Found 229 Resources containing: Lemur
The surface of Europa, one of Jupiter’s four moons, makes a formidable foe. First off, it's wrapped in a thick rind of ice, torn open into great chasms by Jupiter’s massive gravitational pull. Then there’s the extremely low surface gravity and sheer, slippery ice canyons. But beneath all that ice, Europa is also thought to have an ocean of liquid that might support life—making it a prime target for our next in-depth solar system exploration.
So how will NASA overcome this treacherous challenge? It certainly can’t send a wheeled rover like Sojourner, which made one giant leap for robotkind when it first traversed Mars’ Ares Valles in 1996. Instead, NASA is looking to do away with those once-revolutionary wheels and reimagine how the next generation of robots will explore asteroids and the frigid outer worlds of the Solar System in the next few decades.
Currently weighing in at around 75 pounds, this next-gen rover is a fraction of the size of Mars’ Curiosity, which checks in at nearly a ton. Its size alone stretches the boundaries of robotic ability—but if it’s ever deployed, it will need to do more than that. The pint-sized rover will have to withstand wildly extreme temperatures and magnetic conditions; navigate any surface; and do it long enough to gather meaningful data with some of the lightest, smartest space science instruments ever built.
Is it up to the task?Three generations of NASA’s Mars rovers from 1997 to 2012, photographed inside the Mars Yard at the Jet Propulsion Lab in Pasadena, Calif: flight spare for Sojourner (front), Mars Exploration Rover Project test rover (left) and Curiosity test rover (right). (NASA / JPL-Caltech)
Admittedly, the robotic LEMUR—an acronym for “limbed excursion mechanical utility robot”—isn’t as cute as the wide-eyed, fluffy tailed species popularized by Dreamworks’ Madagascar. Rather, the robot gets its name from the real mammal’s ambidexterity. Initially intended to be a repair robot for manned moon missions, the rover has been redesigned for microgravity exploration of the vertical and inverted surfaces of canyons and caves.
“[Lemurs] use both their hands and feet for mobility and manipulation,” explains Aaron Parness, extreme environment robotics group leader at NASA’s Jet Propulsion Laboratory (JPL). “Even though our robot doesn’t have distinct arms and legs, it’s similar to a monkey or lemur in that it can use its feet for doing things much more efficiently than humans can.”
To ensure that the robot can move around in even stranger environments than those found on Mars, Parness's group has created what might be called a “chimerobot”: a robot that draws upon the abilities of many different terrestrial animals. With its reaching limbs and paddle-like feet, LEMUR evokes a spider or starfish, using its appendages to creep and cling to sheer surfaces.
The robot’s four limbs are fitted with interchangeable circular “feet,” which can be swapped out for attachments with different functions, Swiss Army knife-style, to help it traverse a variety of surfaces. Rock-climbing feet feature a series of tiny, razor-sharp steel hooks, known as microspines, to grip the rough surfaces of rocks firmly enough for one foot to hold the entire robot’s weight. For smooth surfaces, such as the outer hulls of space stations or satellites, LEMUR adheres itself with gecko-like sticky feet.
Recently, researchers took one of LEMUR’s “hands” to Antarctica to test out a new and potentially crucial attachment: screw-like ice drills. When Parness and his team are ready to test their hardware, they “look for the toughest places we can find,” Parness said. “We have to strike the right balance between having the right environment, but also not being so remote that it’s crazy expensive and impossible to get the team there. Antarctica was on the very edge of that.”
