People hunted and foraged year-round in the thin air of China’s Tibetan Plateau at least 7,400 to 8,400 years ago, a new study suggests. And permanent settlers of the high-altitude region might even have arrived as early as 12,000 to 13,000 years ago.

Three lines of dating evidence indicate that humans occupied the central Tibetan Plateau’s Chusang site, located more than 4,000 meters above sea level, at least 2,200 years earlier than previously thought, say geologist Michael Meyer of the University of Innsbruck in Austria and colleagues. Their report, published in the Jan. 6 Science, challenges the idea that the Tibetan Plateau lacked permanent settlers until farming groups arrived around 5,200 years ago.、
“Hunter-gatherers permanently occupied the Tibetan Plateau by around 8,000 years ago, which coincided with a strong monsoon throughout Asia that created wet conditions on the plateau,” Meyer says.

These early permanent residents hunted animals such as wild yaks and foraged for edible plants, including berries from sea buckthorn shrubs, in nearby river valleys at elevations more than 3,600 meters above sea level, Meyer suspects. Brief, summer forays to Chusang would have been difficult for people living below 3,300 meters above sea level, he adds. Even when mountain passes were clear of heavy snowfall and expanding valley glaciers, round trips from low altitudes to the central Tibetan Plateau would have taken 41 to 70 days, Meyer’s team estimates.

Researchers discovered Chusang in 1998. The site consists of 19 human hand- and footprints on the surface of a fossilized sheet of travertine, a form of limestone deposited there by water from a hot spring.
The new age estimates for Chusang come from three measures: the decay rate of forms of radioactive thorium and uranium in travertine sampled in and around the prints; determinations of the time since quartz crystals extracted from the travertine were last exposed to sunlight; and radiocarbon measures of sediment and microscopic plant remains found on the travertine slab’s surface.
Signs of long-term camping at Chusang have yet to turn up, but extensive excavations of the site have not been conducted, Meyer says. His group found chipped rocks and other stone tool‒making debris at two spots near Chusang’s hot springs. These finds are undated.

Previous research has suggested that hunter-gatherers occasionally reached the Tibetan Plateau’s northern edge by around 12,000 years ago (SN: 7/7/01, p. 7), and again from about 8,000 to 6,000 years ago, says archaeologist Loukas Barton of the University of Pittsburgh, who wasn’t involved in the study. But the new discoveries at Chusang may not necessarily point to permanent residence there. Those early arrivals likely spent a single summer or a few consecutive years at most on the plateau, Barton says. “That would not constitute a peopling of a region any more than our 1969 visit to the moon did,” he says.

Archaeological finds indicate that human populations expanded on the Tibetan Plateau between around 5,200 and 3,600 years ago, Barton says. Those groups cultivated barley and wheat at high altitudes and herded domesticated sheep and perhaps yaks, he says.

Before that time, Chusang might have supported a year-round occupation, says archaeologist David Rhode of the Desert Research Institute in Reno, Nev., who wasn’t involved in the study. But the site could easily have been occupied seasonally, he says. Unlike Meyer, Rhode estimates that Chusang was about a two-week walk from some lower-altitude campsites. “That’s not far at all for a human forager.”

New dates for Chusang also raise the possibility that rare gene variants that aid survival in high-altitude, oxygen-poor locales first evolved among hunter-gatherers on the Tibetan Plateau, Meyer says. But both Barton and Rhode doubt it.

Heroin cure works

[T]he drug methadone appears to have fulfilled its promise as an answer to heroin addiction. Some 276 hard-core New York addicts … have lost their habits and none have returned to heroin — a 100 percent success rating. Methadone, a synthetic narcotic, acts by blocking the euphoric effect of opiates. Addicts thus get nothing from heroin and feel no desire to take it. — Science News. February 4, 1967.

UPDATE:
The U.S. Food and Drug Administration approved methadone as a treatment for opiate addiction in 1972 but quickly recognized that it was no panacea. That same year, policy makers worried that methadone would produce addicts — as patients got high off the treatment itself (SN: 10/28/72, p. 277). Methadone can be deadly: In 2014, 3,400 people died of methadone overdoses. Although methadone is still used, drugs such as buprenorphine and naltrexone have joined the treatment arsenal for opiate addiction.

Electronic cigarettes may increase the risk of heart disease, researchers at UCLA report.

The team found that two risk factors for heart disease were elevated in 16 e-cigarette users compared with 18 nonsmokers.

