Climate change flaunted its deadly side during the 2003 European heat wave, which killed over 70,000 people across the continent. In London and Paris alone, global warming led to 570 more heat-related deaths than would be expected without human-caused warming, researchers estimate in the July Environmental Research Letters.
Daniel Mitchell of the University of Oxford and colleagues ran thousands of climate simulations with and without the influence of greenhouse gases emitted by humans. The simulations showed that 70 percent of heat-related deaths in central Paris during the heat wave and 20 percent in Greater London could be attributed to climate change. The study is the first to quantify climate change’s role in the event and will inform policy makers on the risks climate change poses, the researchers say.
A barrage of rocks hitting the solar system 3.9 billion years ago could have dramatically reshaped Earth’s geology and atmosphere. But some of the evidence for this proposed bombardment might be shakier than previously believed, new research suggests. Simplifications made when dating moon rocks could make it appear that asteroid and comet impacts spiked around this time even if the collision rate was actually decreasing, scientists report the week of September 12 in the Proceedings of the National Academy of Sciences.
Many scientists think that a period of relative calm after Earth formed 4.6 billion years ago was interrupted by a period called the Late Heavy Bombardment, when rocky debris pummeled Earth and the other planets. The moon’s cratered surface holds the best evidence for this event; scientists have measured radioactive decay of argon gas trapped inside moon rocks to date when craters on the moon were formed. Many of the hundreds of moon rocks analyzed appear to be around 3.9 billion years old. That suggests the number of rocks hitting the moon suddenly spiked at that time — evidence for a Late Heavy Bombardment.
Geochemists Patrick Boehnke and Mark Harrison of UCLA took a second look at the data. Measuring argon from the same rock at different temperatures leeches the gas from different parts of the rock’s crystals; if all those age values align, researchers can be relatively confident they’re getting an accurate age. But many of the lunar samples previously analyzed gave different ages depending on the temperature at which their argon content was measured.
Instead of colliding sharply once and sitting undisrupted, which might give more uniform age data at different temperatures, these lunar rocks were probably tossed around and slammed into other rocks many times, Boehnke says. So assigning one impact age to those rocks might be an oversimplification.
Boehnke and Harrison created a model to simulate how this simplification might affect the patterns seen when scientists looked at the ages of many rocks. The team modeled 1,000 rocks and assigned each one an impact age. Some rocks hadn’t been knocked around and had a clear impact age. Others had been smashed repeatedly, which changed their argon content and obscured the actual impact age assigned by the model.
The model assumed that asteroid collisions decreased over time — that more of the rocks were older and fewer were newer. But still, collision ages appeared to spike 3.9 billion years ago thanks to the fuzziness introduced by the disrupted rocks. So the apparent asteroid increase at that time might just be a quirk due to the way the argon dating data were compiled and analyzed, not an indication of something dramatic actually happening. “We can’t say the Late Heavy Bombardment didn’t happen,” Boehnke says. Nor do the results invalidate the technique of argon dating, which is used widely by geologists. Instead, Boehnke says, it points to the need for more nuanced interpretation of lunar rock data.
“A lot of data that shows this complexity is being interpreted in a very simplistic way,” he says.
Planetary scientist Simone Marchi says he finds the paper “certainly convincing in saying that we have to be very careful” when interpreting argon dating data from lunar samples.
But there’s other evidence for a Late Heavy Bombardment that doesn’t rely on argon dating, such as dating from more stable radioactive elements and analysis of overlapping craters on the moon, says Marchi, of the Southwest Research Institute in Boulder, Colo. He supports the idea of a gentler Late Heavy Bombardment 4.1 billion years ago, instead of a dramatic burst 3.9 billion years ago (SN: 8/23/14, p.13).
Other recent work has also pointed out limitations in argon dating, says Noah Petro, a planetary geologist at NASA Goddard Space Flight Center in Greenbelt, Md., who wasn’t part of the study. Collecting new samples and analyzing old ones with newer techniques could help scientists update their view of the early solar system. “We’re at this point with the moon right now where we’re finding the limitations of what we think we know.”
Mars is about to get another visitor. The European Space Agency’s ExoMars mission arrives at the Red Planet on October 19. A spacecraft known as the Trace Gas Orbiter will go into orbit around Mars while a lander named Schiaparelli will touch down on the surface.
ESA will live stream the landing starting at 9 a.m. EDT on October 19.
The arrival ends a roughly seven-month journey. Schiaparelli, which separated from the orbiter on October 16, is expected to enter the Martian atmosphere at 10:42 a.m. and land in a plain dubbed Meridiani Planum about six minutes later. Parachutes will ease its entry and rockets will slow the lander down until it is about two meters from the ground, at which point it will drop the rest of the way, cushioned by a collapsible structure.