To do so, they called upon Aaron Curtis, a geographer-turned-volcanologist-turned-roboticist who has spent several summers on the far southern continent, crawling around icy tunnels formed by Mount Erebus, Earth’s southernmost active volcano. With average summertime temperatures dipping to -22 degrees Fahrenheit, the volcano, the ice formations it creates, and its standing lava lake represent a fair proxy of conditions a legged rover might encounter on icy moons like Europa or Enceladus.Aaron Curtis traveled to Antarctica this past December, where he tested robots and instruments designed for icy worlds like Europa. (Nial Peters)
As a research associate with Mount Erebus Volcano Observatory for six of the last seven years, Curtis charted the topography of the ice surrounding the volcano. His particular interests were beneath the surface, in the caves and tunnels melted into the ice by gases escaping the volcano’s fissures. Finding places where the tunnels connected to the outside was sometimes as simple as finding a towering “ice chimney,” meters-high structures formed by escaping gas. Other times that meant finding cave entrances by dropping a snowmobile into an obscured hole in the ground by accident.
After spending four years mapping one cave in 3-D to observe its changes over time, Curtis found himself repeatedly running into the same challenges over and over. First, his team wasn't able to get to certain areas because they were too toxic for human exploration. Second, they feared that their human presence could be inadvertently contaminating the rare environment with introduced microbes. These two concerns led him to consider the utility of robotic explorers.
“If we had a robot that could get around on ice, we could explore microbially sensitive and gas-filled caves,” says Curtis. His own ice-bot tinkering ended up being a good fit for the work already underway on at JPL, which he joined as a roboticist last October.
Microspines, it turns out, tend to just shred ice instead of grip them, since the attachment is designed to squeeze the spines down onto the rock to gain purchase. So Curtis designed an attachment that used tiny drills to dig itself into an icy surface.
The original design became clogged with ice, Curtis says, so he turned to something human ice enthusiasts trust with their lives: off-the-shelf ice screws. They’re hollow, allowing ice to pass through instead of building up behind the drilling end, and would also allow LEMUR to produce and collect ice samples as it creeps slowly along.
The next ice-world tests will likely take place on the glaciers atop Mount Rainier in Washington—with the full LEMUR chassis and not just a disembodied foot attachment. But Parness said that the ability to test out sampling capabilities also underscores another key goal of the entire development process.
“With field testing, we’re always trying to hit two objectives: to demonstrate technologies for future use, but also to do meaningful science at that location,” he says. In other words, not only are LEMUR tests helping us to eventually understand cryovolcanoes on other bodies; “this benefits us on Earth as well," says Parness.LEMUR gets a workout in Aaron Parness' lab at JPL during a recent test run. (NASA / JPL-Caltech)
For more than 35 years, Penelope Boston has sought out microbial life and its indicators in extreme environments, such as in the sulfuric acid-soaked Cueva de Villa Luz in Tabasco, in Mexico. In her former role as director of cave and karst studies at New Mexico Institute of Mining and Technology, where she studied aging and erosion processes of subterranean caves and sinkholes, Boston directed Parness toward locations where his team and LEMUR could learn what to look for, and how to look for it.
“I’ve helped Aaron’s team understand what the subtle cues might be that could indicate possible microbial or mineral deposits of interest for LEMUR to inspect,” said Boston, who now leads NASA’s Astrobiology Institute, over email.
The menu of possibilities, she added, are patterns left behind in or on rock formations by biological processes, such as textures that show microorganisms have been at work transforming bedrock or mineral deposits. On Earth, such evidence exists in places like Lechugilla Cave in New Mexico, where bacteria that feed on sulfur, iron and manganese are thought to have played a role in shaping the caves and spectacular stone formations there.
Clues left behind by microbial life are usually not so obvious. But by testing out a variety of instruments on both living and fossilized microbial remains, robots like LEMUR can shed more light on how these microbes lived, shaped their environments, and died.
Part of the challenge is making sure the tools are small enough to be mobile. So in addition to testing out the hardware, Parness and his team have been working with university partners to develop miniaturized remote sensing and analysis instruments. The idea is that LEMUR could wear them on its belly or like a backpack, mapping a cave or terrain in 3D with lidar, to gas chromatography, to looking for organics and carbon-rich molecules with a tiny near-infrared spectrometer.
