This timid little fish escapes predators by injecting them with opioid-laced venom

This image shows the skull of the venomous species Meiacanthus grammistes.

Fang blennies are small fish with big teeth. Specifically, they have two large canine teeth that jut out of their lower jaw. Since blenny fish are only about two inches long, these "fangs" would be less than intimidating if not for the venom within. Blenny fish venom most likely causes a sudden drop in blood pressure in would-be predators, such as grouper fish, that have been bitten by blennies, researchers report on March 30 in Current Biology.

When the researchers did a proteomic analysis of extracted fang blenny venom, they found three venom components -- a neuropeptide that occurs in cone snail venom, a lipase similar to one from scorpions, and an opioid peptide. And, surprisingly, when they injected the blenny venom into lab mice, the mice didn't show any signs of pain.

"For the fang blenny venom to be painless in mice was quite a surprise," says study co-author Bryan Fry of University of Queensland. "Fish with venomous dorsal spines produce immediate and blinding pain. The most pain I've ever been in other than the time I broke my back was from a stingray envenomation. 'Sting'ray sounds so benign. They don't sting. They are pure hell."

Fang blenny venom, however, seems to have a very different effect on its victims. Since the researchers used rodents for the pain test, they can't entirely rule out the possibility of blenny venom causing pain in fish, but it seems plausible that the neuropeptide and opioid components may cause a sudden drop in blood pressure, most likely leaving the blenny's attacker disorientated and unable to give chase. "By slowing down potential predators, the fang blennies have a chance to escape," says Fry. "While the feeling of pain is not produced, opioids can produce sensations of extremely unpleasant nausea and dizziness [in mammals]."

Extracting the tiny fish's venom for chemical tests was no easy feat. When blenny fish bite an attacker, they only inject a tiny amount of venom, making it extremely difficult to collect enough for proteomic analyses. The researchers ended up using a quirky but labor-intensive method for extracting blenny venom: they would pluck the little fish out of their tanks, dangle a cotton swab in front of them so that the blenny would bite the cotton swab, and then suspended the cotton swabs in a solution that drew out the venom (after putting the fish back in the tank).

Nonvenomous fang blennies and other small fish capitalize on the venom's success by mimicking venomous fang blennies' colors and patterns. "Predatory fish will not eat those fishes because they think they are venomous and going to cause them harm, but this protection provided also allows some of these mimics to get very close to unsuspecting fish to feed on them, by picking on their scales as a micropredator," says study co-author Nicholas Casewell of the Liverpool School of Tropical Medicine. "All of this mimicry, all of these interactions at the community level, ultimately are stimulated by the venom system that some of these fish have."

Another surprise from the study was the evidence suggesting that fang blenny fangs evolved before the venom. "This is pretty unusual, because often what we've found -- for example, in snakes -- is that some sort of venom secretions evolved first, before the elaborate venom delivery mechanism evolved," says Casewell. Evolution favored the tiny fish with large teeth first and later found a way to enhance them with venom.

"These unassuming little fish have a really quite advanced venom system, and that venom system has a major impact on fishes and other animals in its community," says Casewell.

Read more at Science Daily

Melting sea ice may lead to more life in the sea

Melt ponds cover vast areas in the Arctic.

When spring arrives in the Arctic, both snow and sea ice melt, forming melt ponds on the surface of the sea ice. Every year, as global warming increases, there are more and larger melt ponds.

Melt ponds provide more light and heat for the ice and the underlying water, but now it turns out that they may also have a more direct and potentially important influence on life in the Arctic waters.

Mats of algae and bacteria can evolve in the melt ponds, which can provide food for marine creatures. This is the conclusion of researchers in the periodical, Polar Biology.

Own little ecosystems

• The melt ponds can form their own little ecosystem. When all the sea ice melts during the summer, algae and other organisms from melt ponds are released into the surrounding seawater. Some of this food is immediately ingested by creatures living high up in the water column. Other food sinks to the bottom and gets eaten by seabed dwellers, explains Heidi Louise Sørensen, who is the principal author of the scientific article, continuing:
• Given that larger and larger areas of melt ponds are being formed in the Arctic, we can expect the release of more and more food for creatures in the polar sea.

Heidi Louise Sørensen studied the phenomenon in a number of melt ponds in North-Eastern Greenland as part of her PhD thesis at University of Southern Denmark (SDU).

Bo Thamdrup and Ronnie Glud of SDU, and Erik Jeppesen and Søren Rysgaard of Aarhus University also contributed to the work.

Food for seals and sea cucumbers

In the upper part of the water column it is mainly krill and copepods that benefit from the nutrient-rich algae and bacteria from melt ponds. These creatures are eaten by various larger animals, ranging from amphipods to fish, seals and whales. Deeper down, it is seabed dwellers such as sea cucumbers and brittle stars that benefit from the algae that sink down.

