Long before humans domesticated other animals, we may have domesticated ourselves.

Over many generations, some scientists propose, humans selected among themselves for tameness. This process resulted in genetic changes, several recent studies suggest, that have shaped people in ways similar to other domesticated species.

Tameness, says evolutionary biologist and primatologist Richard Wrangham of Harvard University, may boil down to a reduction in reactive aggression — the fly-off-the-handle temperament that makes an animal bare its teeth at the slightest challenge. In this sense, he says, humans are fairly tame. We might show great capacity for premeditated aggression, but we don’t attack every stranger we encounter.
Sometime in the last 200,000 years, humans began weeding out people with an overdose of reactive aggression, Wrangham suggests. Increasingly complex social skills would have allowed early humans to gang up against bullies, he proposes, pointing out that hunter-gatherers today have been known to do the same. Those who got along, got ahead.

Once animals have been selected for tameness, other traits tend to follow, including reshaping of the head and face. Humans even look domesticated: Compared with Neandertals’, our faces are shorter with smaller brow ridges, and males’ faces are more similar to those of females.
Selecting for less-aggressive humans could have also helped us flourish as a social species, says Antonio Benítez-Burraco, who studies language evolution at the University of Huelva in Spain. The earliest Homo sapiens were becoming capable of complex thought, he proposes, but not yet language. “We were modern in the sense of having modern brains, but we were not modern in behavior.”
Once humans began to self-­domesticate, though, changes to neural crest cells could have nudged us toward a highly communicative species. Something similar happens in songbirds: Domesticated birds have more complex songs than their wild counterparts. What’s more, self-domestication may be more common than once thought. Bonobos, Wrangham notes, live in peaceful groups compared with closely related, but more violent, chimpanzees. If humans took steps to domesticate themselves, perhaps they weren’t the only ones.

Cabbage-chomping moths genetically modified to be real lady-killers may soon take flight in upstate New York. On July 6, the U.S. Department of Agriculture OK’d a small open-air trial of GM diamondback moths (Plutella xylostella), which the agency says do not pose a threat to human or environmental health.

These male moths carry a gene that kills female offspring before they mature. Having fewer females available for mating cuts overall moth numbers, so releasing modified male moths in crop fields would theoretically nip an outbreak and reduce insecticide use.
Originally from Europe, diamondback moths have quite the rap sheet: They’re invasive, insecticide-resistant crop pests. The caterpillar form munches through cauliflower, cabbage, broccoli and other Brassica plant species across the Americas, Southeast Asia, Australia and New Zealand.

After completing successful lab and cage trials, Cornell University entomologist Tony Shelton and colleagues now plan to loose the moths on 10 acres of Brassica fields at the New York State Agricultural Experiment Station in Geneva. The team has clearance to release 10,000 moths at a time, and up to 30,000 weekly.

This GM strain comes from Oxitec, the same firm behind controversial GM mosquitoes proposed for release in Florida (SN Online: 8/5/16). Several agricultural and environmental groups oppose the moth trial, too. While these will be the first GM moths released with a so-called female lethality gene, this won’t be the first genetically modified moth released in the United States. In 2009, researchers in Arizona tested transgenic pink bollworm moths, which threaten cotton fields.

The trial’s exact timeline remains up in the air. The scientists need approval from the New York State Department of Environmental Conservation before going forward.

Give Homo naledi credit for originality. The fossils of this humanlike species previously revealed an unexpectedly peculiar body plan. Now its pockmarked teeth speak to an unusually hard-edged diet.

H. naledi displays a much higher rate of chipped teeth than other members of the human evolutionary family that once occupied the same region of South Africa, say biological anthropologist Ian Towle and colleagues. Dental damage of this kind results from frequent biting and chewing on hard or gritty objects, such as raw tubers dug out of the ground, the scientists report in the September American Journal of Physical Anthropology.
“A diet containing hard and resistant foods like nuts and seeds, or contaminants such as grit, is most likely for H. naledi,” says Towle, of Liverpool John Moores University in England.