“[Aaron] Parness’s group is exploring the possibilities of endowing LEMUR with pattern recognition and machine learning to help her see like a human being,” Boston said. “Paleobiology can often be very fine-scale and subtle, and enhanced visual and interpretation capabilities that robots can bring to the table are potentially immensely powerful tools to help us see and understand paleobiology better.”Aaron Curtis, a postdoctoral scholar at JPL, atop Antarctica's Mt. Erebus, the southernmost active volcano on earth. (Dylan Taylor)
Under the proposed federal budget from the White House, funding for the Asteroid Redirect Mission—the program where LEMUR is most likely to be used—would be eliminated. However, Parness and his team have been directed to continue their work on LEMUR. At the end of 2017, Parness will be heading back to the Titus Canyon area of Death Valley, where he's tested LEMUR before, stopping by lava tubes in New Mexico in the summertime.
There, 500-million-year-old fossilized algae stand in as an analog for potential ancient remains elsewhere—but engineers must make sure LEMUR can see them. “If we’re trying to look for life on cliff walls of Mars or other planets, we should look for oldest traces of life on Earth and test our instruments there,” Parness says. “If we can’t detect life on our own planet, what gives us confidence that we’d be able to find it in an older, harsher sample?”
Take a walk on the wrong side of the rainforest in Laos, Vietnam or eastern Cambodia, and the traps are unavoidable. Hunters lay these snares by burying a wire under a layer of dirt and leaves, then attaching it to a tree bent towards the ground. When a thin bamboo strip gets bumped, it releases the tree and pulls the animal’s leg into the air, suspending it until bush meat hunters return for the slaughter.
But there isn’t just a single trap. “Blanket snaring is when the habitat is saturated with snares,” says Jan Kamler, the Southeast Asia leopard program coordinator for Panthera, a global wild cat conservation organization. Traps can be packed as densely as one per square yard in a roughly 100-square yard patch of rainforest—so thick that even some of the people Kamler works with have been snagged.
“Basically if any animal walks through that area, they have to walk through a snare at some point,” he says.
Last month, the first comprehensive study on global bush meat consumption found that 113 species in Southeast Asia have dwindled to precarious numbers, primarily due to bush meat hunting and trapping. But while this region may be one of the worst affected, the study, published in Royal Society Open Science, reports that bush meat hunting is driving many of the world’s mammals to the brink of extinction. “The large mammals are much more threatened than the small ones,” says William Ripple, a professor of ecology at Oregon State University and lead author of the study. “This is likely because there is more meat on large mammals.”
Ripple was studying the global decline of large carnivores when he realized that one of the problems was that predators compete for prey with humans. He and his coauthors went through the descriptions of 1,169 mammals listed as threatened with extinction on the International Union for Conservation of Nature’s database, and found 301 animals which listed as primarily at threat from hunting. These included species as varied as tree kangaroos, the armored pangolin—recently dubbed the world’s most hunted animal—and rhinos, which are hunted for their meat or for body parts which supposedly provide medicinal value.
“Our analysis is conservative,” Ripple adds. “These 301 species are the worst cases of declining mammal populations for which hunting and trapping are clearly identified as a major threat. If data for a species were missing or inconclusive, we didn't include it.”
The report is an important first step in synthesizing the literature from so many different places, says Christopher Golden, a research scientist at Harvard University who studies the impact of hunting on human health in the island country of Madagascar. Ripple found that primates are the most threatened group of animals, with some 126 species including lowland gorillas, chimpanzees, bonobos and lemurs making the list. The latter face many threats in Madagascar, an isolated nation known for its unique endemic flora and fauna, according to Golden.
Ripple’s study shows that Madagascar has 46 endemic species threatened by bush meat hunting and trapping, more than any other country. Golden says the problem is driven by poverty: Madagascar is one of the poorest countries in the world, with 59 percent of people classified as “extremely poor” according to the World Bank. Some hunting and trapping is merely for subsistence, but other forms are less sustainable, he says,—such as selling animals to the bush meat market. The most difficult problem to tackle may be taste preference: Believe it or not, people actually enjoy the taste of critically endangered black and white ruffed lemur.