For some time now, researchers have been aware that simple biological organisms can evolve in melt ponds -- they may even support very diverse communities. But so far it has been unclear why sometimes there are many organisms in the ponds, and on other occasions virtually none.

According to the new study, 'nutrients' is the keyword. When nutrients such as phosphorus and nitrogen find their way into a melt pond, entire communities of algae and micro-organisms can flourish.

From the Siberian tundra

Nutrients can find their way into a melt pond in a variety of ways, For example, they can be washed in with waves of sea water; they can be transported by dust storms from the mainland (for example, from the Siberian tundra); or they can be washed with earth from the coast out on the ice, when it rains.

Finally, migratory birds or other larger animals resting on the ice can leave behind sources of nutrient.

• Climate change is accompanies by more storms and more precipitation, and we must expect that more nutrients will be released from the surroundings into the melt ponds. These conditions, plus the fact that the distribution of areas of melt ponds is increasing, can contribute to increased productivity in plant and animal life in the Arctic seas, says Professor Ronnie Glud of the Department of Biology at SDU.

Warmer and more windy

There are further factors that may potentially contribute to increased productivity in the Arctic seas:

• When the sea ice disappears, light can penetrate down into the water.
• water. When it gets warmer on the mainland, this creates more melt water, which can flow out into the sea, carrying nutrients in its wake.

BOX What the researchers did

Six melt ponds in Young Sound in North-Eastern Greenland were selected: two natural and four artificial basins. Phosphorous and nitrogen (nutrients, which are also known from common garden fertilizer) were added in various combinations to four ponds, while two served as control ponds. For a period of up to 13 days Heidi Louise Sørensen measured many different parameters in the melt water, including the content of Chlorophyll a: a pigment that enables algae to absorb energy from light. The chlorophyll content of the phosphorus- and nitrogen-enriched ponds was 2 to 10 times higher than in the control ponds and testifies to an increased content of algae.

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Why are primates big-brained? Researchers' answer is food for thought

Brain size in primates is predicted by diet, an analysis by a team of NYU anthropologists indicates. Above, a chimpanzee eating fruit.

Brain size in primates is predicted by diet, an analysis by a team of New York University anthropologists indicates. These results call into question "the social brain hypothesis," which has posited that humans and other primates are big-brained due to factors pertaining to sociality.

The findings, which appear in the journal Nature Ecology and Evolution, reinforce the notion that both human and non-human primate brain evolution may be driven by differences in feeding rather than in socialization.

"Are humans and other primates big-brained because of social pressures and the need to think about and track our social relationships, as some have argued?" asks James Higham, an assistant professor in NYU's Department of Anthropology and a co-author of the new analysis. "This has come to be the prevailing view, but our findings do not support it -- in fact, our research points to other factors, namely diet."

"Complex foraging strategies, social structures, and cognitive abilities, are likely to have co-evolved throughout primate evolution," adds Alex DeCasien, an NYU doctoral candidate and lead author of the study. "However, if the question is: 'Which factor, diet or sociality, is more important when it comes to determining the brain size of primate species?' then our new examination suggests that factor is diet."

The social brain hypothesis sees social complexity as the primary driver of primate cognitive complexity, suggesting that social pressures ultimately led to the evolution of the large human brain. While some studies have shown positive relationships between relative brain size and group size, other studies which examined the effects of different social or mating systems have revealed highly conflicting results, raising questions about the strength of the social brain hypothesis.

In the Nature Ecology and Evolution study, the researchers, who also included Scott Williams, an assistant professor of anthropology at NYU, examined more than 140 primate species -- or more than three times as many as previous studies -- and incorporated more recent evolutionary trees, or phylogenies. They took into account food consumption across the studied species -- folivores (leaves), frugivores (fruit), frugivores/folivores, and omnivores (addition of animal protein) -- as well as several measures of sociality, such as group size, social system, and mating system.

Their results showed that brain size is predicted by diet rather than by the various measures of sociality -- after controlling for body size and phylogeny. Notably, frugivores and frugivore/folivores exhibit significantly larger brains than folivores and, to a lesser extent, omnivores show significantly larger brains than folivores.

The researchers caution that the results do not reveal an association between brain size and fruit or protein consumption on a within-species level; rather, they note, they are evidence of the cognitive demands required by different species to obtain certain foods.

Read more at Science Daily

A seismic mapping milestone

This visualization is the first global tomographic model constructed based on adjoint tomography, an iterative full-waveform inversion technique. The model is a result of data from 253 earthquakes and 15 conjugate gradient iterations with transverse isotropy confined to the upper mantle.

Because of Earth's layered composition, scientists have often compared the basic arrangement of its interior to that of an onion. There's the familiar thin crust of continents and ocean floors; the thick mantle of hot, semisolid rock; the molten metal outer core; and the solid iron inner core.

