This class of ancient marine invertebrates has now been firmly pegged as lophophorates, a group whose living members include horseshoe worms and lamp shells, concludes an analysis of more than 1,500 fossils, including preserved soft tissue.
The soft-bodied creatures, encased in conical shells, concealed U-shaped guts and rings of tentacles called lophophores that surrounded their mouths. Fossil analysis suggests that hyoliths used those tentacles and spines, called helens, to trawl the seafloor more than 500 million years ago, researchers report online January 11 in Nature.
For years, paleontologists have argued over where on the tree of life these bottom-feeders belonged. Some scientists thought hyoliths were closely related to mollusks, while others thought the odd-looking creatures deserved a branch all their own. This new insight into hyolith anatomy “settles a long-standing paleontological debate,” the researchers write.
Dinosaur fashion, like that of humans, is subject to interpretation. Bony cranial crests, horns or bumps may have served to woo mates or help members of the same species identify one another. While the exact purpose of this skull decor is debated, the standout structures tended to come with an even more conspicuous trait: bigger bodies.
Terry Gates, a paleontologist at North Carolina State University in Raleigh, and colleagues noticed an interesting trend in the fossil record of theropods, a group of dinosaurs that includes Tyrannosaurus rex and the ancestors of birds. Bigger beasts often sported skeletal headgear. Across the family tree, Gates and his team analyzed 111 fossils dating from 65 million to 210 million years ago, and the trend held true. It makes sense: “Dinosaur size matters in terms of how they will be visually talking to one another,” says Gates. “When you’re smaller, your means of visual communication would be different than when you’re giant.”
The researchers also calculated that over time, theropod lineages with head ornaments evolved giant bodies (larger than 1,000 kilograms) 20 times faster on average than those without. Ornaments might have supersized some dinos, but researchers aren’t sure. The analysis, which appeared September 27 in Nature Communications, suggests theropods had to reach at least 55 kilograms to grow the headgear.
But among big-boned relatives of modern birds, skull toppers weren’t in vogue. Many of these dinos grew heavier than 55 kilograms, but they instead sported feathers that resembled those used by modern birds for flight. That might be because bigger, bolder feathers and showy headwear served similar ends. Gates speculates: “Once you have a signaling device in the form of a feather, why grow a bony cranial crest?” For these plumed dinosaurs, feathers were in and bony ornaments were out.
Size matters Many large theropods, a group of dinosaurs that includes Tyrannosaurus rex and the ancestors of birds, had bony head ornaments such as crests, horns and bumps. New research suggests theropods had to reach at least 55.2 kilograms to grow the cranial decor. But big-boned dinos related to modern birds lacked the ornaments. Instead, they were decked out in feathers resembling those used by modern birds for flight.
An enduring source of magma on Mars fueled volcanic eruptions for billions of years, clues inside a rock flung from the Red Planet reveal.
The newfound rock belongs to a batch of meteorites called shergottites that originated from the same Martian volcanic system, researchers report February 1 in Science Advances. But the new rock is considerably older than its counterparts. While previously discovered shergottites solidified from Martian magma between 427 million and 574 million years ago, the new rock formed around 2.4 billion years ago, chemical analyses show. Such a wide range of ages means that a volcanic system on Mars churned out hot rocks from a stable source of magma for nearly half of the planet’s history, says study coauthor Thomas Lapen, a geologist at the University of Houston. That endurance could help scientists better understand Mars’ interior. “These are some of the longest-lived volcanoes in the solar system,” Lapen says.
Lapen and colleagues studied elements inside a Martian meteorite discovered in Algerian desert in 2012. Some of those elements serve as stopwatches that record the history of the rock. Isotopes of beryllium and aluminum, formed during exposure to cosmic rays, reveal that the rock zipped through space for around 1 million years. The steady decay of carbon 14 — left behind after cosmic ray collisions — suggests that the rock landed on Earth roughly 2,300 years ago. By combining these two measurements, the researchers found that the meteorite probably blasted off Mars alongside other shergottites a little over a million years ago. This exodus probably followed a massive impact in Mars’ volcano-filled Tharsis region. The rocks share more than their exit route, the researchers found. Chemical similarities between the meteorites suggest that they all originate from the same source of hot rock deep within the Red Planet. That’s surprising given that the mix of radioactive elements inside the newfound meteorite suggests it solidified 1.8 billion years earlier than the next oldest shergottite, Lapen says.