Most hunters in Cambodia using blanket snaring are looking to sell to the bush meat market as well, primarily hunting pigs or deer, says Kamler. However, tigers and the rapidly disappearing Indochinese leopard also fetch a high price tag on the traditional medicine market, making them a welcome bycatch. “These large felids move over such a large area that if there’s blanket snaring going on within several pockets of your home range, they’re eventually going to step in a snare,” he says. “You’re going to wipe them all out that way.”Bush meat hunting can be driven by nutritional needs, as well as the medicinal and meat markets. Endangered animals for sale in Phonsavan, Laos. (travelib prime / Alamy )
Hunting and habitat destruction can create the devastating one-two punch that pushes animals towards extinction, says Ripple. Penetration roads cut through jungles for the purpose of logging can give hunters access to otherwise secluded areas. And modern technology like better guns and vehicles is giving poachers an extra advantage—although Kamler says that guns are the least of some of these animals’ problems. “Hunting with a gun is the most specific,” he says. “You have to see the animal, you have to see it well—you know exactly what you’re shooting at. With a snare, you set thousands and you catch whatever.”
Donald Waller, a professor of botany and environmental studies at the University of Wisconsin, says that Ripple’s report helps give a comprehensive picture of the global problem of bush meat hunting. “The empty forest syndrome is one of the hardest challenges we face in conservation,” he says. “It’s not enough to have a forest we can see from satellite and space.”
One region that is conspicuously absent from the statistics is North America and Europe. Instead, nearly all of the 301 species threatened with extinction from hunting for consumption are from developing countries. “In the developed world there’s commonly a lack of large carnivores because the humans have eradicated them,” Ripple explains. The results of his study suggests that if we don’t act fast, the rest of the world will follow suit.
But some parts of North America have there own problems, says Waller. Since most of the large predators have already been wiped out in many parts of the continent, there is unchecked population growth of the few large mammals that are left. “Deer are the only large mammal most people are likely to see. And yet overabundant deer are now causing great reductions in tree regeneration, big changes in plant community structure, probably increases in the incidences of diseases—tick-borne diseases in particular,” he says. To address the overabundant deer issue in North America, he believes it’s worth considering a study advocating for the return in some areas of allowing the commercial harvest of wild deer meat.
Unfortunately, these kinds of issues may be more challenging to solve in developing countries like Madagascar, says Golden. The island was only colonized around 3,000 years ago, and many of the species were naïve to humans before they arrived. “Mass extinctions followed after human arrival, and now many species are deeply threatened by human hunting,” he says. The problem is especially hard to solve when hunting bush meat is part of local palettes and traditions. “When that’s the case, it’s more difficult to tackle in terms of interventions or getting people away from eating bush meat, because it's not simple development or technical interventions that’s going to solve that,” Golden says.
Even if the goal is to allow humans to keep hunting the animals that help those in poverty sustain nutritious diets, places like Madagascar need stricter regulation and better enforcement, says Golden. Otherwise, the nutritional resource provided by the meat will dwindle rapidly. “There could be an increase of about 30 percent in the rate of anemia locally because they lose access to this really important type of animal food,” he says, adding that unsustainable hunting "is self-depleting their own nutritional resource.”
Part of the solution in Madagascar, at least, involves helping people to take better care of domesticated animals like chickens. Golden and other researchers are developing a vaccine for the Newcastle disease, which kills 60-90 percent of poultry seasonally in the island country. "This intervention provides animal source foods to local people that do not have a hefty environmental footprint," he says. "If we can increase productivity and reduce price, we could naturally wean locals away from bush meat as a food source."