But unlike an onion, peeling back Earth's layers to better explore planetary dynamics isn't an option, forcing scientists to make educated guesses about our planet's inner life based on surface-level observations. Clever imaging techniques devised by computational scientists, however, offer the promise of illuminating Earth's subterranean secrets.

Using advanced modeling and simulation, seismic data generated by earthquakes, and one of the world's fastest supercomputers, a team led by Jeroen Tromp of Princeton University is creating a detailed 3-D picture of Earth's interior. Currently, the team is focused on imaging the entire globe from the surface to the core-mantle boundary, a depth of 1,800 miles.

These high-fidelity simulations add context to ongoing debates related to Earth's geologic history and dynamics, bringing prominent features like tectonic plates, magma plumes, and hotspots into view. In 2016, the team released its first-generation global model. Created using data from 253 earthquakes captured by seismograms scattered around the world, the team's model is notable for its global scope and high scalability.

"This is the first global seismic model where no approximations -- other than the chosen numerical method -- were used to simulate how seismic waves travel through Earth and how they sense heterogeneities," said Ebru Bozdag, a coprincipal investigator of the project and an assistant professor of geophysics at the University of Nice Sophia Antipolis. "That's a milestone for the seismology community. For the first time, we showed people the value and feasibility of running these kinds of tools for global seismic imaging."

The project's genesis can be traced to a seismic imaging theory first proposed in the 1980s. To fill in gaps within seismic data maps, the theory posited a method called adjoint tomography, an iterative full-waveform inversion technique. This technique leverages more information than competing methods, using forward waves that travel from the quake's origin to the seismic receiver and adjoint waves, which are mathematically derived waves that travel from the receiver to the quake.

The problem with testing this theory? "You need really big computers to do this," Bozdag said, "because both forward and adjoint wave simulations are performed in 3-D numerically."

In 2012, just such a machine arrived in the form of the Titan supercomputer, a 27-petaflop Cray XK7 managed by the US Department of Energy's (DOE's) Oak Ridge Leadership Computing Facility (OLCF), a DOE Office of Science User Facility located at DOE's Oak Ridge National Laboratory. After trying out its method on smaller machines, Tromp's team gained access to Titan in 2013 through the Innovative and Novel Computational Impact on Theory and Experiment, or INCITE, program.

Working with OLCF staff, the team continues to push the limits of computational seismology to deeper depths.

Stitching together seismic slices

When an earthquake strikes, the release of energy creates seismic waves that often wreak havoc for life at the surface. Those same waves, however, present an opportunity for scientists to peer into the subsurface by measuring vibrations passing through Earth.

As seismic waves travel, seismograms can detect variations in their speed. These changes provide clues about the composition, density, and temperature of the medium the wave is passing through. For example, waves move slower when passing through hot magma, such as mantle plumes and hotspots, than they do when passing through colder subduction zones, locations where one tectonic plate slides beneath another.

Each seismogram represents a narrow slice of the planet's interior. By stitching many seismograms together, researchers can produce a 3-D global image, capturing everything from magma plumes feeding the Ring of Fire, to Yellowstone's hotspots, to subducted plates under New Zealand.

This process, called seismic tomography, works in a manner similar to imaging techniques employed in medicine, where 2-D x-ray images taken from many perspectives are combined to create 3-D images of areas inside the body.

In the past, seismic tomography techniques have been limited in the amount of seismic data they can use. Traditional methods forced researchers to make approximations in their wave simulations and restrict observational data to major seismic phases only. Adjoint tomography based on 3-D numerical simulations employed by Tromp's team isn't constrained in this way. "We can use the entire data -- anything and everything," Bozdag said.

Running its GPU version of the SPECFEM3D_GLOBE code, Tromp's team used Titan to apply full-waveform inversion at a global scale. The team then compared these "synthetic seismograms" with observed seismic data supplied by the Incorporated Research Institutions for Seismology (IRIS), calculating the difference and feeding that information back into the model for further optimization. Each repetition of this process improves global models.

"This is what we call the adjoint tomography workflow, and at a global scale it requires a supercomputer like Titan to be executed in reasonable timeframe," Bozdag said. "For our first-generation model, we completed 15 iterations, which is actually a small number for these kinds of problems. Despite the small number of iterations, our enhanced global model shows the power of our approach. This is just the beginning, however."

Automating to augment

For its initial global model, Tromp's team selected earthquake events that registered between 5.8 and 7 on the Richter scale -- a standard for measuring earthquake intensity. That range can be extended slightly to include more than 6,000 earthquakes in the IRIS database -- about 20 times the amount of data used in the original model.

Getting the most out of all the available data requires a robust automated workflow capable of accelerating the team's iterative process. Collaborating with OLCF staff, Tromp's team has made progress toward this goal.