“The pattern was spot-on” for what has been seen in heart attack patients and those with heart disease and diabetes, says cardiologist Holly Middlekauff, a coauthor of the study published online February 1 in JAMA Cardiology.

But because the study only looked at a small number of people, the results are not definitive — just two or three patients can skew results, John Ambrose, a cardiologist with the University of California, San Francisco cautions. Plus, he says, some of the e-cigarette users in the study used to smoke tobacco, which may have influenced the data.
Even so, Ambrose called the study interesting, noting that “the medical community just doesn’t have enough information” to figure out if e-cigarettes are dangerous.

E-cigarette users in the study had heartbeat patterns that indicated high levels of adrenaline — also known as epinephrine — in the heart, a sign of heart disease risk. Researchers also found signs of increased oxidative stress, an imbalance of certain protective molecules that can cause the hardening and narrowing of arteries.

Previous research has connected oxidative stress to e-cigarettes. The new study targeted where it might occur and how it could contribute to heart disease, says Aruni Bhatnagar of the American Heart Association Tobacco Regulation and Addiction Center based at the University of Louisville in Kentucky.

This study “adds to the case that there may be some residual harm associated with e-cigarettes,” says Bhatnagar, whose editorial on e-cigarettes and heart risk appears in the same issue of JAMA Cardiology.

Previous studies have linked e-cigarettes to lung inflammation (SN: 7/12/14, p. 20) and examined the toxicity of e-cigarette vapor (SN: 8/20/16, p. 12).
Nicotine, the addictive substance found in both tobacco and electronic cigarettes, is known to elevate adrenaline levels. To ensure that they were measuring the long-term effects of vaping and not just the presence of nicotine, the researchers had their subjects refrain from using e-cigarettes the day of the tests.

The findings are important, Middlekauff says, because they show that e-cigarette users’ hearts are in “flight or fight” mode all the time, not just when they are smoking.

The next step is to nail down exactly what in e-cigarettes is responsible for these effects on the heart, Middlekauff says. The researchers also want to compare e-cigarettes’ effects on the heart with tobacco cigarettes’.

“Electronic cigarettes aren’t harmless,” Middlekauff says. “They have real, measurable physiological effects and these physiological effects, at least the couple that we found, have been associated with heart disease.”

Genetic methods for counting new species may be a little too good at their jobs, a new study suggests.

Computer programs that rely on genetic data alone split populations of organisms into five to 13 times as many species as actually exist, researchers report online January 30 in Proceedings of the National Academy of Sciences. These overestimates may muddy researchers’ views of how species evolve and undermine conservation efforts by claiming protections for species that don’t really exist, say computational evolutionary biologist Jeet Sukumaran and evolutionary biologist L. Lacey Knowles.
The lesson, says Knowles, “is that we shouldn’t use genetic data alone” to draw lines between species.

Scientists have historically used data about organisms’ ecological distribution, appearance and behavior to classify species. But the number of experts in taxonomy is dwindling, and researchers have turned increasingly to genetics to help them draw distinctions. Large genetic datasets and powerful computer programs can quickly sort out groups that have become or are in the process of becoming different species. That’s especially important in analyzing organisms for which scientists don’t have much ecological data, such as insects in remote locations or recently extinct organisms.

Knowles and Sukumaran, both of the University of Michigan in Ann Arbor, examined a commonly used computer analysis method, called multispecies coalescent, which picks out genetic differences among individuals that have arisen recently in evolutionary time. Such differences could indicate that a population of organisms is becoming a separate species. The researchers used a set of known species and tested the program’s ability to correctly predict the right number of species given certain variables. The program is good — maybe too good — at detecting the differences, Knowles says. If scientists don’t take other factors, such as geographical separation, into account, they may call genetically different groups separate species when they are merely subgroups of the same species.

Then again, it depends on what you mean by a “species,” says Rampal Etienne, an evolutionary community ecologist at the University of Groningen in the Netherlands. He developed the method that Knowles and Sukumaran analyzed. By one definition, a species is a genetically distinct lineage. “If that’s your species concept then, no, it’s not true that there are more species discovered by this method than there actually are,” Etienne says.

Biologists have long defined species primarily based on mating behavior and physical traits, not genetic similarity. Species are said to be reproductively isolated when they don’t mate either because they can’t or because they don’t for some reason (such as female fish choosing to mate with only red or blue males). Reproductive isolation doesn’t exclude two species from mating once in a while, says evolutionary biologist Ole Seehausen of the University of Bern in Switzerland. What’s important is that species that breed in the same area remain distinct.
What’s more, “speciation is not a one-way road,” Seehausen says. When ecological conditions change, groups that had been going their separate ways may breed with each other again. For instance, female fish that choose mates based on color may breed with males of the non-preferred color when water becomes murky and obscures their vision. Computer programs can predict when speciation has started but can never forecast whether the groups will remain separate or will come back together, Seehausen says.