Ripple and his coauthors say that part of the problem could be helped by giving local communities incentives to switch to protein-rich plant crops. International policy must be changed to put pressure on countries to curb the demand for bush meat and medicinal products from animals, and local communities must be empowered to “capture the benefits from wildlife conservation with legal user rights over wildlife,” according to the study.
Kamler, who was not involved in Ripple’s study, says it should be a wake-up call about the problems caused by snaring, particularly in Southeast Asia. He says that the individual hunting of wild pigs, for example, is sustainable because the mammals reproduce rapidly. The problem is with the indiscriminant techniques, like blanket snaring and electrified fences. “Until governments formally acknowledge this imminent threat to their wildlife, it will be business as usual and little will be done to address the extinction crisis caused by the ever-expanding bush meat trade,” Kamler says.
The National Zoological Park’s 23-year-old male red-ruffed lemur, Joven, enjoys a tasty St. Patrick’s Day frozen treat made of apples, pears, cucumbers, honeydew and diluted […]
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What happens when you unleash an acclaimed luxury goods photographer on hundreds of anatomical animal skeletons kept in museum collections?
If that photographer is Patrick Gries and the skeletons are those of Paris' Natural Museum of History, you'll get a series of 300 stark photographs that transform staid, ordinary scientific specimens into biological art.
Gries shot these images to accompany text by oceanographer and documentarian Jean-Baptiste de Panafieu in the book Evolution, published by Xavier Barral, and they were recently featured in the Photovisa festival in Krasnodar, Russia.
"If you go to the museum, you'll see thousands of skeletons," Gries says. "My job was to take one specimen, isolate it, and work with light to photograph that specimen as if it was a sculpture."
De Panafieu's essays tell the story of evolution piece by piece—with chapters on adaptation, convergence, homology and other broad themes—while Gries' striking photos isolate the essence of each animal's unique adaptations.
Simultaneously, though, the photos highlight the common anatomical characteristics shared by all vertebrates. Stripped of fur and flesh, it can be hard to identify the skeletons without a label: without ears, a rabbit doesn't look all that different than a cheetah, and a monkey's skull differs only in scale from a human's.
Creating the seemingly simple images was far harder than it might appear, Gries says. The photos were taken over the course of six months, with animals selected largely by de Panafieu so that Gries could illustrate his essays. Most were from the Paris museum, but the duo also visited four other museum collections in France to obtain access to the skeletons they wanted.
Although the skeletons may appear to hover in a pristine state in midair, that illusion is the result of both digital and real-world ingenuity by Gries.
"It was very difficult working in the museums," he says. "Many of the skeletons' feet are nailed to wooden boards, and we couldn't touch anything, so we had to remove these things by computer."
Making the animals appear as though they were moving, as de Panafieu wanted for the book, was also rather tricky. "You have to realize that with the skeletons, nothing moves. Some of them look like they're in action, but everything is pretty stiff," Gries says. "So we had to use nails and wires to hold them in place."
"When you look at the pictures, it looks high tech, but the way we had to do it was quite low tech," he says.
"What I like about it is that you wouldn't even realize it," Gries says. "You'd look at the pictures and think they're just the way the skeletons are presented, not wondering, 'where are the nails and the wires?'"
The photos that include multiple animal skeletons, which illustrate concepts like predation or evolutionary arms races, are largely composed of pairs of animals that are featured together in the actual museum exhibits.
"What's most interesting to me is the cross between art and science. I love working on projects where I can cross disciplines," Gries says.
Although projects that encompass both art and science aren't radical ideas in the U.S. and in many other countries, Gries notes that there's still resistance to combining the two in France.
"I think that's starting to change, though, and I'm glad," he says. "I'm not a scientist, but I learned so much during this project, due to the chance I had to work with one."
During the winter, time slows down. You may find yourself curling up with your Netflix for hours, sleeping for half the day, or staying indoors for unhealthy periods of time. While doing so, you may wonder: why not just go all out, skip the unpleasantness and spend the whole winter unconscious in a warm, cozy burrow?