Extensive tooth chipping shows that “something unusual is going on” with H. naledi’s diet, says paleoanthropologist Peter Ungar of the University of Arkansas in Fayetteville. He directs ongoing microscopic studies of H. naledi’s teeth that may provide clues to what this novel species ate.
Grit from surrounding soil can coat nutrient-rich, underground plant parts, including tubers and roots. Regularly eating those things can cause the type of chipping found on H. naledi teeth, says paleobiologist Paul Constantino of Saint Michael’s College in Colchester, Vt. “Many animals cannot access these underground plants, but primates can, especially if they use digging sticks.”
H. naledi fossils, first found in South Africa’s subterranean Dinaledi Chamber and later a second nearby cave (SN: 6/10/17, p. 6), came from a species that lived between 236,000 and 335,000 years ago. It had a largely humanlike lower body, a relatively small brain and curved fingers suited for climbing trees.

Towle’s group studied 126 of 156 permanent H. naledi teeth found in Dinaledi Chamber. Those finds come from a minimum of 12 individuals, nine of whom had at least one chipped chopper. Two of the remaining three individuals were represented by only one tooth. Teeth excluded from the study were damaged, had not erupted above the gum surface or showed signs of having rarely been used for chewing food.

Chips appear on 56, or about 44 percent, of H. naledi teeth from Dinaledi Chamber, Towle’s team says. Half of those specimens sustained two or more chips. About 54 percent of molars and 44 percent of premolars, both found toward the back of the mouth, display at least one chip. For teeth at the front of the mouth, those figures fell to 25 percent for canines and 33 percent for incisors.

Chewing on small, hard objects must have caused all those chips, Towle says. Using teeth as tools, say to grasp animal hides, mainly damages front teeth, not cheek teeth as in H. naledi. Homemade toothpicks produce marks between teeth unlike those on the H. naledi finds.

Two South African hominids from between roughly 1 million and 3 million years ago, Australopithecus africanus and Paranthropus robustus, show lower rates of tooth chipping than H. naledi, at about 21 percent and 13 percent, respectively, the investigators find. Researchers have suspected for decades that those species ate hard or gritty foods, although ancient menus are difficult to reconstruct (SN: 6/4/11, p. 8). Little evidence exists on the extent of tooth chipping in ancient Homo species. But if H. naledi consumed underground plants, Stone Age Homo sapiens in Africa likely did as well, Constantino says.

In further tooth comparisons with living primates, baboons — consumers of underground plants and hard-shelled fruits — showed the greatest similarity to H. naledi, with fractures on 25 percent of their teeth. That figure reached only about 11 percent in gorillas and 5 percent in chimpanzees.

Human teeth found at sites in Italy, Morocco and the United States show rates and patterns of tooth fractures similar to H. naledi, he adds. Two of those sites date to between 1,000 and 1,700 years ago. The third site, in Morocco, dates to between 11,000 and 12,000 years ago. People at all three sites are suspected to have had diets unusually heavy on gritty or hard-shelled foods, the scientists say.

Chips mar 50 percent of H. naledi’s right teeth, versus 38 percent of its left teeth. That right-side tilt might signify that the Dinaledi crowd were mostly right-handers who typically placed food on the right side of their mouths. But more fossil teeth are needed to evaluate that possibility, Towle cautions.

Some stars erupt like clockwork. Astronomers have tracked down a star that Korean astronomers saw explode nearly 600 years ago and confirmed that it has had more outbursts since. The finding suggests that what were thought to be three different stellar objects actually came from the same object at different times, offering new clues to the life cycles of stars.