Using the biological criteria, the genetic method may seem to fall short, but genetic analyses simply aren’t designed to address such questions, Seehausen says. He agrees with Knowles and Sukumaran that genetic data should be used in combination with ecological and other studies to identify species.

Characterizing species based on their genes could still be a useful conservation tool, Etienne says, helping to preserve genetic diversity. A diverse set of genes can help a species adapt to changing environments, and a lack of diversity can doom it to extinction. Identifying diverse groups within a population could help researchers decide where to focus conservation efforts, Etienne says. “Whether they are two species or not is less important,” he says.

Estimates of global biodiversity are not affected by any shortcomings with the genetic analysis programs, Knowles says. Scientists use many types of data to determine the total number of species in a region or on Earth.

A cautionary tale in evolutionary theory is coming straight from the horse’s mouth. When ancient horses diversified into new species, those bursts of evolution weren’t accompanied by drastic changes to horse teeth, as scientists have long thought.

A new evolutionary tree of horses reveals three periods when several new species emerged, scientists report in the Feb. 10 Science. The researchers found that changes in teeth morphology and body size didn’t change very much during these periods of rapid speciation.
“This knocks traditional notions that rapid diversification of new species comes with morphological diversification as well,” says paleontologist Bruce MacFadden of the University of Florida in Gainesville. “This is a very sophisticated and important paper.”

The emergence of several new species in a relatively short time is often accompanied by the evolution of special new traits. Classic notions of evolution say that these traits — such as longer teeth with extensive enamel — are adaptive, enabling an animal to succeed in a particular environment. In horses, the evolution of such teeth might permit a shift from browsing on leafy, shrubby trees to grazing on grasses in open spaces with windblown dust and grit.

“You can’t live on a grassland as a grazer and have short teeth,” says MacFadden, an expert in horse evolution. “You’ll wear your teeth down and that’s not a recipe for success as a species.”

Similarly, a big change in body size can indicate a move to a new environment. Animals that live in forests tend to be smaller and more solitary than the larger herd animals that live in open grasslands.

Paleontologist Juan Cantalapiedra and colleagues compiled decades of previous work to create an evolutionary tree of 138 horse species (seven of which exist today), spanning roughly 18 million years. The tree reveals three major branchings of new species: a North American burst between 15 million and 18 million years ago, and two bursts coinciding with dispersals into Eurasia about 11 million and 4.5 million years ago.
The researchers expected to see evidence of an “adaptive radiation,” major changes in teeth and body size that allowed the new horse species to succeed. But rates of body size evolution didn’t differ much in sections of the family tree with low and high speciation rates. And rates of change in tooth characteristics were actually lower in sections of the tree with fast speciation rates, the team reports.

“It’s very tempting to see some change in body size, for example, and say, ‘Oh, that’s adaptive radiation,’” says Cantalapiedra, of the Leibniz Institute for Evolution and Biodiversity Science at the Museum für Naturkunde in Berlin. “But that’s not what we see.”

Cantalapiedra and his collaborators speculate that during the periods of rapid speciation, the environment was so expansive and productive that there just wasn’t a lot of competition to drive the evolution of adaptive traits. Perhaps, for example, North American grasslands were so rich and dense that there was enough energy for various species to evolve without having to develop traits that gave them an edge.

That scenario might be special to horses, says MacFadden, but it might not. Similarly, classic adaptive radiation scenarios might be true in many cases, but as this work shows, not always.

BOSTON — Rooted in place, plants can’t run away from arsenic-tainted soil — but they’re far from helpless. Scientists have identified enzymes that help rice plant roots tame arsenic, converting it into a form that can be pushed back into the soil. That leaves less of the toxic element to spread into the plants’ grains, where it can pose a health risk to humans, researchers reported February 17 at the annual meeting of the American Association for the Advancement of Science.

