Global emissions of carbon dioxide won’t increase much in 2016 despite overall economic growth, newly released bookkeeping suggests. The result marks a three-year-long plateau in the amount of CO2 released by human activities, scientists from the Global Carbon Project report November 14 in Earth System Science Data.

The group’s projected rise in CO2 emissions of 0.2 percent for 2016 is far lower than the rapid emissions growth of around 2.3 percent annually on average from 2004 through 2013. Emissions increased by about 0.7 percent in 2014 over the previous year and remained largely flat in 2015.

China is largely responsible for the emissions slowdown, the researchers write. The country is the world’s largest carbon dioxide emitter and is projected to reduce its CO2 emissions by 0.5 percent this year.

SAN ANTONIO — A roughly 3,000-year-old cemetery on Israel’s coast is providing an unprecedented look at burial practices of the Philistines, a mysterious population known from the Old Testament for having battled the Israelites.

Work at the Ashkelon cemetery from 2013 to 2016 has uncovered remains of at least 227 individuals, ranging from infants to older adults. Only a small section of the cemetery has been explored. Archaeologist and excavation director Adam Aja of the Harvard Semitic Museum estimates that approximately 1,200 people were interred there over a span of about 100 years.
“For the first time, we have found a formal Philistine cemetery,” Aja said November 18 at the annual meeting of the American Schools of Oriental Research. Aja and his colleagues first announced having found the Philistine graveyard on July 10. He was among several researchers to present their latest findings about the cemetery at the meeting.

Despite the new discoveries, the geographic origins of the Philistines remain unknown, Aja said. It’s also unclear how early Philistines reached the Middle East or how much their culture changed by the time they started burying their dead at Ashkelon.

Philistine burial practices have been discussed and debated for about a century. Other ancient Philistine sites in Israel, also identified in ancient texts, have yielded individual graves and small-scale burial grounds.

At Ashkelon, the dead were interred in several ways. Most individuals were placed in shallow pits, often with pairs of jugs or storage containers near the bodies. Some pits contained a person’s remains that had been buried on top of one or more previously interred bodies. Bronze earrings, bracelets, rings and other jewelry adorn most skeletons of children and women. Several pit graves of male skeletons include ornamental beads or engraved stones.

One grave holds a set of iron arrows near a man’s hip. A quiver probably once held the arrows at the man’s side, Aja suggested.
Researchers also uncovered ashes and bone fragments from six human cremations in sealed jars placed in pit graves.

At least eight stone burial chambers capped with stone slabs were also found. The largest chamber held skeletons of 23 individuals. These burial chambers were aligned in three rows that ran parallel to the coast, Aja said.

Tapered storage jars found in pit graves and burial chambers were influenced by pottery of the Canaanites, a nearby population along the Mediterranean coast, said team member Janling Fu of Harvard University.

Fu suspects the excavation is located at the cemetery’s edge. Considerable space between some burials suggests denser clusters of grave sites lie nearby, he proposed, raising the prospect of learning much more about how the Philistines treated their dead.

Although the excavation is in its early stages, it’s clear that Philistines buried at Ashkelon show signs of physiological stress, reported bioarchaeologist and team member Sherry Fox of Eastern Michigan University in Ypsilanti. Many individuals’ teeth have signs of growth interruptions caused by fever, malnutrition or a range of possible biological disorders, she said.

Relatively short average heights for people buried at Ashkelon — about 5 feet, 1 inch for men and 4 feet, 10 inches for women — also fit a scenario of biological stress, Fox said. Short stature and minimal height differences between men and women occur with population-wide stresses such as malnutrition, she said.

The Philistines were a famously combative crowd. Archaeologist Eric Meyers of Duke University, who was not a member of the Ashkelon team, wondered if at least some of those buried at Ashkelon had been killed in battles or fights. But no head injuries or other skeletal signs of violent encounters appeared among the dead at Ashkelon, Fox said. Neither did any skeletons contain evidence of tumors or cancers.

If DNA can be extracted from the Ashkelon skeletons, scientists may get a glimpse of where the Philistines originally came from. Evolutionary geneticist Johannes Krause of the Max Planck Institute for the Science of Human History in Jena, Germany, is currently directing efforts to retrieve genetic sequences from the Ashkelon bones.

“Our work has only just begun,” Aja said.

The first normally solitary spider to win Dad of the Year sets up housekeeping in a web above his offspring and often ends up as their sole defender and single parent.

Moms handle most parental care known in spiders, says Rafael Rios Moura at the Federal University of Uberlândia in Brazil. But either or both parents care for egg sacs and spiderlings in the small Manogea porracea species he and colleagues studied in a eucalyptus plantation. The dad builds a dome-shaped web above the mom’s web, and either parent will fight hungry invaders looking for baby-spider lunch. In webs with no parents, only about four spiderlings survived per egg sac. But with dad, mom or both on duty, survival more than doubled, the researchers report in the January 2017 Animal Behaviour.
“To the best of my knowledge, there really aren’t other examples where male spiders step up to care for young or eggs,” says Linda Rayor of Cornell University, who has studied spider maternal care. In a group-living Stegodyphus species, some of the males in a communal web will attack intruders, but Manogea dads do much more. They switch from solitary life to a dad-web upstairs, brush rainwater off egg sacs and share defense, sometimes at the cost of their own lives.
Many male web-building spiders stop feeding as adults because they’re out searching for mates instead of catching food with their web, Moura says. Manogea males, however, stick with a female they mated with and build a new food-catching web. Now Moura would like to know whether such commitment makes males unusually choosy about females, he says.