For the team's first-generation model, Bozdag carried out each step of the workflow manually, taking about a month to complete one model update. Team members Matthieu Lefebvre, Wenjie Lei, and Youyi Ruan of Princeton University and the OLCF's Judy Hill developed new automated workflow processes that hold the promise of reducing that cycle to a matter of days.

"Automation will really make it more efficient, and it will also reduce human error, which is pretty easy to introduce," Bozdag said.

Additional support from OLCF staff has contributed to the efficient use and accessibility of project data. Early in the project's life, Tromp's team worked with the OLCF's Norbert Podhorszki to improve data movement and flexibility. The end result, called Adaptable Seismic Data Format (ASDF), leverages the Adaptable I/O System (ADIOS) parallel library and gives Tromp's team a superior file format to record, reproduce, and analyze data on large-scale parallel computing resources.

In addition, the OLCF's David Pugmire helped the team implement in situ visualization tools. These tools enabled team members to check their work more easily from local workstations by allowing visualizations to be produced in conjunction with simulation on Titan, eliminating the need for costly file transfers.

"Sometimes the devil is in the details, so you really need to be careful and know what you're looking at," Bozdag said. "David's visualization tools help us to investigate our models and see what is there and what is not."

With visualization, the magnitude of the team's project comes to light. The billion-year cycle of molten rock rising from the core-mantle boundary and falling from the crust -- not unlike the motion of globules in a lava lamp -- takes form, as do other geologic features of interest.

At this stage, the resolution of the team's global model is becoming advanced enough to inform continental studies, particularly in regions with dense data coverage. Making it useful at the regional level or smaller, such as the mantle activity beneath Southern California or the earthquake-prone crust of Istanbul, will require additional work.

"Most global models in seismology agree at large scales but differ from each other significantly at the smaller scales," Bozdag said. "That's why it's crucial to have a more accurate image of Earth's interior. Creating high-resolution images of the mantle will allow us to contribute to these discussions."

Digging deeper

To improve accuracy and resolution further, Tromp's team is experimenting with model parameters under its most recent INCITE allocation. For example, the team's second-generation model will introduce anisotropic inversions, which are calculations that better capture the differing orientations and movement of rock in the mantle. This new information should give scientists a clearer picture of mantle flow, composition, and crust-mantle interactions.

Additionally, team members Dimitri Komatitsch of Aix-Marseille University in France and Daniel Peter of King Abdullah University in Saudi Arabia are leading efforts to update SPECFEM3D_GLOBE to incorporate capabilities such as the simulation of higher-frequency seismic waves. The frequency of a seismic wave, measured in Hertz, is equivalent to the number of waves passing through a fixed point in one second. For instance, the current minimum frequency used in the team's simulation is about 0.05 hertz (1 wave per 20 seconds), but Bozdag said the team would also like to incorporate seismic waves of up to 1 hertz (1 wave per second). This would allow the team to model finer details in Earth's mantle and even begin mapping Earth's core.

To make this leap, Tromp's team is preparing for Summit, the OLCF's next-generation supercomputer. Set to arrive in 2018, Summit will provide at least five times the computing power of Titan. As part of the OLCF's Center for Accelerated Application Readiness, Tromp's team is working with OLCF staff to take advantage of Summit's computing power upon arrival.

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Male or female? Scientist challenges evidence of sex differences among dinosaurs

Dr. Jordan Mallon stands in the Canadian Museum of Nature's collections among replicas of skulls of dinosaurs previously studied for sexual dimorphism: Tyrannosaurus rex (large skull), Allosaurus fragilis (black skull), Protoceratops andrewsi and Stegoceras validum (in his hand).

A paleontologist at the Canadian Museum of Nature is countering decades of studies that assert that some dinosaurs can be identified as male or female based on the shapes and sizes of their bones.

Dr. Jordan Mallon, a dinosaur specialist at the museum, argues instead that the fossil evidence for these distinctions is inconclusive and, as a result, it might be time to "rewrite the textbooks." His report, published today in the online journal Paleobiology, focusses on the biological principle of sexual dimorphism, where males and females of a species can be distinguished based on physical characteristics other than sexual organs.

"I'm not saying that dinosaurs were not dimorphic, but I am saying that there's no existing fossil evidence to suggest that they were. The jury is still out," says Mallon.

Mallon made his assessment by revisiting previous studies attributing sexual dimorphism to dinosaurs. The problem, he explains, is that some of those studies not only relied on small sample sizes, but, more importantly, they did not properly analyze the statistical data, which led to invalid conclusions.

"Essentially, if you go back and recrunch the data of those original studies using proper statistical tests such as mixture modelling, then there's no dimorphism," explains Mallon. "While others have doubted the existence of dimorphism from the dinosaur fossil record, this is the first published report to show that's the case."