Schiaparelli will test technology needed for a future European Mars rover. The lander doesn’t have a long-term power source, so it will last for only a few Martian days. But it is carrying a few scientific instruments, such as a camera and weather sensors.
The orbiter will stick around to study trace gases such as methane in the Martian atmosphere. It will eventually become a communication hub between Earth and another European Mars rover expected to arrive in 2021.
There are many places in the world where you can see bottlenose dolphins, but the dolphins swimming in the Port River estuary near Adelaide, Australia, are special. They gambol about in waters surrounded by factories, power stations and other signs of human habitation.
For much of the 20th century, there were no dolphin sightings in the inner estuary. Prior to European settlement in 1858, bottlenose dolphins were commonly seen by the local Kaurna aboriginal tribal group. But as the city of Adelaide was built, the dolphins disappeared. What changed that enabled their return? A combination of improved environmental conditions, a little bit of protection and some public education, researchers report October 24 in Marine Mammal Science.
“The future of these dolphins would appear to be as secure as any population of any species can be in this era of climate change,” says the study’s lead author, Mike Bossley of Whale and Dolphin Conservation Australasia in Port Adelaide, who has studied the area’s dolphins for 25 years.
As the city of Adelaide grew, the Port River grew to be an unfriendly spot for marine wildlife. People cleared away the marshes and mangroves, replacing them with sulfuric acid and soda ash producers, sugar refineries and power stations. Sewage and storm water flowed into the river. Boats and ships traversed the estuary, which had become the main shipping port for the state of South Australia. And no one reported a dolphin sighting between 1940 and 1980.
Scientists began field studies in 1989 and started finding bottlenose dolphins — and documenting threats to them. In addition to pollution, any dolphins brave enough to traverse the Port River had to deal with boat strikes, infections, entanglement with nets and other marine trash and even deliberate attacks. In response, the Adelaide Dolphin Sanctuary was established by law in 2005, setting aside a small patch of river for the resident dolphin population (about 30 live in the river; another 300 visit the area regularly) and establishing resources for public education about the dolphins. And over the last few decades, water quality has improved as some of the least environmentally friendly activities — such as sulfuric acid production, salt evaporation and coal-fired power production — have ended.
In 1990, Bossley and his colleagues started surveying the Port River dolphins. The researchers would take their boat out on a 40-kilometer journey through the estuary, following the same path each time and photographing any dolphins they saw. They used distinguishing marks, such as shape or notches, on a dolphin’s dorsal fin to identify the animal and ensure each was only counted once.
From January 1990 to December 2013, the researchers made a total of 735 complete journeys, averaging one survey every 11.7 days. Based on those surveys, and the near absence of dolphins in the 1980s, the team estimates that bottlenose dolphin sightings are increasing by about 6 percent a year. “The trends in sightings provide compelling evidence of a large change in some aspect of relative abundance and occupancy and usage of the Port River estuary,” the researchers write. The increase could be the result of an increase in the resident population, in the number of visiting dolphins or a combination of both.
Improved water quality may be better for the dolphins or their prey. Plus, the establishment of the sanctuary gave the dolphins some protection against human activities. In addition, Bossley notes, “by designating the area as a sanctuary, the public is both more aware and more protective of the dolphins.” The dolphins still have to deal with human impacts — the river is not pollution free, an attack occurred as recently as 2014 and there’s a growing new potential threat in the form of tourism — but the dolphins appear to be able to cope.
The Adelaide dolphins offer a lesson in conservation, Bossley and his colleagues note. Corralling off large areas for wildlife from human activities isn’t always necessary. “People have to learn to live with wildlife,” Bossley says. And that “requires taking into account both the wildlife itself and its habitats.”
Clusters of a toxic bacterial protein have a surprising structure, differing from similar clumps associated with Alzheimer’s and Parkinson’s in humans, scientists report in the Feb. 24 Science.
These clusters, called amyloids, are defined in part by their structure: straight regions of protein chains called beta strands, folded accordion-style into flat beta sheets, which then stack up to form a fiber. That definition might now need to be broadened.
“All the amyloids that have been structurally looked at so far have certain characteristics,” says Matthew Chapman, a biologist at the University of Michigan in Ann Arbor who wasn’t part of the work. “This is the odd amyloid out right now.” In the human brain, misfolded proteins can form amyloids that trigger neurodegenerative diseases. But amyloids aren’t always a sign of something gone wrong — some bacteria make amyloids to help defend their turf.