Researchers who hope to prepare humans for extended space travel have the same thought. They want to know: Why don’t humans hibernate—and could they in the future?
To answer that question, first we have to understand exactly what hibernation is. Here's what we know: Hibernation is when an animal goes into a state of extended inactivity. Often hiding itself away from the elements and predators, the animal's metabolism will slow to less than a quarter of its normal rate. This cools the creature's body and slows its heartbeat to just a few times per minute, for up to months at a time.
"They turn down the pilot light really," says Kelly Drew, a neuropharmacologist at the University of Alaska Fairbanks who studies the brains of hibernating Arctic ground squirrels. Hibernation is often stimulated by harsh conditions, shorter days or colder temperatures, which drive an animal to begin putting on fat and otherwise preparing to hibernate. The creature will then stay in this period of inactivity until it gets the right signal—light or temperature—to stir from its torpor.
Yet many misconceptions surround this powerful adaptation. For one, although hibernation resembles a deep sleep, it is not thought to be related to sleep at all. In fact, it may actually leave animals with a sleep-debt after they awaken from it, Drew says. "Hibernation is really energy conservation," she says. "It's an adaptation to resource limitation." Much like migration for birds, hibernation evolved to allow animals to make it through periods of extreme hardship.
"Some animals leave, some animals hibernate, and some animals just live with it," Drew says. (This explains why animals in zoos don't hibernate: A creature with plentiful food, water and shelter will have no need to undergo the process.)
For another, we usually think of hibernation as being associated with winter, which is when animals like bears, squirrels and groundhogs will check out for several months. But hibernation is not exclusively a cold-weather behavior, Drew says. Reptiles, amphibians insects and even a few mammals, such as the Madagascan fat-tailed dwarf lemur, practice the warm-weather hibernation—known as aestivation—to avoid periods of drought or extreme temperatures by chilling out underground.
Yet while researchers understand how hibernation could have evolved, surprisingly little is know about the actual process happens within the body. So far, scientists haven't found any unique genes in hibernating animals, for example. Furthermore, nobody knows what exactly is regulating those existing genes to allow the process of hibernation in some animals and not in others—like humans, for instance.
“We don’t even know which gene expression is necessary to hibernate,” Drew says.Jim Preston awakens a fellow traveler from hibernation in the film "Passengers." In the film, humans hibernate to survive the 120-year journey to another planet. (Columbia Pictures)
This mystery has just become more urgent as humans attempt the first manned mission to Mars. The idea of “deep sleep”—once the purview of deep space sci-fi films like Alien and now Passengers—is now a real possibility for scientists who want to ensure that human astronauts can survive during a months- or even yearslong journeys to other planets. One of those scientists is Drew, who is consulting with a company called Spaceworks Enterprises on a NASA-funded project to put humans into hibernation for spaceflight.
There are no known cases of natural human hibernation, according to Drew. But she has heard anecdotes about hibernation-like experiences in her research, including the practice of "lotska," in which Russian peasants a century ago would supposedly endure the harsh winter by awaking only once per day for 6 months to consume a small amount of bread and ale. Harvard University cardiologist Herbert Benson has also chronicled Buddhist monks who were able to lower their metabolism by 64 percent through certain meditation techniques.
Currently, however, Spaceworks is looking into techniques already being used in medicine, namely therapeutic hypothermia. First used medically more than 70 years ago, this technique involves cooling a person's body to near the freezing point of water (32 degrees F) to slow their cellular and brain functions. This technique can protect a patient's tissues from damage due to lack of oxygen or blood, usually after a heart attack or surgery such as a heart transplant. (Note: this should not be confused with the trend of cryotherapy, which has little scientific backing and has been linked to several deaths.)