Mallon reviewed data on nine species, ranging from horned dinosaurs, to stegosaurs to meat-eating dinos. Among the studies was a seminal 1976 paper assigning sexual dimorphism to about 20 specimens of a horned dinosaur called Protoceratops andrewsi. The author's analysis said males could be distinguished from females by a broader frill and larger bump on the nose. While the study used a large sample size, Mallon's retesting of the data shows there is not enough evidence to separate the specimens into two distinct groups based on the shapes of their bones.

Mallon notes that there are ways of distinguishing male dinosaurs from females, but, to date, these sorts of data are sparse and do little to inform an understanding about whether the sexes differed in their external anatomy.

"There are ways of determining the sex of individual females, for example, as some fossils have been found with eggs preserved inside them," he explains. Mallon also notes that researchers can look for medullary bone, which is a spongy bone deposited in the long bones of egg-laying females, as seen in birds today.

"What we need to do is examine dinosaur specimens that we can positively identify as females, and if you can survey a large enough population of them, you can then say this is what we expect females to look like. One can then study the remainder of the population to compare which ones look like the females that we already know, and which ones don't. Those would be the males," says Mallon.

Mallon maintains that he would not be surprised if dimorphism did exist among some dinosaurs, because the phenomenon is seen in living animals such as birds and crocodiles, which are the nearest living relatives of dinosaurs. Male crocodiles, for example, are larger than females, and the male peacock has a large colourful tail.

The challenge for paleontologists is to find fossils of a given species in a large enough number and of similar age to do a proper statistical analysis. And, as Mallon points out, the studies to date are lacking in that regard.

Read more at Science Daily

Poor outlook for biodiversity in Antarctica

These are Cabeater seals on an ice floe in the Antarctic Peninsula area.

The popular view that Antarctica and the Southern Ocean are in a much better environmental shape than the rest of the world has been brought into question in a study publishing on March 28 in the open access journal PLOS Biology, by an international team lead by Steven L. Chown and Monash University scientists.

The study compared the position of Antarctic biodiversity and its management with that globally using the Convention on Biological Diversity's (CBD) Aichi targets. The Aichi targets are part of the Strategic Plan for Biodiversity 2011-2020, adopted under the CBD, to assess progress in halting global biodiversity loss. Yet they have never been applied to Antarctica and the Southern Ocean -- areas which together account for about 10% of the planet's surface.

The study found that the difference between the status of biodiversity in the Antarctic and the rest of the world was negligible.

"The results have been truly surprising," said lead author and Head of the School of Biological Sciences at Monash, Professor Steven Chown.

"While in some areas, such as invasive species management, the Antarctic region is doing relatively well, in others, such as protected area management and regulation of bioprospecting, it is lagging behind," he said. "Overall, the biodiversity and conservation management outlook for Antarctica and the Southern Ocean is no different to that for the rest of the planet."

"Despite our findings, there are great opportunities for positive action," said Monash co-author Professor Melodie McGeoch. "The agreements under the Antarctic Treaty System lend themselves to effective action, and nations have recently reinforced their desire to protect the region's biodiversity."

This latest analysis by scientists ensures that future assessments made under the Strategic Plan for Biodiversity 2011-2020 will be truly global.

"It will also help inform global progress towards achieving the United Nation's Sustainable Development Goals," Professor McGeoch said.

From Science Daily

Hair spacing keeps honeybees clean during pollination

A honeybee is covered in commercial pollen.

With honeybee colony health wavering and researchers trying to find technological ways of pollinating plants in the future, a new Georgia Tech study has looked at how the insects do their job and manage to stay clean.

According to the study, a honeybee can carry up to 30 percent of its body weight in pollen because of the strategic spacing of its nearly three million hairs. The hairs cover the insect's eyes and entire body in various densities that allow efficient cleaning and transport.

The research found that the gap between each eye hair is approximately the same size as a grain of dandelion pollen, which is typically collected by bees. This keeps the pollen suspended above the eye and allows the forelegs to comb through and collect the particles. The legs are much hairier and the hair is very densely packed -- five times denser than the hair on the eyes. This helps the legs collect as much pollen as possible with each swipe. Once the forelegs are sufficiently scrubbed and cleaned by the other legs and the mouth, they return to the eyes and continue the process until the eyes are free of pollen.

The Georgia Tech team tethered bees and used high speed cameras to create the first quantified study of the honeybee cleaning process. They watched as the insects were able to remove up to 15,000 particles from their bodies in three minutes.

"Without these hairs and their specialized spacing, it would be almost impossible for a honeybee to stay clean," said Guillermo Amador, who led the study while pursuing his doctoral degree at Georgia Tech in mechanical engineering.

This was evident when Amador and the team created a robotic honeybee leg to swipe pollen-covered eyes. When they covered the leg with wax, the smooth, hairless leg gathered four times less pollen.

The high-speed videos also revealed something else.