Mars is known to have many volcanic systems across its surface, all fed by magma upwelling from the planet’s depths. Studies have previously suggested that some of these systems operated for billions of years. Though little is known about the Martian interior, many scientists had assumed that the magma feeding this volcanism changed over time as the Martian interior mixed. The absence of any difference in composition of the shergottites suggests Mars’ interior is relatively stagnant. That may result from Mars’ lack of plate tectonics, a process that helps blend Earth’s innards, Lapen proposes. Understanding the differences between Earth and Mars could help reveal why the two planets took such different trajectories, with Earth so much more life-friendly than Mars (SN: 5/2/15, p. 24). Similarities between the shergottites could have another explanation, says planetary scientist Stephanie Werner of the University of Oslo. Large impacts can melt rocks, resetting their age. The shergottites may have formed around the same time billions of years ago before some had their ages altered by impacts over time, she proposes.
Upcoming missions will help illuminate what’s going on beneath the Martian surface, says James Head, a planetary scientist at Brown University in Providence, R.I. NASA’s InSight lander, currently slated for launch in 2018, will use seismic activity to map the Red Planet’s interior.
In A.D. 185, Chinese records note the appearance of a “guest star” that then faded away over the span of several months. In 1572, astronomer Tycho Brahe and many others watched as a previously unknown star in the constellation Cassiopeia blasted out gobs of light and then eventually disappeared. And 30 years ago, the world witnessed a similar blaze of light from a small galaxy that orbits the Milky Way. In each case, humankind stood witness to a supernova — an exploding star — within or relatively close to our galaxy (representative border in gray, below).
Here’s a map of six supernovas directly seen by human eyes throughout history, and one nearby explosion that went unnoticed. Some were type 1a supernovas, the detonation of a stellar core left behind after a star releases its gas into space. Others were triggered when a star at least eight times as massive as the sun blows itself apart.
BOSTON — A fungus among us may tip the body toward developing asthma.
There’s mounting evidence that early exposure to microbes can protect against allergies and asthma (SN Online: 7/20/16). But “lo and behold, some fungi seem to put kids at risk for asthma,” microbiologist Brett Finlay said February 17 at a news conference during the annual meeting of the American Association for the Advancement of Science.
Infants whose guts harbored a particular kind of fungus — a yeast called Pichia — were more likely to develop asthma than babies whose guts didn’t have the fungus, Finlay reported. Studies in mice and people suggest that exposure to some fungi can both trigger and exacerbate asthma, but this is the first work linking asthma to a fungus in the gut microbiome of infants. Finlay, of the University of British Columbia in Vancouver, and his colleagues had recently identified four gut bacteria in Canadian infants that seem to provide asthma protection. To see if infants elsewhere were similarly protected by such gut microbes, he decided to look at another population of children with an asthma rate similar to Canada’s (about 10 percent). He and his colleagues sampled the gut microbes of 100 infants in rural Ecuador and followed up five years later.
The researchers identified several factors that might influence risk of developing asthma, such as exposure to antibiotics, having respiratory infections, and whether or not the infants were breastfed. Of the 29 infants in the high-risk asthma group, more than 50 percent had asthma by age 5, Finlay said.
Surprisingly, the strongest predictor of whether a child developed asthma wasn’t bacterial. It was the presence of Pichia. And the yeast wasn’t protective; it tipped the scales toward asthma.
Finlay speculated that molecules made by the fungi interact with the infants’ developing immune systems in a way that somehow increases asthma risk. It isn’t clear how the infants’ guts acquire the fungus; some species of Pichia are found in soil, others in raw milk and cheese. Finlay and his colleagues are now going to look for the fungus in Canadian children’s gut microbes..
The researchers also looked at other gut microbe‒related factors that upped the Ecuadorean children’s asthma risk. Children with access to clean water had higher asthma rates, Finlay said. While drinking clean water helps people avoid several ills such as cholera, the link to asthma highlights how some dirt can be protective, he said. “We’ve cleaned up our world too much.” This research underscores that caution should be used when generalizing about our intestinal flora. “What’s emerging is that it is very personalized,” gastroenterologist Eran Elinav of the Weizmann Institute of Science in Rehovot, Israel, said at the news conference. For example, evidence implicates some fungi in the development of inflammatory bowel disease, Elinav said, but it depends on the individual.