In Staphylococcus aureus, for example, the PSMα3 protein assembles into amyloids that help the bacteria kill other cells. Previous research suggested that PSMα3 clusters were like any other amyloid. But researchers using X-ray crystallography found that instead of straight beta strands, the PSMα3 fiber was made up of curly structures called alpha helices that resemble an old-fashioned phone cord. The helices still formed a familiar fiber shape just like the beta strands did, but the sheets making up that fiber were rippled instead of flat. “From the outside, it looks exactly the same. But zooming in, it looks completely different in its fundamental units,” says study coauthor Meytal Landau, a biologist at the Technion–Israel Institute of Technology in Haifa. “It’s something that really threw me off.”
Chapman first thought the finding must have been a mistake. Alpha helices are a very common protein structure, but “they don’t typically stack on each other to form a sheet,” he says. “That’s a really rare structure in nature.” Now, he says, it’s quite clear that alpha helices are building this amyloid.
Getting such a detailed picture of an amyloid is a challenge, so Landau isn’t sure whether PSMα3 is truly an exception or whether other proteins can make similar amyloid-like clusters.
Either way, knowing the structure can be useful. When Landau and her colleagues prevented the PSMα3 from forming an amyloid-like structure, the bacteria weren’t as good at attacking human immune cells. Rather than hunting for strong drugs that target the hard-to-kill bacteria themselves, Landau suggests, scientists might eventually be able to develop drugs that target the proteins controlling the bacteria’s aggression.
Blame oxidation for rusted bridges and browned avocados. But this fundamental process can be harnessed for good, too — and now scientists have scored front-row seats that could show them how.
Researchers watched at near-atomic resolution as iron nanoparticles transformed into iron oxide — not rust in this case, but related compounds. That closeup view could help scientists better control oxidation and design corrosion-resistant materials or new kinds of catalysts, the researchers report in the April 21 Science. This is the first time the oxidation process has been observed in such detail, says Andreu Cabot, a physicist at the Catalonia Institute for Energy Research in Barcelona who wasn’t part of the study.
When a metal oxidizes, its atoms mix and mingle with oxygen atoms to create a new material. That process is perhaps most famous for creating rust, which flakes and corrodes. But iron can oxidize in a variety of ways, some of which are useful.
For instance, chemist Yugang Sun and his colleagues at Temple University in Philadelphia are trying to create hollow iron oxide nanoparticles that could serve as catalysts to speed up chemical reactions or as vessels to deliver drugs or store energy in chemical form. But making these “nanoshells” from iron nanoparticles requires precise control over the oxidation process.
If oxygen atoms work their way into an iron nanoparticle faster than the iron atoms can diffuse out, that nanoparticle becomes a tight, solid ball, Sun says. If the iron diffuses out faster than the oxygen comes in, on the other hand, it becomes the hollow sphere that Sun’s lab wants.
Controlling that process is difficult because it has been unclear exactly how these shells form on an atomic level, Sun says. Scientists haven’t been able to watch it happen, because high-powered microscopy techniques can disrupt the reaction or show the action in only two dimensions. Sun’s team tried a different approach to observe the reaction, by shooting X-rays at many identical iron nanoparticles suspended in a liquid. Each time the X-rays hit a different material — moving from the liquid to the solid, for instance — they scattered. By tracking how the X-rays bounced off many small, uniform iron nanoparticles, the researchers were able to reconstruct where individual atoms were going as the particles oxidized into hollow shells over the course of several hours.
The researchers watched as the iron moved out of the center of the nanoparticle to react with the oxygen, initially forming many small holes inside the nanoparticle. Eventually, those empty spaces merged together to form one big void in the middle of the nanoparticle.
“The impact of this paper is more than just the hollow [nanoparticles],” says Yadong Yin, a chemist at the University of California, Riverside who wasn’t involved in the research. The imaging technique itself will be a useful way to study how other types of nanoparticles form — something scientists still don’t understand well, he says. It can be used to gain insight into other types of oxidation, too.
Chaco Canyon is a land of extremes. Summer heat scorches the desert canyon, which is sandwiched between sandstone cliffs nearly two kilometers above sea level in New Mexico’s northwestern corner. Bitter cold sweeps in for winter. Temperatures can swing as many as 28 degrees Celsius during the course of a day. Through it all, Chaco Canyon maintains a desolate beauty and a craggy pride as home to one of ancient America’s most enigmatic civilizations.
Scientists have struggled to understand Chaco society since its first excavations in the late 1800s. Who first settled Chaco Canyon around 1,200 years ago is still a mystery. Many researchers suspect that it took a few hundred years for a fledgling city-state run by an elite social class to emerge. Political and cultural ties between the ancient society and Chaco-style communities outside the canyon also perplex. Then there’s the puzzle of how people survived from about 800 to around 1300 on the rough, parched terrain. A new generation of Chaco studies and discoveries is under way, partly thanks to a young researcher’s skeleton reassembly project. This jigsaw job required a lot of travel, but not to Chaco Canyon.