To predators, females “must be very delicious,” Moura says. In the wild he found that many females disappeared, probably eaten, by the end of the breeding season, leaving dads as the sole protector for 68 percent of the egg sacs.

That high female mortality could have been important for evolution of the dads’ care-taking, says behavioral ecologist Eric Yip of Penn State. Just why this species has such high female mortality puzzles him, though. Females, geared up for egg-laying, have rich nutrient stores. Yet, he says, “that’s generally true for all spiders — that females are going to be more nutritious and males are going to be mostly legs.”

A seahorse’s genetic instruction book is giving biologists a few insights into the creature’s odd physical features and rare parenting style.

Researchers decoded a male tiger tail seahorse’s (Hippocampus comes) genome and compared it to the genomes of other seahorses and ray-finned fishes. The analysis revealed a bevy of missing genes and other genetic elements responsible for enamel and fin formation. The absence of these genes may explain their tubelike snouts, small toothless mouths, armored bodies and flexible square tails, the team reports online December 14 in Nature.

Although H. comes may be short a few genes, the seahorse has a surplus of other genes important for male pregnancy — a trait unique to seahorses, sea dragons and pipefish. These genetic differences suggest the tiger tail seahorse has evolved more quickly than its relatives, the researchers conclude.

Famous footprints of nearly 3.7-million-year-old hominids, found in 1976 at Tanzania’s Laetoli site, now have sizable new neighbors.

While excavating small pits in 2015 to evaluate the impact of a proposed field museum at Laetoli, researchers uncovered comparably ancient hominid footprints about 150 meters from the original discoveries. The new finds reveal a vast range of body sizes for ancient members of the human evolutionary family, reports an international team led by archaeologists Fidelis Masao and Elgidius Ichumbaki, both of the University of Dar es Salaam in Tanzania.
A description of the new Laetoli footprints appears online December 14 in eLife.

Scientists exposed 14 hominid footprints, made by two individuals as they walked across wet volcanic ash. More than 500 footprints of ancient horses, rhinos, birds and other animals dotted the area around the hominid tracks. Like previously unearthed tracks of three individuals who apparently strode across the same layer of soft ash at the same time, the latest footprints were probably made by members of Australopithecus afarensis, the team says. Best known for Lucy, a partial skeleton discovered in Ethiopia in 1974, A. afarensis inhabited East Africa from around 4 million to 3 million years ago.

All but one of the 14 hominid impressions come from the same individual. Based on footprint dimensions, the researchers estimate that this presumed adult male — nicknamed Chewie in honor of the outsized Star Wars character Chewbacca — stood about 5 feet 5 inches tall and weighed nearly 100 pounds. That makes him the tallest known A. afarensis. The team calculates that the remaining hominid footprint was probably made by a 4-foot-9-inch female who weighed roughly 87 pounds. Stature estimates based on the other three Laetoli footprint tracks fall below that of the ancient female.

Lucy lived later than the Laetoli crowd, around 3.2 million years ago, and was about 3 ½ feet tall.
If Laetoli’s five impression-makers were traveling together, “we can suppose that the Laetoli social group was similar to that of modern gorillas, with one large male and a harem of smaller females and perhaps juveniles,” says paleontologist and study coauthor Marco Cherin of the University of Perugia in Italy.

Chewie’s stature challenges a popular assumption that hominid body sizes abruptly increased with the emergence of the Homo genus, probably shortly after A. afarensis died out, Cherin adds.

The new paper presents reasonable stature estimates based on the Laetoli footprints, but “we don’t have a firm idea of how foot size was related to overall body size in Australopithecus,” says evolutionary biologist Kevin Hatala of Chatham University in Pittsburgh. Masao’s group referred to size data from present-day humans to calculate heights and weights of A. afarensis footprint-makers. That approach “could lead to some error,” Hatala says.

Stature estimates based on footprints face other obstacles, says paleoanthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History. For instance, some tall individuals have small feet and short folks occasionally have long feet. It’s also unclear whether the new footprints and those from 1976 represent a single group, or if some smaller footprints were also made by males, Haile-Selassie adds. Cherin’s proposal that large A. afarensis males controlled female harems “is a bit of a stretch,” Haile-Selassie says.

The new report doesn’t document surprisingly large size differences among members of Lucy’s kind, Haile-Selassie adds. A. afarensis fossils previously excavated in Ethiopia include a partial male skeleton now estimated by Haile-Selassie and his colleagues to have been only about three inches shorter than Chewie’s reported height (SN: 7/17/10, p. 5).

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.