For a scientist, conducting a scientific study is walking into a minefield of potential biases that could detonate all over the results. Are the mice in the study randomly distributed among treatment groups? Does the person evaluating an animal’s behavior know what treatment the mouse got — and thus have an expectation for the outcome? Are there enough subjects in each group to reduce the odds that the results are due to chance?
“I think we’re getting increasingly better at identifying these risks and identifying clever and practical solutions,” says Hanno Würbel, an applied ethologist at the University of Bern in Switzerland. “But it’s not all obvious, and if you look back at the history of science you find that these methods have accumulated through a learning process.”
In theory, every time scientists design an experiment, they keep an eye out for these and other potential sources of bias. Then, when scientists submit the study design for approval or write journal articles about the work, they share that research design with their colleagues.
But scientists may be leaving some rather key bits out of their reports. Few animal research applications and published research reports include specific mentions of key factors used to eliminate bias in research studies, Würbel and colleagues Lucile Vogt, Thomas Reichlin and Christina Nathues report December 2 in PLOS Biology. The results suggest that the officials who approve animal research studies — and the scientists who peer review studies before publication — are trusting that researchers have accounted for potential biases, whether or not there is evidence to support that trust.
The team gained access to 1,277 applications for animal experiments submitted to the Swiss government in 2008, 2010 and 2012. The researchers examined the applications for seven common measures used to prevent bias: Randomization, calculations to make sure sample sizes were large enough, not telling the experimenter what treatment will be administered to the next animal, blinding the experimenter during testing to which animals received which treatment, criteria used to include or exclude subjects (say, the animal’s age or sex), explicitly stating the primary outcome to be measured and plans for statistical analysis of the data.
Most of the time, the applications didn’t mention how or whether any of those measures were considered. Scientists included statistical plans 2.4 percent of the time and sample size calculations only 8 percent of the time. Even the primary outcome variable — the main objective measured in the study — was mentioned in only 18.5 percent of the applications.
Würbel’s group also looked at 50 publications that came out of some of those animal research applications that were ultimately approved. Here, scientists were better about reporting their effort to stave off bias in their studies. If scientists mentioned one of the seven efforts to combat bias in their animal experiment applications, they were more likely to mention it when their final papers were published. But they still only reported the statistical plan 34 percent of the time, and none of the 50 papers reported sample size calculations. Switzerland’s animal research application process didn’t actually require that any of these measures of bias be disclosed, Würbel notes. But “unless [the licensing officials] know the studies have been designed rigorously, they can’t assess the benefit.” The implication, the researchers suggest, is that authorities approving the studies trusted that the scientists knew what they were doing, and that peer reviewers and editors trusted that the authors of journal articles took those forms of bias into account.
Was that trust well placed? To find out, Reichlin, Vogt and Würbel surveyed 302 Swiss scientists who do experiments on living organisms, asking about the efforts they made to combat bias, and how often they reported those efforts. When asked directly, scientists said that of course they control their studies for certain risks of bias. The vast majority — 90 percent — reported that they included the primary outcome variable, and 82 percent included a statistical analysis plan. A full 69 percent reported that they calculated their sample sizes. Most also reported that they wrote these antibias efforts into their latest published research article.
But when the team probed deeper, asking scientists specific questions about what methods they used to combat bias, “you find out they don’t know much about methods,” Würbel notes. Only about 44 percent of the researchers knew about the guidelines for how to report animal experiments, even though 51 percent of them had published in a journal that endorsed those guidelines, the researchers report December 2 in PLOS ONE.
“This is a type of empirical work that we need, to see how people think and what they do,” says John Ioannidis, a methods researcher at Stanford University in California.
Just because scientists aren’t reporting certain calculations or plans doesn’t mean that their research will be subject to those biases. But without efforts to rigorously prevent bias, it can sneak in — subjects that aren’t randomly assigned properly, or an experimenter who unconsciously leans toward one result or another. Too small of a sample size and a researcher could detect a difference that disappears in a larger group. If a researcher knows which animals got which treatment, they may unconsciously focus more carefully on some aspects of the treated animals’ behavior — ignoring similar behavior in the control. And that can result in studies that are tougher to replicate — or that can’t be replicated at all.