That’s because bones of people excavated at Chaco in the 1890s and 1920s were packed away in boxes and drawers at museums in New York City, Chicago and Washington, D.C. Kerriann Marden visited all of these places to retrieve far-flung body parts from one site in particular — Pueblo Bonito, the oldest and largest of a dozen huge stone great houses in Chaco Canyon. The structure was built, along with a range of smaller structures, between about 800 and 1130. Pueblo Bonito was massive, rising at least five stories with around 650 rooms. It has yielded more human bones and artifacts than any other Chaco site. Research has focused on this great house presumably reserved for Chaco’s elite families; the lives of workaday folk have been largely unexplored, even in the latest studies. During Chaco society’s heyday, other civilizations peaked elsewhere in the Americas, including the Maya in Central America. Just as present-day Maya groups trace their ancestry back to that ancient civilization, today’s Pueblo tribes, such as the Hopi and Zuni, consider Chaco people to have been their forebears. Navajo Nation also claims an ancestral tie to Chaco society. Reassembly required Archaeological excavations a century or more ago — at Pueblo Bonito and elsewhere — didn’t follow today’s rigorous standards for excavating and preserving remains. The work consisted of little more than mining for bones and artifacts, then carting the discoveries off to museums. As an anthropology graduate student at Tulane University in New Orleans, Marden journeyed back and forth between New York’s American Museum of Natural History, Chicago’s Field Museum and Washington’s Smithsonian National Museum of Natural History from 2005 to 2011. She painstakingly reunited long-dead Chaco individuals’ skulls with arms, legs with feet and so on. Marden is now a forensic anthropologist at Eastern New Mexico University in Portales.
As skeletons assumed their former shapes, a couple of peculiar things stood out. First, many individuals bore signs of disease, including tuberculosis and syphilis. That seemed peculiar for people who were buried in a great house typically thought to have been reserved primarily for society’s upper crust, not for the ill. Second, bodies had been manipulated in unusual ways and for unknown reasons. Comparisons of restored skeletons with field notes and photographs from original excavations indicated, for instance, that one woman was originally found with a fetus’s fragile remains in her pelvic cavity and her own bones below the knees missing. Her body lay across a room from several intact bodies.
“Nothing is simple at Pueblo Bonito,” Marden says. Her campaign to put Pueblo Bonito skeletons back together has enabled a couple of provocative new investigations. One concludes that members of a single maternal line wielded power in Chaco society from the start through an unexpected stretch of at least 330 years and perhaps 10 generations. Another study proposes that Chaco society’s founders were not outsiders with experience constructing huge buildings, as many researchers have assumed. People living in and near Chaco Canyon may have established a cliff-bordered society all on their own. Other new findings suggest that Chaco residents contacted and traded with people living as far as 2,500 kilometers to the south in Central America and as close as 75 kilometers to the west and south. It’s debatable, though, whether Chaco Canyon’s 2,000 to 3,000 residents could raise enough crops to feed themselves or whether they had to trade for staples such as maize.
Less contentious — but far weirder — is evidence from graves and artwork that Chaco people revered community members with six toes and often created images of human feet and footprints with and without extra digits.
DNA dynasty Fittingly, Chaco society’s archaeological footprint covers what was once an extensive regional system of buildings and roads. The largest great houses were clustered in a 2-kilometer-diameter downtown zone at the center of Chaco Canyon. Smaller great houses, ritual structures called kivas, groups of small family houses and other urban features, connected by a network of straight dirt roads, fanned out from the canyon across an area the size of Ireland.
After Chaco society dissolved around 1300, Pueblo groups may have rejected its centralized political system and social classes, says archaeologist Stephen Lekson of the University of Colorado Boulder. Pueblo people today live in small communities oriented around clans based on maternal lines of descent.
Therein lies a connection between past and present, says archaeologist Stephen Plog of the University of Virginia in Charlottesville. Many individuals buried in one of Pueblo Bonito’s oldest rooms, known to researchers as Room 33, shared maternal ancestry (SN Online: 2/21/17). Plog and colleagues — led by Penn State archaeologist Douglas Kennett — extracted mitochondrial DNA, which is typically passed from mother to child, from skeletons of nine of 14 individuals interred in Room 33. Marden’s reassembly project was crucial to identifying individuals whose DNA was analyzed.