"Bees have a preprogrammed cleaning routine that doesn't vary," said Marguerite Matherne, a Ph.D. student in the George W. Woodruff School of Mechanical Engineering. "Even if they're not very dirty in the first place, bees always swipe their eyes a dozen times, six times per leg. The first swipe is the most efficient, and they never have to brush the same area of the eye twice."

The research also found that pollenkitt, the sticky, viscous fluid found on the surface of pollen grains, is essential. When the fluid was removed from pollen during experiments, bees accumulated half as much.

"If we can start learning from natural pollinators, maybe we can create artificial pollinators to take stress off of bees," said David Hu, a professor in the Woodruff School of Mechanical Engineering and School of Biological Sciences. "Our findings may also be used to create mechanical designs that help keep micro and nanostructured surfaces clean."

Read more at Science Daily

Mouse in the house tells tale of human settlement

A mouse from a Maasai village in southern Kenya.

Long before the advent of agriculture, hunter-gatherers began putting down roots in the Middle East, building more permanent homes and altering the ecological balance in ways that allowed the common house mouse to flourish, new research in the Proceedings of the National Academy of Sciences indicates.

"The research provides the first evidence that, as early as 15,000 years ago, humans were living in one place long enough to impact local animal communities -- resulting in the dominant presence of house mice," said Fiona Marshall, study co-author and a professor of anthropology at Washington University in St. Louis. "It's clear that the permanent occupation of these settlements had far-reaching consequences for local ecologies, animal domestication and human societies."

Marshall, a noted expert on animal domestication, considers the research exciting because it shows that settled hunter-gatherers rather than farmers were the first people to transform environmental relations with small mammals. By providing stable access to human shelter and food, hunter-gatherers led house mice down the path to commensalism, an early phase of domestication in which a species learns how to benefit from human interaction.

The findings have broad implications for the processes that led to animal domestication.

"The findings provide clear evidence that the ways humans have shaped the natural world are tied to varying levels of human mobility," said Marshall, the James W. and Jean L. Davis Professor in Arts & Sciences. "They suggest that the roots of animal domestication go back to human sedentism thousands of years prior to what has long been considered the dawn of agriculture."

Led by Thomas Cucchi of National Center for Scientific Research in Paris, France, and Lior Weissbrod of the University of Haifa in Israel, the study set out to explain large swings in the ratio of house mice to wild mice populations found during excavations of different prehistoric periods at an ancient Natufian hunter-gatherer site in the Jordan Valley of Israel.

Examining tiny species-related variations in the molar shapes of fossilized mice teeth dating back as far as 200,000 years, the team built a timeline showing how the populations of different mice fluctuated at the Natufian site during periods of varying human mobility.

The analysis revealed that human mobility influenced competitive relationships between two species of mice -- the house mouse (Mus musculus domesticus)and a short-tailed field mouse (M. macedonicus) -- that continue to live in and around modern settlements in Israel. These relationships are analogous to those of another pair of species called spiny mice which Weissbrod and Marshall discovered among semi-nomadic Maasai herders in southern Kenya.

Findings indicate that house mice began embedding themselves in the Jordan Valley homes of Natufian hunter-gatherers about 15,000 years ago, and that their populations rose and fell based on how often these communities picked up and moved to new locations.

When humans stayed in the same places for long runs of time, house mice out-competed their country cousins to the point of pushing most of them outside the settlement. In periods where drought, food shortages or other conditions forced hunter-gatherers to relocate more often, the populations of house mice and field mice reached a balance similar to that found among modern Maasai herders with similar mobility patterns.

The study confirms that house mice were already a fixture in the domiciles of eastern Mediterranean hunter-gatherer villages more than 3,000 years before the earliest known evidence for sedentary agriculture.

It suggests that the early hunter-gatherer settlements transformed ecological interactions and food webs, allowing house mice that benefited from human settlements to out-compete wild mice and establish themselves as the dominant population.

"The competition between commensal house mice and other wild mice continued to fluctuate as humans became more mobile in arid periods and more sedentary at other times -- indicating the sensitivity of local environments to degrees of human mobility and the complexity of human environmental relationships going back in the Pleistocene," said Weissbrod, currently a research fellow at the Zinman Institute of Archaeology at the University of Haifa.

Weissbrod's research involves analysis of microvertebrate remains from a wide range of prehistoric and historic sites in Israel and the Caucasus dealing with paleoecology and human-ecosystem interactions.

A 2010 graduate of the doctoral program in archaeological anthropology at Washington University, he began research for this study as part of a dissertation examining fluctuations in populations of mice and other small animals living around Maasai cattle herding settlements in Kenya.

Marshall helped Weissbrod to develop the ethnographic context for underlying research questions about the ecological impact of human mobility. Together they built field-based ecological frameworks for understanding changing animal human interactions through time focusing on mice and donkeys.