None of this means that scientists are ill-educated or performing science badly, notes Malcolm Macleod, a neurologist at the University of Edinburgh. “I think there’s a temptation to make this binary, [to say] people don’t know so we need to train them,” he says. “The fact is most scientists know a bit … [but] everyone has something they can do better.”
How do you make scientists take more actions against bias, and then report what they’ve done? Journals, funding bodies and agencies approving animal research projects could require more information of scientists. Journals could require checklists for reporting methods, for example. Journals or funding bodies could also require full preregistration of animal studies, where a scientist gives all the details of a study and how it will be analyzed before the experiments are ever performed. (Such pre-registration became mandatory for clinical studies in humans in the United States in 2000.) Detailed reporting isn’t complete insurance against an irreproducible result, but “the more information you have, the easier it is to reproduce,” says Vogt, who studies animal welfare at the University of Bern.
Some scientists might worry that preregistration is too onerous, or that it could straitjacket researchers into unproductive studies. It would be frustrating, after all, to be stuck with a hypothesis that is clearly not bearing out, when the data provide tantalizing hints of another path to pursue. But it’s possible to provide the flexibility to pursue interesting questions, while still making sure the studies are rigorous, Ioannidis says.
But when scientists don’t know sources of bias in the first place, more education might be a good place to start. “When I first came into the lab for my master’s thesis, I had a lot of information [about research design] but I wasn’t ready to apply it,” Vogt explains. “I needed guidance through the steps of how to plan an experiment, and how to plan to report the experiment afterward.” Education doesn’t stop when graduate students leave the classroom, and more continuing education might help scientists — students and emeriti alike — recognize unfamiliar sources of bias and provide tools to combat it.
Scientists have constructed five more yeast chromosomes from scratch. The new work, reported online March 9 in Science, brings researchers closer to completely lab-built yeast.
“We’re doing it primarily to learn a little more about how cells are wired,” says geneticist Jef Boeke of the New York University Langone Medical Center. But scientists might also be able to tinker with a synthetic yeast cell more efficiently than a natural one, allowing more precise engineering of everything from antiviral drugs to biofuels. Boeke was part of a team that reported the first synthetic yeast chromosome in 2014 (SN: 5/3/14, p. 7). Now, several hundred scientists in five countries are working to make all 16 Saccharomyces cerevisiae yeast chromosomes and integrate them into living cells. With six chromosomes finished, Boeke hopes the remaining 10 will be built by the end of 2017.
Each synthetic chromosome is based on one of S. cerevisiae’s, but with tweaks for efficiency. Researchers cut out stretches of DNA that can jump around and cause mutations, as well as parts that code for the same information multiple times.
When the researchers put chunks of synthetic DNA into yeast cells, the cells swapped out parts of their original DNA for the matching engineered snippets.
Yeast is a eukaryote — it stores its DNA in a nucleus, like human cells do. Eventually, this research could produce synthetic chromosomes for more complicated organisms, Boeke says, but such feats are still far in the future.
NEW ORLEANS — The tiniest electronic gadgets have nothing on a new data-storage device. Each bit is encoded using the magnetic field of a single atom — making for extremely compact data storage, although researchers have stored only two bits of data so far.
“If you can make your bit smaller, you can store more information,” physicist Fabian Natterer of the École Polytechnique Fédérale de Lausanne in Switzerland said March 16 at a meeting of the American Physical Society. Natterer and colleagues also reported the result in the March 9 Nature. Natterer and colleagues created the minuscule magnetic bits using atoms of holmium deposited on a surface of magnesium oxide. The direction of each atom’s magnetic field served as the 1 or 0 of a bit, depending on whether its north pole was pointing up or down.
Using a scanning tunneling microscope, the scientists could flip an atom’s magnetic orientation to switch a bit from 0 to 1. To read out the data, the researchers measured the current running through the atom, which depends on the magnetic field’s orientation. To ensure that the change in current observed after flipping a bit was due to a reorientation of the atom’s magnetic field, the team added bystander iron atoms to the mix and measured how the holmium atoms’ magnetic fields affected the iron atoms.