Once arsenic worms its way into rice plant roots and gets into the vascular system, “it’s transported into the leaves and the grain,” David Salt, a biologist at the University of Nottingham in England who conducted the recent research, said during a news conference. Inside the plant, arsenic “can accumulate to levels where it can potentially be toxic if it accumulates over long times.”
Since arsenic occurs naturally in soil, understanding the genetic basis for plants’ natural defense mechanisms might help researchers engineer plants that take in less arsenic, said Mary Lou Guerinot, a biologist at Dartmouth College.
Arsenic in the soil switches between two different forms — ions with different electric charges. That form depends on soil conditions, which in a rice field fluctuate between wetter and drier. Plants are more likely to pull in arsenite from the soggy soil of a flooded rice paddy, and arsenate when that soil dries out a bit. The plants use different chemical mechanisms to take in and process the different arsenic ions.

In arsenate-rich soil, the ion sneaks into the outer layer of root cells through specialized passageways, called transport channels, that normally carry phosphate ions through root cell membranes. Transforming arsenate into arsenite lets the roots push the element back into the soil through a process called efflux, but scientists weren’t sure how the plant changed arsenic’s form.
Salt’s team found that rice plants without working genes for enzymes called HAC1;1 and HAC1;2 couldn’t turn arsenate into arsenite. So more arsenate accumulated in the plants’ shoots. When the scientists made HAC1;1 and HAC1;2 genes in other rice plants produce more of the enzymes than usual, grains from those plants had lower concentrations of any form of arsenic.

It’s just one defense of many, Salt said, and it’s not bulletproof. Arsenate can still spread into plants’ vascular systems from the roots via phosphate channels.

When the soil is rich in arsenite, rice roots take arsenite up through the same channels that take in silicon. Although efflux is an efficient way for roots to get rid of arsenite, there’s a limit to how quickly the cells can push the ion out.

So to create rice plants that are better at dealing with arsenic, Salt and other scientists are looking not just at how roots push out arsenic once it gets in, but how they keep the toxin out to begin with. For example, engineering channels that are better at pulling in just phosphate or just silicon could lessen the amount of arsenic that co-opts those channels.

Since soil conditions in a rice field switch between dry and wet, plants need defense mechanisms for both forms of arsenic. “Once we know what forms the plant takes in and how it’s doing that, we’ll need a solution for arsenate and arsenite,” Guerinot says. “There’s no easy fix.”

Certain birth defects were 20 times more prevalent in babies born to Zika virus–infected mothers in the U.S. in 2016 than they were before the virus cropped up in the United States, a CDC study suggests. The finding strengthens the evidence that a mother’s Zika infection during pregnancy raises her baby’s risk of microcephaly and other brain malformations.

The study, published March 3 in the CDC’s Morbidity and Mortality Weekly Report, examined data collected through birth defect surveillance programs in Massachusetts; North Carolina; and Atlanta, Georgia, in 2013 and 2014. In that timeframe — before Zika appeared in the United States — microcephaly, brain abnormalities or another Zika-associated birth defect appeared in just 3 out of every 1,000 live births.

But from January to September 2016, 26 babies out of 442 born to mothers with suspected Zika virus infection during pregnancy showed these defects, according to data from the U.S. Zika Pregnancy Registry. That’s an incidence of nearly 60 per 1,000 pregnancies carried by women with Zika, far higher than the pre-Zika level.

Though the two datasets were collected using different measures and so aren’t directly comparable, the findings bolster previous evidence suggesting that certain brain defects appear much more frequently in babies born to Zika-infected mothers.

Saturn serves up the closest thing to space pasta, the latest round of images from NASA’s Cassini probe, released March 9, show.

On March 7, the spacecraft snapped a series of portraits of Pan, Saturn’s small moon that orbits within a 325-kilometer gap in one of the planet’s rings. Taken at a distance of 24,572 kilometers from the moon, these are the closest images of Pan to date.

The close-ups could help refine astronomers’ understanding of the mini moon’s geology and shape. Pan has a distinctive ridge along its equator, which in the past has prompted astronomers to liken the moon’s shape to that of a flying saucer. In the new images, Pan’s ridge isn’t uniform like that of a fictional alien spacecraft. Instead, it’s uneven, creating an overall shape that more closely resembles a ravioli or wrinkly walnut.

Still, the ridge’s distinctness is “what is so spectacular and eye-opening in these images,” says imaging team leader Carolyn Porco of the Space Science Institute in Boulder, Colo. That supports the theory that the ridge is made of material from Saturn’s rings that continued to rain down on Pan’s equator after it formed.

Cassini captured the images on one of a series of ring-grazing orbits, as part of its final few months orbiting Saturn. Though it won’t get this close to Pan again, the probe is scheduled to swing past Saturn’s other “flying saucer” moon, Atlas, on April 12.

Physicists have snagged a bounty of five new particles in one go.