Working from his lab in Paris, Cucchi used a new technique called geometric morphometrics to identify the mouse fossils and reliably distinguish telltale differences in the miniscule remains of house mice and wild species. The method relies on high resolution imaging and digital analysis to categorize species-related variations in molar outlines nearly as thin as a single millimeter.

The findings, and the techniques used to document them, are important to archaeological research in a broader sense because they lend further support to the idea that fluctuations in ancient mouse populations can be used as a proxy for tracking ancient shifts in human mobility, lifestyle and food domestication.

Read more at Science Daily

Lead exposure in childhood linked to lower IQ, lower status jobs, as adults

People screened for blood-lead level at age 11 and IQ-tested in childhood and at age 38, reveal an association between childhood lead exposures and a decline in IQ. Higher doses led to greater losses, including having occupational standing lower than their parents.

A long-term study of more than 500 children who grew up in the era of leaded gasoline has shown that their exposure to the powerful neurotoxin may have led to a loss of intelligence and occupational standing by the time they reached age 38.

The effects are slight, but significant, showing that the higher the blood lead level in childhood, the greater the loss of IQ points and occupational status in adulthood. The study appears Wednesday in the Journal of the American Medical Association.

Study participants are part of a life-long examination of more than 1,000 people born in Dunedin, New Zealand in 1972 and 1973. During their childhood, New Zealand had some of the highest gasoline lead levels in the world.

From birth to adulthood, these people have regularly been assessed for cognitive skills such as perceptual reasoning and working memory. At age 11, blood samples were collected from 565 of them which were then tested for lead.

Participants who were found to carry more than 10 micrograms of lead per deciliter of blood at age 11 had IQs at age 38 that were, on average, 4.25 points lower than their less lead-exposed peers. They were also found to have lost IQ points relative to their own childhood scores.

The study found that for each 5-microgram increase in blood lead, a person lost about 1.5 IQ points.

The mean blood lead level of the children at age 11 was 10.99 micrograms per deciliter of blood, slightly higher than the historical "level of concern" for lead exposure. Today's reference value at which the CDC recommends public health intervention is half that, 5 micrograms per deciliter, a level which 94 percent of children in the study exceeded. No safe blood lead level in children has been identified.

"This is historical data from an era when lead levels like these were viewed as normal in children and not dangerous, so most of our study participants were never given any special treatment," said Terrie Moffitt, the senior author of the study and Duke's Nannerl O. Keohane University Professor of psychology & neuroscience and psychiatry & behavioral sciences.

"This case is different from the one in Flint, Michigan and other cities where lead in the drinking water has led public health officials to begin special interventions for those children," Moffitt said. Flint's children are receiving regular blood monitoring and expanded early childhood education, behavioral health services and special nutrition with the federal government's support. "Interventions of this sort are intended to forestall the sorts of effects we've measured in this study," she said.

What makes the New Zealand case an important natural experiment is that automobile traffic goes through all neighborhoods. Unlike exposures to leaded paint or lead pipes in older structures, which pose more of a threat to poorer families, the exposure to leaded gasoline fumes was distributed relatively evenly across all social strata.

Beginning in the 1920s, a compound called tetra-ethyl-lead was added to gasoline for its ability to boost octane ratings and raise engine power. The lead itself didn't burn however, and emerged from tailpipes as elemental lead and lead oxides which settled as a particulate in soils around areas where cars were common.

Soil hangs on tightly to lead particles and soils next to busy roads have been found to have the highest lead concentrations from the leaded gasoline era. Children playing outside were prone to either breathe in lead-laden dust, or swallow small amounts of leaded soil.

In either case, lead can accumulate in the child's bloodstream. It then settles into the bones, teeth and soft tissues and accumulates in the body over time.

Leaded gasoline was phased out in the U.S. and New Zealand between the mid-1970s and the mid-1990s, but is still used in some Asian and middle eastern countries.

"Regardless of where you start in life, lead is going to exert a downward pull," said Avshalom Caspi, Edward M. Arnett Professor of psychology & neuroscience and psychiatry & behavioral sciences at Duke, who is a co-author on the paper. A neurotoxin exposure that affects all parts of society relatively equally would move the entire curve of IQ and social status downward. "If everyone takes a hit from environmental pollutants, society as a whole suffers."

The study also compared changes in social standing using a measure from the New Zealand government that plots families on a 6-point scale. The childhood social status of each child's family was compared to their adult standing at age 38. Children who were over 10 micrograms of lead attained occupations with socioeconomic status levels four-tenths lower than their less-exposed peers.

"The downward social mobility we see mirrors the trend in IQ," said Aaron Reuben, a Duke psychology graduate student who is first author on the study. After various statistical controls were applied to the data, "the decline in occupational status is partially but significantly explained by the loss of IQ," he said. "If you're above the historic level of concern (for lead exposure), you're doing worse on both."