The work could lead to new hard drives that store data at much greater densities than currently possible. Today’s technologies require 10,000 atoms or more to store a single bit of information.
Natterer also hopes to use these mini magnets to construct materials with fine-tuned magnetic properties, building substances a single atom at a time. “You can play with them. It’s like Lego,” he says.
Glass frogs often start life with some tender care from a source scientists didn’t expect: frog moms.
Maternal care wouldn’t be news among mammals or birds, but amphibian parenting intrigues biologists because dads are about as likely as moms to evolve as the caregiver sex. And among New World glass frogs (Centrolenidae), what little parental care there is almost always is dad’s job — or so scientists thought, says Jesse Delia of Boston University. Months of strenuous nights searching streamside leaves in five countries, however, have revealed a widespread world of brief, but important, female care in glass frogs. In examining 40 species, Delia and Laura Bravo-Valencia, now at Corantioquia, a government environmental agency in Santa Fe de Antioquia, Colombia, found that often mothers lingered over newly laid eggs for several hours. By pressing maternal bellies against the brood, moms hydrated the jelly-glop of eggs and improved offspring chances of survival, Delia, Bravo-Valencia and Karen Warkentin, also of BU, report online March 31 in the Journal of Evolutionary Biology.
Glass frogs take their name from see-through skin on their bellies and, in certain cases, transparent organ tissues. (Some have clear hearts that reveal blood swishing through.) These frogs aren’t exactly obscure species, but until this field project, which stretched over six rainy seasons, female care in the family was unknown.
Female glass frogs may not cuddle their eggs for long, but it’s enough to matter, the researchers found. As is common in frogs, the mothers don’t drink with their mouths but absorb water directly through belly skin into a bladder. Moms pressing against a mass of newly laid eggs caused the protective goo to swell — perhaps by osmosis or peeing — and the mass to quadruple in size. For some of the glass frogs in the study, the youngsters were on their own once mom left. But at least hydration created an unpleasant amount of slime for a predator to bite through before getting to frog embryos. Night-hunting katydids in captivity, when offered a choice, barely nibbled at a hydrated mass of frog offspring, concentrating instead on eating an unhydrated clutch. In the field, when researchers removed about two dozen moms from their clutches in two species, mortality at least doubled to around 80 percent. Predators and dehydration caused the most deaths.
There are still more than 100 glass frog species that Delia and Bravo-Valencia haven’t yet watched in the wild. But the researchers did track down maternal care in 10 of 12 genera. Such a widespread form of maternal care probably evolved in the ancestor of all glass frogs, the researchers propose after analyzing glass frog family trees several ways.
In contrast, prolonged care from glass frog dads — rehydrating the egg mass as needed and fighting off predators such as hungry spiders — seems to have arisen independently later, at least twice. Across evolution in the animal kingdom, “usually we don’t see transitions from female to male care,” Delia says. “The pattern we found is completely bizarre.”
Why females started hanging around their eggs at all fascinates Hope Klug, an evolutionary biologist at the University of Tennessee at Chattanooga who studies parental care. In frogs, with eggs mostly fertilized externally, females could easily leave any care to dad.
“Parental care is perhaps more common and diverse in animals than we realize,” she says. “We just might have to look a little bit harder for it.”
Got a mouse in the house? Blame yourself. Not your housekeeping, but your species. Humans never intended to live a mouse-friendly life. But as we moved into a settled life, some animals — including a few unassuming mice — settled in, too. In the process, their species prospered — and took over the world.
The rise and fall of the house mouse’s fortunes followed the stability and instability of the earliest human settlements, a new study shows. By analyzing teeth from ancient mice and comparing the results to modern rodents hanging out near partially settled groups, scientists show that when humans began to settle down, one mouse species seemed to follow. When those people moved on, another species moved in. The findings reveal that human settlement took place long before agriculture began, and that vermin didn’t require a big storehouse of grain to thrive off of us.
Between 15,000 and 11,000 years ago (a time called the Natufian period), people began to form small stone settlements in what is now Israel and Jordan. They were not yet farming or storing grain, but they were living in a single place for a season or two, and coming back to that place relatively often. Those early settlers changed the ecosystem of the world around them — presenting new opportunities for local flora and fauna.