While therapeutic hypothermia is usually used for periods of a day or two, Spaceworks president John Bradford notes that a woman in China was kept chilled for two weeks to allow her brain to heal from a traumatic injury. She recovered fully and returned to her daily life. But no other use of therapeutic hypothermia at that length or longer has been recorded, so it remains unclear how long the technique can be used safely.
Bradford envisions putting people into weeks-long increments of hibernation using body and brain-cooling techniques similar to therapeutic hypothermia to conserve space and resources for large-scale trips to Mars. "It's closer to reality than it sounds, but there's still a lot of questions, and a lot of development that needs to occur," Bradford told Popular Science about the project in December.
Yet there are still several hurdles to overcome, Drew points out. Hibernation isn’t simply a matter of turning the knob on your metabolism; it involves a host of other related adapations. Foremost among these is waste management. Animals that hibernate are able to essentially halt their urination and defecation during hibernation, Drew says, sometimes through a process of reabsorption to preserve nutrients. Unfortunately, humans can’t do this, though Drew has heard of proposals such as using rectal catheters.
And even if we figure out the poo problem, there are other challenges. Body temperatures below 37 degree Fahrenheit tend to disrupt the human digestive tract and may cause pain. Cold temperatures can also suppress the immune system, making people more vulnerable to infections. It may turn out that humans simply weren’t meant for hibernation.
On the less scientific side, the human in question would have to agree to hibernation—which may not be an appealing option. Putting oneself into a vulnerable state of hibernation and missing out on weeks or months of your life is something many people might be hesitant to choose. Bradford recounted to Inverse magazine that astronaut Buzz Aldrin objected at a conference presentation to the idea of hibernating, because he wouldn't want to miss out on the journey there.
However, Bradford thinks that practical concerns will eventually win out. “If it means the difference between being able to go to Mars, and not,” says Bradford, “I think everybody will do it.”
If scientists can make it possible for humans to hibernate during spaceflight, it will certainly be a great achievement. But perhaps the most amazing thing about hibernation is that humans have learned to survive without it—in environments as harsh as the Arctic and the tundra—for millennia. From adapting our diets to building igloos to wearing animal skins, Arctic communities have more than compensated for our inability to enter a winter-long torpor. So while we may marvel at bears and doormice, give us some credit, too.
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More than 2,000 years ago, a man died defending his family. For Mark Allen, it was a haunting reminder of how the struggle for resources can drive humanity to some of their darkest impulses.
The professor of anthropology at California State Polytechnic University, Pomona was reading through old accounts of the hasty salvage archaeology operation conducted on a site in an Oakland, California, suburb as it was dug up to make way for a paint factory in the 1920s. Archaeologists described hundreds of burials, but the story that most stood out to Allen was that of a middle-aged man whose bones were pierced at least four times by obsidian blades. The skeleton still had an obsidian blade in his hand. The bodies of three children and another man lay around him, also pierced.
"There's a lot of important information about this site, but one of those pieces is this guy who went down fighting trying to protect his family and failed," Allen says. The story in part inspired him to examine the causes of lethal violence among hunter-gatherers over the past two millennia in central California. Last month, he published a study on the cause of violent death in the Proceedings of the National Academy of Sciences.
"This study suggests that a key predictor in why humans would resort to violence is resource scarcity," Allen says.
The vexing question of how human violence originated has long provoked debate among anthropologists. Researchers are divided over questions like whether warfare was always with us or whether humans were initially peaceful, becoming more violent only as they became more organized. A 10,000-year old massacre recently discovered in Africa, for instance, reopened the dispute over how bellicose our hunter-gatherer ancestors truly were.
A survey of violence in the mammal world published in Nature in September found rates of violence in humans compared closely to evolutionary cousins like monkeys, lemurs and apes. Yet while humans may be only average-murdery among primates, that still makes them pretty violent toward each other: Primates are by far the most murderous mammalian group. The study suggested that we have a predilection for killing that has somewhat slackened as we became more organized.