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How a young-looking lunar volcano hides its true age

The feature known as Ina, as seen by NASA's Lunar Reconnaissance Orbiter, was likely formed by an eruption of fluffy 'magmatic foam,' new research shows.

While orbiting the Moon in 1971, the crew of Apollo 15 photographed a strange geological feature -- a bumpy, D-shaped depression about two miles long and a mile wide -- that has fascinated planetary scientists ever since. Some have suggested that the feature, known as Ina, is evidence of a volcanic eruption Moon within the past 100 million years -- a billion years or so after most volcanic activity on the Moon is thought to have ceased.

But new research led by Brown University geologists suggests that Ina is not so young after all. The analysis, published in the journal Geology, concludes that the feature was actually formed by an eruption around 3.5 billion years ago, around the same age as the dark volcanic deposits we see on the Moon's nearside. It's the peculiar type of lava that erupted from Ina that helps hide its age, the researchers say.

"As interesting as it would be for Ina to have formed in the recent geologic past, we just don't think that's the case," said Jim Head, co-author of the paper and professor in Brown's Department of Earth, Environmental and Planetary Sciences. "The model we've developed for Ina's formation puts it firmly within the period of peak volcanic activity on the Moon several billion years ago."

Youthful appearance

Ina sits near the summit of a gently sloped mound of basaltic rock, leading many scientists to conclude that it was likely the caldera of an ancient lunar volcano. But just how ancient wasn't clear. While the flanks of the volcano look billions of years old, the Ina caldera itself looks much younger. One sign of youth is its bright appearance relative to its surroundings. The brightness suggests Ina hasn't had time to accumulate as much regolith, the layer of loose rock and dust that builds up on the surface over time.

Then there are Ina's distinctive mounds -- 80 or so smooth hills of rock, some standing as tall as 100 feet, which dominate the landscape within the caldera. The mounds appear to have far fewer impact craters on them compared to the surrounding area, another sign of relative youth. Over time, it's expected that a surface should accumulate craters of various sizes at fairly constant rates. So scientists use the number and size of craters to estimate the relative age of a surface. In 2014, a team of researchers did a careful crater-count on Ina's mounds and concluded that they must have been formed by lava that erupted to the surface within the last 50 to 100 million years.

"That was a really puzzling finding," Head said. "I think most people agree that the volcano Ina sits on was formed billions of years ago, which means there would have been a pause in volcanic activity for a billion years or more before the activity that formed Ina. We wanted to see if there might be something about geologic structure within Ina that throws off our estimation of its age."

Not so young?

The researchers looked at well-studied volcanoes on Earth that might be similar to Ina. Ina appears to be a pit crater on a shield volcano, a gently sloping mountain similar to the Kilauea volcano in Hawaii. Kilauea has a pit crater similar to Ina known as the Kilauea Iki crater, which erupted in 1959.

As lava from that eruption solidified, it created a highly porous rock layer inside the pit, with underground vesicles as large as three feet in diameter and surface void space as deep as two feet. That porous surface, Head and his colleagues say, is created by the nature of the lava erupted in the late stages of events like this one. As the subsurface lava supply starts to diminish, it erupts as "magmatic foam" -- a bubbly mixture of lava and gas. When that foam cools and solidifies, it forms the highly porous surface.

The researchers suggest that an Ina eruption would have also produced magmatic foam. And because of the Moon's decreased gravity and nearly absent atmosphere, the lunar foam would have been even fluffier than on Earth, so it's expected that the structures within Ina are even more porous than on Earth.

It's the high porosity of those surfaces that throws off date estimates for Ina, both by hiding the buildup of regolith and by throwing off crater counts.

A highly porous surface, the researchers say, would allow loose rock and dust to filter into surface void space, making it appear as though less regolith has built up. That process would be perpetuated by seismic shaking in the region, much of which is caused by ongoing meteor impacts. "It's like banging on the side of a sieve to make the flour go through," Head said. "Regolith is jostled into holes rather than sitting on the surface, which makes Ina look a lot younger."

Porosity could also skew crater counts. Laboratory experiments using a high-speed projectile cannon have shown that impacts into porous targets make much smaller craters. Because of Ina's extreme porosity, the researchers say, its craters are much smaller than they would normally be, and many craters might not be visible at all. That could drastically alter the age estimate derived from crater counts.

The researchers estimate that the porous surface would reduce by a factor of three the size of craters on Ina's mounds. In other words, an impactor that would make a 100-foot-diameter crater in lunar basalt bedrock would make a crater of a little over 30 feet in a foam deposit. Taking that scaling relationship into account, the team gets a revised age for the Ina mounds of about 3.5 billion year old. That's similar to the surface age of the volcanic shield that surrounds Ina, and places the Ina activity within the timeframe of common volcanism on the Moon.

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