Members of the LHCb experiment, located at the Large Hadron Collider near Geneva, reported the prolific particle procurement in a paper posted online March 14 at arXiv.org. The five particles are each composed of three quarks — a class of particle that makes up larger particles such as protons and neutrons. Each of the new particles comprises two “strange” quarks and one “charm” quark.

The five particles are in various excited, or high-energy, states — giving each particle a different mass and a different arrangement of quarks within. Such particles are expected to exist according to the theory of the strong nuclear force, which bundles quarks together into larger particles.

The five excited particles are named after their low-energy relative, Ωc0 or omega-c-zero. Their rather uninspiring monikers are Ωc(3000)0, Ωc(3050) 0, Ωc(3066) 0, Ωc(3090) 0 and Ωc(3119) 0. Each number in parentheses indicates the mass of the particle in millions of electron volts.

Nomadic warriors and herders known as the Huns are described in historical accounts as having instigated the fifth century fall of the Roman Empire under Attila’s leadership. But the invaders weren’t always so fierce. Sometimes they shared rather than fought with the Romans, new evidence suggests.

Huns and farmers living around the Roman Empire’s eastern border, where the Danube River runs through present-day Hungary, borrowed ways of life from each other during the fifth century, say archaeologist Susanne Hakenbeck of the University of Cambridge and colleagues. Nomadic Huns on the Roman frontier raised relatively small numbers of animals and grew some crops, while border-zone farmers incorporated more meat into what had been a wheat- and vegetable-heavy diet, the scientists report March 22 in PLOS ONE.
“Our data show that the dietary strategies of the people on both sides of the Roman frontier were not fundamentally different,” Hakenbeck says.

Their findings challenge a traditional view of the Huns as marauders who roamed hundreds of kilometers from Central Asia to Europe. There’s no evidence of major social upheavals or a geographically distinctive group of newcomers at the frontier sites, so at least some Huns may have been homegrown, Hakenbeck suggests. Rapidly forming groups of Hun warriors and herders on horseback could have emerged in southeastern Europe not far from the Roman Empire’s border, perhaps supplemented by nomadic newcomers from farther east near the Black Sea, she proposes.

Still, geographic origins of the Huns are tough to pin down, says archaeologist Ursula Brosseder of the University of Bonn in Germany. The Huns developed as a political movement that picked up members from various ethnic groups as it spread, she explains. Brosseder suspects the “Hun phenomenon” formed on the grasslands of Western Eurasia, a territory that includes regions cited by Hakenbeck. The earliest evidence of Huns in that region dates to about 2,400 years ago.
The new study supports the idea that herding communities adapted flexibly to new environments, sometimes relying only on their livestock and at other times farming to varying extents, Brosseder says. Nomadic herders in Asia probably cultivated millet, a fast-growing cereal that can be used to feed people and horses, Hakenbeck says.
Her group studied skeletons of 234 people buried at five previously excavated sites on or near the Roman frontier. Each site contained evidence of contact with Huns, including bronze artifacts and adult skulls with elongated braincases created by binding the head during childhood. Reasons for this practice are poorly understood. It may have signified affiliation with the Huns or social status of some kind.

Graves at a Roman fort and a nearby cemetery lay on Roman land, about 150 kilometers from the frontier. Another two cemeteries were situated on the banks of the Danube River, directly on the Roman frontier. A final graveyard fell outside Roman territory. It was located about 150 kilometers east of the border.

Measurements of ratios of specific forms of carbon, nitrogen and oxygen in teeth and ribs enabled the scientists to identify what types of plants and how much meat or milk individuals ate during childhood, early adulthood and toward the end of their lives.

Results pointed to considerable consumption of cultivated plants, most likely millet, as well as meat or milk at all five sites. Variations on this general pattern occurred across sites and among individuals at each site, suggesting that groups and individuals rapidly adjusted how much they farmed or herded as circumstances dictated. “This mixing and matching was likely a kind of economic insurance policy in violent and unstable times,” Hakenbeck says.

Hakenbeck’s group also measured another tooth element, strontium, to determine whether individuals at four of the sites had grown up drinking water and eating food in the locales where they were buried. Between 30 and 50 percent of individuals studied at those sites weren’t locals, and the birthplaces of these people remain a mystery, Hakenbeck says.

In many cases, both newcomers and natives to the Roman frontier substantially changed their eating habits over the course of their lives, the researchers find. That fits Hakenbeck’s “mix and match” scenario, in which a fluctuating diet aided survival on the empire’s edge.