Lior Weissbrod, an archaeologist at the University of Haifa in Israel, started his career wanting to search for clues to the history of animal-human relationships. He was especially interested in animal remains. But, he admits, mouse teeth weren’t exactly his first choice. “[At] the site I was going to work on, the remains of larger animals were already studied,” he says. “I was left with the small mammals.”
Small mammals have even smaller teeth. The largest mouse molars are only about 1 millimeter long. This meant a lot of time sifting dirt through very fine mesh for Weissbrod. He collected 372 mouse teeth from the dirt of five different archaeological sites in modern-day Israel and Jordan, with remains dating from 11,000 to 200,000 years ago. He gave the teeth to his colleague Thomas Cucchi of the National Museum of Natural History in Paris, who developed a technique to classify the mouse teeth by species based on tiny differences in their shape. The first human settlements were only a few houses, but that’s a seismic shift if you’re the size of a mouse. Before the settlements were built, the mouse species Mus macedonicus scurried through the undergrowth. But after stone buildings arrived, another species dominated — Mus domesticu s. When humans left the settlements for about 1,000 years around 12,000 years ago, the reverse occurred: M. domesticus left and M. macedonicus moved back in. The two species probably competed against each other when humans were absent, Weissbrod hypothesizes. But when people were around, M. domesticus was better at taking advantage of human presence. They may have had more flexible diets — making it easier to live off our leavings — and less fear of people. “Once you get humans into the picture and human settlements … there’s a creation of a new habitat,” he explains. “This species [M. domesticus] is finally getting a break from the competition.”
Ancient samples alone would not be enough to establish whether one mouse species could out-compete another based on human settlement alone. For a modern approximation of the ancient, partially settled lifestyle, Weissbrod turned to the Maasai, a nomadic cattle-herding group in southern Kenya. “Maasai are nothing like ancient hunter-gatherers,” he notes. “But we look at specific things that make them comparable.” Maasai herders tend to live in small groups, and use those settlements over and over. “The Maasai aren’t sedentary, they are on the verge perhaps,” he explains. “So they move [often] but not to the extent of highly mobile nomadic groups, they move on a seasonal basis.”
Weissbrod headed to Kenya to collect 192 live, spiny mice, living around Maasai settlements. These mice could be divided into two species, Acomys wilsoni — the short-tailed version — and Acomys ignitus, with longer tails. An archaeologist used to working with dry and dusty fossils, Weissbrod had to adjust to working with live, wiggling rodents. “It took a conscious process of pushing myself to get over the ingrained aversion,” he says. Like their ancient kin, one modern spiny mouse had a competitive advantage when people were present. A. ignites made up 87 percent of the mice caught hanging out with the Maasai, but only 45 percent of the mice in non-settled area. The associations between mice and men allowed Weissbrod, Cucchi and their colleagues to show how house mice came to live alongside us — no grain or farming required. “We can show with a high degree of certainty now that mice became attached to us 3,000 years before farming,” Weissbrod says. “From that we learned hunter-gatherers were making the transition to sedentary lives before farming. They didn’t need the crops to make that transition.” Weissbrod and his colleagues published their findings March 27 in the Proceedings of the National Academy of Sciences.
“I thought it was wonderful,” Melinda Zeder, an archaeologist at the Smithsonian Institution in Washington, D.C., says of the study. “I really appreciated it on a number of levels.” Zeder said she was impressed that such a big finding could come from samples so incredibly small. “It’s not a keystone or early writing, it’s something most people overlook,” she says. “Out of the mouths of mice, we’re getting a wonderful view of a pivotal time in history.”
Other species certainly took advantage of human settlement, Zeder notes. Wolves and wild boar arrived and “auditioned themselves for a starring role as a domesticate.” A few of the friendlier ones began to interact more with people. Those people began to see the advantages of the animals. From wolves were born dogs, and from wild boar our pigs.
But when humans weren’t paying attention, other species moved in and thrived on their own. Mice aren’t the only vermin that have arrived to, as Weissbrod says, “domesticate themselves.” Sparrows, pigeons, rats and other species have come to take advantage of our presence. We may have never seen a use for them, but that doesn’t stop them from using us.