On March 11, 1437, Korean royal astronomers saw a new “guest star” in the tail of the constellation Scorpius. The star glowed for 14 days, then faded. The event was what’s known as a classical nova explosion, which occurs when a dense stellar corpse called a white dwarf steals enough material from an ordinary companion star for its gas to spontaneously ignite. The resulting explosion can be up to a million times as bright as the sun, but unlike supernovas, classical novas don’t destroy the star.
Astronomer Michael Shara of the American Museum of Natural History in New York City and colleagues used digitized photographic plates dating from as early as 1923 to trace a modern star back to the nova. The team tracked a single star as it moved away from the center of a shell of hot gas, the remnants of an old explosion, thus showing that the star was responsible for the nova. The researchers also saw the star, which they named Nova Scorpii AD 1437, give smaller outbursts called dwarf novas in the 1930s and 1940s. The findings were reported in the Aug. 31 Nature.

The discovery fits with a proposal Shara and colleagues made in the 1980s. They suggested that three different stellar observations — bright classical nova explosions, dwarf nova outbursts and an intermediate stage where a white dwarf is not stealing enough material to erupt — are all different views of the same system.

“In biology, we might say that an egg, a larva, a pupa and a butterfly are all the same system seen at different stages of development,” Shara says.

A bit of imperfection could be perfect for flowers creating a “blue halo” effect that bees can see.

At least a dozen families of flowering plants, from hibiscuses to daisy relatives, have a species or more that can create a bluish-ultraviolet tinge using arrays of nanoscale ridges on petals, an international research team reports online October 18 in Nature. These arrays could be the first shown to benefit from the sloppiness of natural fabrication, says coauthor Silvia Vignolini, a physicist specializing in nanoscale optics at the University of Cambridge.
Flowers, of course, can’t reach industrial standards for uniform nanoscale fabrication. Yet the halo may be a case where natural imperfections may be important to a flower’s display. Tests with artificial flowers showed that the nanoglitches made it easier for bees to learn that a showy petal meant a sugary reward, Vignolini and colleagues found.
Blues are rare in actual pigments in living things( SN: 12/10/16, p. 4 ). Color in the wings of Morpho butterflies or blue jay feathers, for instance, comes from nanoscale structures that contain no pigments but create colorful illusions by muting some wavelengths of light while intensely reflecting others ( SN: 6/11/16, p. 32 ).
Flower petals make their blue halo illusion with somewhat irregular versions of what are called diffraction gratings, rows of ridges like the recording surface on a CD. A perfectly regular array of ridges would create true iridescence, changing color depending on the angle a viewer takes. The flowers’ imperfections, variations in ridge height and spacing, weaken or destroy the iridescence. A viewer swooping by would see less color shifting and more of a bluish-ultraviolet tinge reflected at a wider range of angles.

To see whether bees respond more to iridescence or a blue halo, researchers created sets of artificial flowers, pieces of epoxy resin with some kind of nanoscale-ridged array. A petal-scale project was huge compared with the usual nanoscale experiments, requiring marathon fabrication sessions. “We were a pain to everybody,” Vignolini says.

In two tests, researchers offered bumblebees a pair of “flowers,” one that held sugar water and one with a nasty-tasting solution, to see how quickly bees would learn to distinguish sweet from foul. When the flower’s nanoridges had imperfections creating a blue halo, bees learned the task faster than when the flower had perfect iridescence. Imperfect arrays were actually an advantage for the flowers in creating displays pollinating bees find memorable, the researchers conclude.
Such disorder in nature’s structural color (versus pigments) has shown up before, as in obviously jumbled color-trick structures in bird feathers. Before the tests, though, it was unclear whether flowers would benefit from perfect iridescence and were just falling short in growing perfect arrays. The blue halo might have been merely a side effect of challenging botanical fabrication. The bee experiments, however, showed the opposite, the researchers say. These are the first tests to show that some disorder is not just a downside of natural fabrication but in itself “has a function,” Vignolini says.

That result makes sense to visual ecologist Nathan Morehouse of the University of Cincinnati. Nanostructures that iridesce may often just be a way birds or butterflies can create an unusual color rather than a way to produce iridescence for its own sake. The shifting colors might even have a downside. By definition, true iridescence changes color as an insect or bird changes its angle of approach, and so may not be the best form for an easy-to-remember signal. “Iridescence itself is something they just have to manage,” he suggests.