Members of this Pueblo Bonito group, the researchers reported February 21 in Nature Communications, inherited mitochondrial DNA that was similar enough to signal shared kinship with a female line. Nuclear DNA recovered from six Room 33 skeletons identified two as mother and daughter and two others as a grandmother and grandson. Children inherit nuclear DNA from both parents. Room 33 is a crypt with a complex history. Two men were buried beneath the chamber’s wooden floor, one below the other. The lowermost body had a gash in the head. Plog suspects the man was bashed on the noggin during a fight. Marden thinks it’s more likely that someone with a shovel, perhaps a looter, broke the skull after the man had been buried.
Thousands of offerings, including turquoise and shell beads and pendants, were heaped around the two bodies under Room 33’s floor, with the lion’s share surrounding the bottommost man. Chaco people laid a wooden plank floor over the two men’s graves before additional bodies were buried in the chamber.
Radiocarbon dating conducted by Plog’s group gives a rough timeline for Room 33’s burials. The first two men were placed there as early as 800. Construction of the wooden floor occurred by about 900. Additional burials took place intermittently up to 1130, the new dating indicates. Activity in Room 33 occurred as civilizations flourished throughout the Americas, from what’s now the U.S. Midwest to Central and South America.
Plog regards the extravagantly buried man at the base of Room 33 as an early leader from a prominent Chaco family dynasty. Based on the exceptional treatment given to all deceased individuals placed in the special room in Chaco’s first and largest great house, Plog suspects these folks belonged to a maternal line in which leadership was handed down from the ninth to the 12th century. At that point, researchers suspect, many Chaco residents and possibly members of nearby communities moved to a settlement 50 kilometers north of Chaco Canyon. A Chaco-style great house there was occupied from 1140 to the 1290s, consistent with an influx of people familiar with Chaco architecture.
“Our findings reinforce the possibility that a complex society existed in Chaco by the ninth century, about 200 years earlier than has often been assumed,” Plog says. If so, Chaco society consisted of a few powerful families and lots of commoners from the start.
Local founders That’s not the only surprise encased in Pueblo Bonito’s skeletal trove. Chemical analyses of teeth from 61 individuals interred in two sections of the great house indicate that most of these people grew up eating food and drinking water from Chaco Canyon or nearby areas to the south. These results challenge an influential idea established over the last decade that people from ancient settlements that included large structures, located more than 160 kilometers north of Chaco Canyon, migrated south and brought with them knowledge of how to design great houses.
Archaeologist T. Douglas Price of the University of Wisconsin–Madison, Plog and colleagues made a case for local origins of Chaco society in the February issue of the Journal of Archaeological Science: Reports.
The researchers focused on the two sections of Pueblo Bonito where human skeletons were found in previous excavations. Room 33 and three adjacent chambers on the great house’s northern side contained burials of about 25 individuals. Four rooms on the structure’s western side produced remains of more than 80 bodies.
Radiocarbon analyses of 12 skeletons from the western chambers, led by Marden during her graduate work, dates the bodies to between the years 687 and 949. Further radiocarbon dating is needed to narrow that wide age range for western interments, Marden says.
Ratios of certain forms of chemical elements — strontium, oxygen and lead — suggest that 58 of 61 people buried in Pueblo Bonito had grown up eating plants and animals and drinking water that came from the Chaco Canyon area.
Plog suspects that the few Chaco Canyon outsiders that have been identified at Pueblo Bonito came from somewhere nearby. It’s unclear what roles those outsiders assumed in Chaco society. But finding a majority of locals buried in the great house challenges a previous proposal that Chaco Canyon was first settled by people from the north, Plog says. Design similarities between some northern stone buildings and Chaco great houses fueled that suspicion.
The new DNA and chemical results aren’t entirely consistent. Although the two men placed beneath the floor of Room 33 belonged to a maternal line interred at Pueblo Bonito, the chemical makeup of their bones suggests they might have grown up outside Chaco Canyon. For now, where the men were raised and how they ended up in Pueblo Bonito remains a mystery. “It will take a while to make sense of both datasets,” Plog says. Chaco lot Ancient Chaco society was based in northwestern New Mexico’s Chaco Canyon (green rectangle). Chaco-style great houses (red) appear throughout the region. Roads (some shown here in yellow) radiated out from Chaco Canyon.
Click the dots for more. Sources: Map: T.D. Price et al/J. Archaeol. Sci.: Reports 2017; feet: P. Crown and H. Mattson/Amer. Antiquity 2016; wood: C. Guiterman et al/PNAS 2016; macaws: A. Watson et al/PNAS 2015; Aztec Ruin: H. Mattson/J. Anthro. Archaeo. 2016.