To approach this longstanding problem, Allen and his coauthors needed a lot of data. They found it in the form of a massive database compiled from records of indigenous burials in central California excavated since 1975. Of the roughly 16,000 burials recorded over the past 5,000 years in the database, around 7.4 percent of the males and 4.5 percent of the females showed evidence of injuries from things like sharp blades, spears or arrow tips.
This was key: sharp-force trauma wounds, the researchers believed, were the best indicator of human-on-human violence. (Blunt force trauma could have been caused by falling, or even could have happened to the bones after burial.) Death by pointy objects, it seems, “is common throughout California's history," says Allen, who also wrote about the Oakland site in a chapter of the book Contemporary Issues in California Archaeology.
In the mid-1700s, California was one of the densest parts of North America above the Mexican border. The region boasted an estimated 300,000 people, compared to a total of 1 million across what is now Canada and the U.S. Many were concentrated in central California, partly due to the fact that it was a very productive environment, Allen says.
Groups of hunter-gatherers subsisted on salmon and birds, deer and other animals attracted to the water, and extracted flour from an abundant supply of acorns to last them through the winter. "[The area] could support a large population of hunter-gatherers," Allen says, "but that doesn't mean it was paradise."
To figure out the relative productivity of the area, the researchers turned to modern-day NASA satellite maps showing biomass, or the complete mass of biological material in a given area. Biomass, they write in the paper, demonstrates the abundance of food as well as the material available for hunter-gatherers to make tools. By comparing biomass and drought data to the burial evidence, Allen and team found that sharp-force trauma violence broke out more often when resources were low.
"That supports a long-standing hypothesis that resources scarcity would be the main predictor of the origins of violence and warfare in small-scale groups," he says.
Yet other researchers caution that merely measuring biomass is not a specific enough way to indicate available food. Net productivity in biomass might not always be the same thing as the availability of resources; it can also include, say, tree trunks, microbes and poisonous frogs. In the Amazon jungle, for example, there is a high amount of biomass, but there isn't always much for humans to eat.
The study “kind of raises my eyebrows a lot," says Raymond Hames, a professor of anthropology at the University of Nebraska who was not involved in the study.
Allen and team also examined the social and political complexity of the groups. They divided the burials into 19 different cultural groups with different levels of social complexity, based on other evidence found by the remains and Spanish accounts from missionary period. Organization levels varied from societies that had a single leader with informal councils of elders to those with powerful theocratic secret societies rather than secular leaders.
Yet none of these factors seemed to have any more influence on the number of people who'd been injured by piercing objects than resource availability. "[Groups with more command and control] don’t show more evidence of violence," Allen says.
While Hames appreciates the study's attention to causes of variation in violence rates, he questions the assumptions that political complexity remained consistent over the time period. "What guarantee do we have that that data reflects political complexity of 1,000 years ago?" he says.
Michael Blake, the head of the anthropology department at the University of British Columbia, questions the study's sample size, saying it isn't large enough to discount the possibility that political complexity may play a part leveraging violence. Blake points out that, while 19 different cultural groups were examined, the majority of these sit in the middle range of social organization, with only a couple outliers on the low or high ranges.
“I think it’s a really great idea as far as it goes,” Blake says. The solution, he adds, would be to examine a wider range of societies along the Pacific coast to see if the results still rang true.
For Lawrence Keeley, an anthropologist and author of the book War Before Civilization, any attempt ot examine the relationship between war and political or social complexity is futile. He says Allen's study crushes the concept of the myth of the pacified past, but is concerned that the argument that resource scarcity drives violence levels is too simplistic. "Humans are not passive subjects of their environments, but planners and anticipators," he points out.
Die Osteologie und Myologie von Sciurus vulgaris L., verglichen mit der Anatomie der Lemuriden und des Chiromys und ueber die Stellung des letzteren im natürlichen Systeme, von C.K. Hoffmann und H. Weyenbergh Jr
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