dan McGrath of Colorado State University in Fort Collins. While McGrath says a collapse is “very unlikely,” he adds that “these other dormant rifts are in locations where if they reinitiated, the subsequent calving event would be worrisome for the shelf’s stability.”

Discrepancies in the predictions of Larsen C’s fate raise an important point, says Richard Alley, a geologist at Penn State. Researchers don’t understand ice shelf calving and collapsing enough predict how any one individual ice shelf will behave after a break.

“The Larsen C ice shelf is, of course, just one small part of Antarctica,” Booth says. “What is worrying is that we’re seeing trends in several ice shelves that tend towards decreasing stability. Should they continue along these trends, we could be seeing the start of increased mass loss from the Antarctic continent.”

Early in Inferior, science writer Angela Saini recalls a man cornering her after a signing for her book Geek Nation, on science in India. “Where are all the women scientists?” he asked, then answered his own question. “Women just aren’t as good at science as men are. They’ve been shown to be less intelligent.”

Saini fought back with a few statistics on girls’ math abilities, but soon decided that nothing she could say would convince him. It’s a situation that may feel familiar to many women. “What I wish I had was a set of scientific arguments in my armory,” she writes.
So she decided to learn the truth about what science really does tell us about differences between the sexes. “For everyone who has faced the same situation,” she writes, “the same desperate attempt to not lose control but have at hand some real facts and a history to explain them, here they are.”

In Inferior, Saini marshals plenty of facts and statistics contradicting sexist notions about women’s bodies and minds. She cites study after study showing little or no difference in male and female capabilities.

But it’s the book’s historical perspective that makes it most compelling. Only by understanding the cultural context of the men whose studies and ideas first pointed to gender imbalances can we see how deeply biases run, Saini argues.

Charles Darwin’s influential ideas reflected his times, for instance. In The Descent of Man, he wrote that “man has ultimately become superior to woman” via evolution. To a woman active in her local women’s movement, Darwin wrote, “there seems to me to be a great difficulty from the laws of inheritance … in [women] becoming the intellectual equals of man.”

If that idea sounds absurd now, don’t fool yourself into thinking it has vanished. Saini’s book is full of examples right up to today of scientists who have started from this and other flawed premises, which have led to generations of flawed studies and results that reinforce stereotypes. But the tide has been turning, as more women have entered science and more scientists of both sexes seek to remove bias from their work.
Saini does an excellent job of dissecting research on evolution, neuroscience and even the long-standing notion that women’s sexual behavior is driven by their interest in stable, monogamous relationships. By the end, it’s clear that science doesn’t divide men and women; we’ve done that to ourselves. And as scientists become more rigorous, we get closer to seeing ourselves as we really are.

Some ants have figured out how to keep from getting lost: Build taller anthills.

Desert ants that live in the hot, flat salt pans of Tunisia spend their days looking for food. Successful grocery runs can take the insects as far as 1.1 kilometers from their nests. So some of these ants build towering hills over their nests that serve as a landmark to guide the way home, researchers report in the July 10 Current Biology.
“I am surprised and fascinated that ants have visual acuity at the distances implied in this work,” says ecologist Judith Bronstein of the University of Arizona in Tucson who wasn’t involved in the new study. It “also implies that ants regularly assess the complexity of their local habitat and change their decisions based on what they conclude about it.”

Desert ants (Cataglyphis spp.) use a navigation system called path integration, relying on the sun’s position and counting their steps to keep track of where they are relative to their nest (SN: 1/19/17). But this system becomes increasingly unreliable as distance from the nest increases. Like other types of ants, desert ants also rely more generally on sight and smell. But the vast, almost featureless salt pans look nearly the same in every direction.

“We realized that, whenever the ants in salt pans came closer to their nest, they suddenly pinpointed the nest hill … from several meters distance,” says Markus Knaden, a neuroethologist at Max Planck Institute for Chemical Ecology in Jena, Germany. “This made us think that the hill functions as a nest-defining landmark.”

So Knaden and colleagues captured ants (C. fortis) from nests in the middle of salt pans and from along their shorelines. Only nests from the salt pan interiors had distinct hills, which can be up to 40 centimeters tall, whereas the hills on shoreline nests were lower or barely noticeable.
Next, the team removed any hills and placed the captured insects some distance away from their nests. Ants from the salt pans’ interiors struggled more than shore ants to find home. Since the shore ants were adept at using the shoreline for guidance, they weren’t as affected by the hill removal, the researchers conclude.

The team wanted to know if the ants were deliberately building a taller hill when their surroundings lacked any visible landmark. So, the researchers removed the hills of 16 salt pan nests and installed two 50-centimeter-tall black cylinders apiece near eight of them. The other eight nests were left without any artificial visual aid.
After three days, the researchers found that ants from seven of the unaided nests had rebuilt their hills. But ants from only two of the nests with cylinders had bothered to rebuild.

“These desert ants already told us about path integration and step counting for orientation…. But this business of building your own visual landmark, incredible,” says entomologist John Longino of the University of Utah in Salt Lake City who wasn’t involved in the research. “Are they sitting down to a council meeting to decide whether they need a bigger landmark? Is this somehow an evolved behavior in this one desert ant species?”

For now, it’s unclear how the ants decide to build, or not to build, a hill. Interestingly, nest building is usually performed by younger ants that are not foragers yet, Knaden says, and have not experienced the difficulty in finding a nest in the absence of a hill. That means there is an exchange of information between the veteran foraging ants and their novice nest mates, he says.

Bronstein also wonders about the risks of building the taller structures. Such risks “are implied by the fact that the ants don’t build such a structure where it isn’t needed,” she says. But, “for instance, isn’t it a clear cue to ant predators that food can be found there?”