Reign fall Marden says it’s too early to say much of anything about how Chaco society was organized based on initial genetic evidence from Pueblo Bonito skeletons. “Huge pronouncements about Chaco social structure are being made based on partial, flawed data,” she says. “It’s like excavating only human foot bones and concluding that people at that time had no hands.”
DNA from a mere nine folks can’t support a sweeping conclusion that Pueblo Bonito housed the dead of a Chaco maternal dynasty, Marden argues. Additional genetic samples are needed to determine, for instance, whether people buried elsewhere in Pueblo Bonito, in other great houses in and near Chaco Canyon and in smaller Chaco buildings belonged to the same maternal line as those from Room 33, she holds.
DNA studies of more Chaco skeletons are unlikely in the near future. Some Pueblo groups have complained that scientists didn’t consult with them before removing genetic material from the bones of people regarded as ancestors. In a related case, scientists have collaborated with Native Americans in the Pacific Northwest, who provided DNA for comparisons to Kennewick Man’s DNA (SN: 7/25/15, p. 6).
In a written statement, the American Museum of Natural History says it approved the new DNA analysis of Chaco bones from its collection based on discussions with 20 Native American tribes in the U.S. Southwest during the 1990s. No claims of cultural ties to Chaco people were lodged then or since, making the new investigation legal, the museum statement concludes.
A formal inquiry to the museum about its decision will be filed soon, says Leigh Kuwanwisiwma, director of the Hopi Cultural Preservation Office in Kykotsmovi, Ariz.
So for now, DNA from nine Chaco individuals raises only provocative possibilities. The two men interred beneath Room 33’s floor appear to have been important, Marden acknowledges, but that doesn’t make them founding fathers of a Chaco dynasty that traced descent through a female line. Room 33 may simply have housed deceased members of a prominent family. Relatives probably visited the men’s graves in Room 33 on occasion, leaving offerings that piled up over time. Those items, including turquoise frog ornaments and seashells, often refer to water, a precious commodity in Chaco society. However, researchers can easily see signs of symbolic rituals where they don’t exist, Marden warns. For instance, for more than a century, many researchers have assumed that a hole cut into Room 33’s floor represented an entrance to a supernatural underworld for the dead. The floor opening was more likely used as a handle to remove surrounding planks to reach the graves below, she suspects
“There’s undoubtedly symbolism at Pueblo Bonito, but as a forensic anthropologist, I’m looking for practical explanations,” Marden says.
Southern influences What appears clear at Pueblo Bonito is that connections existed between Chaco society and populations extending as far south as Central America.
Recovered pottery tells a similar story to Price’s teeth analysis suggesting local as well as southern origins for Pueblo Bonito’s dead. Vessels recovered at that great house and other Chaco sites resemble pottery from comparably ancient sites about 50 kilometers to the southwest. Anthropological archaeologist Barbara Mills of the University of Arizona in Tucson reported the finding March 30 in Vancouver at the annual meeting of the Society for American Archaeology.
The Zuni Mountains, about 75 kilometers to the south, and the Chuska Mountains, about the same distance to the west of Chaco Canyon, provided close to 70 percent of the more than 240,000 trees that were used for roof beams, doorframes and other features of Chaco great houses. A team led by dendrochronologist Christopher Guiterman at the University of Arizona reported those findings, based on matching tree ring configurations at Chaco and in the two mountain ranges, last year in Proceedings of the National Academy of Sciences.
Chaco people also apparently traded turquoise objects for goods from societies in southern Mexico and Central America. Residue on Pueblo Bonito jars and pitchers comes from a chocolate beverage made from cacao that grows in those tropical areas (SN Online: 3/17/11). Exotic birds — scarlet macaws — from the same region turned up at Pueblo Bonito starting in the late 800s.
Colorado’s Lekson thinks southern influences on Chaco society run deep. Chaco’s social and political structure drew on a type of small city-state in what’s now southern Mexico and Central America called an altepetl, Lekson proposes. An altepetl consisted of seven or eight related noble families, each ruling over commoners who cultivated crops and paid tribute in food and labor. Leading noble families took turns ruling an altepetl and elected a figurehead king.
Chaco’s seven great houses served as elite families’ residences, as in an altepetl, Lekson proposes. Other Chaco structures housed minor nobles, priests and commoners, from this perspective.
That’s a minority view, though. Mills, Plog and several other Chaco researchers suspect that Chaco society was organized around houses of varying social status. A structure’s status would have been based on its age and ritual connections to ancestors. Differences in architecture among great houses suggest that they were ranked as well, Mills says. If that’s how the system worked, heads of various Chaco houses probably led their respective extended families.
“Chaco was a hierarchically organized society from the start,” Plog says.
It helped that Chaco Canyon’s soil, although salty, was able to support widespread maize cultivation with the help of irrigation ditches, Plog and his colleagues, led by University of Cincinnati geoarchaeologist Kenneth Tankersley, reported in the October 2016 Journal of Archaeological Science: Reports.
University of Colorado hydrologist and geochemist Larry Benson says that’s unlikely. Chaco Canyon soil was too salty and annual rainfall too low to feed more than a few hundred people, Benson reported online last December in the same journal. He suspects that the Chaco crowd imported maize grown near the Chuska Mountains.
Special feet Chaco society’s puzzles go beyond who was in charge and where meals came from. One of the ancient population’s most vexing oddities concerns feet. Six-toed individuals appear to have held special status at Pueblo Bonito, says archaeologist Patricia Crown of the University of New Mexico in Albuquerque. “Having six toes brought social honor in Chaco society,” Crown holds. “We don’t know why Chaco people were so interested in feet or what feet symbolized to them.” A review of Pueblo Bonito skeletons and artifacts conducted by Crown and her colleagues, published in the July 2016 American Antiquity, identified three six-toed individuals among the burials. Only one case had previously been noticed — the less-decorated man placed beneath Room 33’s floor.
It’s not known how common it was to be born with more than five toes or fingers in the ancient U.S. Southwest. This condition affects about 2.4 of every 1,000 Native Americans today.
Footprints and handprints sporting six digits also appear on several plastered walls at Pueblo Bonito. Rock art in Chaco Canyon depicts almost 800 human feet, with anywhere from three to eight toes.
Of 13 ancient sandals recovered at Pueblo Bonito, seven include woven extensions on the outer border for a sixth toe.
Ancient cultures of Southern Mexico and Central America sometimes depicted their gods with six toes. Chaco folk probably regarded extra-toed peers as special but not divine, Crown says. Of the three six-toed individuals given the presumed honor of a Pueblo Bonito burial, only one lay in an elaborate grave. Such treatment would have applied to all three if an extra toe signified godlike status, she says.
That’s a preliminary conclusion, though. Chaco residents constantly reworked and rebuilt Pueblo Bonito for more than 300 years, so deciphering precisely what happened in the great house’s many rooms and at particular times is daunting.
Pinning down Chaco’s origins is equally challenging, Plog says. Pueblo Bonito and many other Chaco structures were built on soil that accumulated when Chaco Canyon streams occasionally flooded. No one has looked for possible forerunners of the ancient society buried underneath all that earth.
Researchers trying to crack Chaco’s secrets while burdened with so many crucial unknowns can be excused for feeling like the pregnant woman buried inside Pueblo Bonito — cut off at the knees.
The first evidence for an exomoon — a moon orbiting a planet orbiting a distant star — may have been spotted in data from the Kepler space telescope. But surprisingly, exomoons in general may be rare, at least around planets close to their stars.
Alex Teachey and David Kipping of Columbia University analyzed the dips in light from exoplanets passing, or transiting, in front of their stars. A second, smaller dip that appears ahead of or behind the planet could reveal a moon. Such exomoons, researchers have speculated, may be among the best places in the universe to look for extraterrestrial life. But because those signals are faint and inconsistent, they take a lot of computing power to find. Kipping has been searching for such signals for years in a project called the Hunt for Exomoons with Kepler. In a paper posted online July 26 at arXiv.org, Teachey and Kipping present the first evidence for an exomoon candidate: Kepler 1625b i. The team analyzed 284 planets that seemed like good candidates for hosting detectable moons. “Out of those, this object popped out,” Kipping says.
The object, if it exists, orbits a planet slightly larger than Jupiter around a star about 4,000 light-years away. Because the potential moon is probably about the size of Neptune, the team nicknamed it “Neptmoon.” The team plans to check if the moon is really there by using the Hubble Space Telescope to watch for another transit on October 29.
“We threw all of our tests at it, and it passed them,” Kipping says. “But we were still pretty suspicious. We knew the best way to confirm it was to get more data. Hubble is the best telescope for the job.”
If confirmed, this moon would be almost in a class of its own. The team calculated that, statistically speaking, only 38 percent of Jupiter-like planets close to their stars are likely to host moons like Jupiter’s. That’s surprising, but given that there are thousands of exoplanets still to check, more moons may still be out there. The hunt continues.
Zika’s damaging neurological effects might someday be enlisted for good — to treat brain cancer.
In human cells and in mice, the virus infected and killed the stem cells that become a glioblastoma, an aggressive brain tumor, but left healthy brain cells alone. Jeremy Rich, a regenerative medicine scientist at the University of California, San Diego, and colleagues report the findings online September 5 in the Journal of Experimental Medicine.
Previous studies had shown that Zika kills stem cells that generate nerve cells in developing brains (SN: 4/2/16, p. 26). Because of similarities between those neural precursor cells and stem cells that turn into glioblastomas, Rich’s team suspected the virus might also target the cells that cause the notoriously deadly type of cancer. In the United States, about 12,000 people are expected to be diagnosed with glioblastoma in 2017. (It’s the type of cancer U.S. Senator John McCain was found to have in July.) Even with treatment, most patients live only about a year after diagnosis, and tumors frequently recur. In cultures of human cells, Zika infected glioblastoma stem cells and halted their growth, Rich and colleagues report. The virus also infected full-blown glioblastoma cells but at a lower rate, and didn’t infect normal brain tissues. Zika-infected mice with glioblastoma either saw their tumors shrink or their tumor growth slow compared with uninfected mice. The virus-infected mice lived longer, too. In one trial, almost half of the mice survived more than six weeks after being infected with Zika, while all of the uninfected mice died within two weeks of receiving a placebo.
Using a virus to knock out cancer isn’t a completely new idea. Treatments that rely on modified polioviruses to target tumors such as glioblastomas are already in clinical trials in the United States, and there’s a modified herpesvirus approved by the U.S. Food and Drug Administration for treating melanoma.
These cancer-fighting viruses seem to work in two ways, says Andrew Zloza, head of surgical oncology research at the Rutgers Cancer Institute of New Jersey in New Brunswick. First, the viruses infect and kill cancer cells. Then, as those cancer cells split open, previously hidden tumor fragments become visible to the immune system, which can recognize and fight them.
“Right now we don’t know what kind of viruses are best” for fighting cancer, Zloza says — whether it’s more effective to use a common virus that many people have been exposed to or something more unusual. But now, Zika is yet another candidate.
Further testing is needed to determine whether the virus is safe and effective in humans. Since Zika’s effects are more harmful in developing brains, a Zika-based cancer therapy might be safe only in adults. And the virus would need to be genetically modified to make it safer and less transmissible. Rich and colleagues are now testing in mice whether combining Zika with traditional cancer treatments such as chemotherapy is more effective than either treatment by itself. Because Zika targets the cells that generate tumor cells, it might prevent tumors from recurring.
Here’s some heartbreaking news for people pinning their hopes on online matchmaking sites: It’s virtually impossible to forecast a love connection.
Maybe that’s not so shocking to survivors of the dating wars. But now science is weighing in. Extensive background data on two individuals — comparable to that collected by digital dating services — can’t predict whether that pair will romantically click during a four-minute, face-to-face speed date, say psychologist Samantha Joel of the University of Utah in Salt Lake City and colleagues.
People know when an in-person meeting on a speed date has gone smoothly or felt right — and that bodes well for mutual attraction, the investigators report online August 30 in Psychological Science. But on paper, no blend of personal qualities and partner preferences thought to influence mate choices pegged which opposite-sex duos would hit it off, Joel’s group concludes.
Joel expected that, say, a person who reported being attracted to extroverted people would generate the most chemistry with speed daters who reported being extroverted. Or, two people who reported being good-looking and having particularly warm personalities would feel especially attracted to one another after brief dates. But that’s not what Joel and coauthors Paul Eastwick of the University of California, Davis and Eli Finkel of Northwestern University in Evanston, Ill., found. The researchers studied 350 heterosexual college students — almost evenly split between males and females — who participated in one of 15 speed-dating events in 2005 or 2007. Participants filled out either 182-item or 112-item questionnaires about their personality traits and preferences in romantic partners. The students then completed about 12 speed dates. Afterward, participants rated their interest in and sexual attraction to each person they met.
Some qualities romance seekers said they wanted — such as extroversion and warmth — predicted individual speed daters’ greater attractiveness to others in general. But a statistical analysis of participants’ responses found that no traits or preferences, or combinations of traits and preferences, predicted how much one person especially desired another person after a speed date.
Joel’s team has not analyzed evidence from online matchmaking services to see if their questionnaires frequently pair people who generate romantic heat. “But our findings suggest that it’s quite difficult to predict initial romantic attraction using self-report measures before two people have met,” Joel says.
Biological anthropologist Helen Fisher, a senior researcher at Indiana University’s Kinsey Institute in Bloomington, agrees. “You’ve got to meet someone in person to trigger the brain circuitry for romantic love,” Fisher says.
That comes as no surprise to operators of online dating sites, she adds. These sites typically don’t promise customers romantic connections, says Fisher, who is a consultant for online dating site Match.com and founded its affiliated website, Chemistry.com. The aim is to provide an array of potential dates with background and personality traits requested by a customer. The rest is up to those who decide to go on dates.
