Artificial intelligence may help scientists make spray-on solar cells

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Artificial Intelligence may be just the thing to accelerate spray-on solar cell technology, which could revolutionize how consumers use energy.

A research team at the University of Central Florida used Machine Learning, aka Artificial Intelligence to optimize the materials used to make perovskite solar cells (PSC). The Organic-Inorganic halide perovskites material used in PSC converts photovoltaic power into consumable energy.

These perovskites can be processed in solid or liquid state, offering a lot of flexibility. Imagine being able to spray or paint bridges, houses and skyscrapers with the material, which

Artificial intelligence may help scientists make spray-on solar cells
Artificial intelligence may help scientists make spray-on solar cells

would then capture light, turn it into energy and feed it into the electrical grid. Until now, the solar cell industry has relied on silicon because of its efficiency. But that’s old technology with limits. Using perovskites, however, has one big barrier. They are difficult to make in a usable and stable material. Scientists spend a lot of time trying to find just the right recipe to make them with all the benefits — flexibility, stability, efficiency and low cost. That’s where artificial intelligence comes in.

The team’s work is so promising that its findings are the cover story Dec. 13 in the Advanced Energy Materials journal.

The team reviewed more than 2,000 peer-reviewed publications about perovskites and collected more than 300 data points then fed into the AI system they created. The system was able to analyze the information and predict which perovskites recipe would work best.

“Our results demonstrate that machine learning tools can be used for crafting perovskite materials and investigating the physics behind developing highly efficient PSCs,” says Jayan Thomas, the study’s lead author and an associate professor at the Nano Science Technology Center with multiple affiliations. “This can be a guide to design new materials as evidenced by our experimental demonstration.”

If this model bears out, it means researchers could identify the best formula to create a world standard. Then spray-on solar cells may happen in our lifetime, the researchers say.

“This is a promising finding because we use data from real experiments to predict and obtain a similar trend from the theoretical calculation, which is new for PSCs. We also predicted the best recipe to make PSC with different bandgap perovskites,” says Thomas and his graduate student, Jinxin Li, who is the first author of this paper. “Perovskites have been a hot research topic for the past 10 years, but we think we really have something here that can move us forward.”

A soft robotic insect that survives being flattened by a fly swatter

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Imagine swarms of robotic insects moving around us as they perform various tasks. It might sound like science fiction, but it’s actually more plausible than you might think.

Researchers at EPFL’s School of Engineering have developed a soft robotic insect, propelled at 3 cm per second by artificial muscles.

A soft robotic insect that survives being flattened by a fly swatter
A soft robotic insect that survives being flattened by a fly swatter

The team developed two versions of this soft robot, dubbed DE Ansect. The first, tethered using ultra-thin wires, is exceptionally robust. It can be folded, hit with a fly swatter or squashed by a shoe without impacting its ability to move. The second is an untethered model that is fully wireless and autonomous, weighing less than 1 gram and carrying its battery and all electronic components on its back. This intelligent insect is equipped with a microcontroller for a brain and photodiodes as eyes, allowing it to recognize black and white patterns, enabling DE Ansect to follow any line drawn on the ground.

DE Ansect was developed by a team at EPFL’s Soft Transducers Laboratory (LMTS), working with the Integrated Actuators Laboratory (LAI) and colleagues from the University of Cergy-Pontoise, France. The research was published in Science Robotics.

Vibration propulsion

DEAnsect is equipped with dielectric elastomer actuators (DEAs), a type of hair-thin artificial muscle that propels it forward through vibrations. These DEAs are the main reason why the insect is so light and quick. They also enable it to move over different types of terrain, including undulating surfaces.

The artificial muscles consist of an elastomer membrane sandwiched between two soft electrodes. The electrodes are attracted to one another when a voltage is applied, compressing the membrane, which returns to its initial shape when the voltage is turned off. The insect has such muscles fitted to each of its three legs. Movement is generated by switching the voltage on and off very quickly — over 400 times per second.

The team used nano fabrication techniques to enable the artificial muscles to work at relatively low voltages, by reducing the thickness of the elastomer membrane and by developing soft, highly conductive electrodes only a few molecules thick. This clever design allowed the researchers to dramatically reduce the size of the power source. “DEAs generally operate at several kilo volts, which required a large power supply unit,” explains LMTS director Herbert Shea. “Our design enabled the robot, which itself weighs just 0.2 gram, to carry everything it needs on its back.” “This technique opens up new possibilities for the broad use of DEAs in robotics, for swarms of intelligent robotic insects, for inspection or remote repairs, or even for gaining a deeper understanding of insect colonies by sending a robot to live amongst them.”

“We’re currently working on an untethered and entirely soft version with Stanford University,” says Shea. “In the longer term, we plan to fit new sensors and emitters to the insects so they can communicate directly with one another.”

Tiny magnetic particles enable new material to bend, twist, and grab

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A team of researchers from the Georgia Institute of Technology and The Ohio State University has developed a soft polymer material, called magnetic shape memory polymer, that uses magnetic fields to transform into a variety of shapes. The material could enable a range of new applications from antennas that change frequencies on the fly to gripper arms for delicate or heavy objects.

Tiny magnetic particles enable new material to bend, twist, and grab
Tiny magnetic particles enable new material to bend, twist, and grab

The material is a mixture of three different ingredients, all with unique characteristics: two types of magnetic particles, one for inductive heat and one with strong magnetic attraction, and shape-memory polymers to help lock various shape changes into place.

“This is the first material that combines the strengths of all of these individual components into a single system capable of rapid and reprogrammable shape changes that are lockable and reversible,” said Jerry Qi, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech.

The research, which was reported Dec. 9 in the journal Advanced Materials, was sponsored by the National Foundation of Science, the Air Force Office of Scientific Research, and the Department of Energy.

To make the material, the researchers began by distributing particles of neodymium iron boron (NdFeB) and iron oxide into a mixture of shape memory polymers. Once the particles were fully incorporated, the researchers then molded that mixture into various objects designed to evaluate how the material performed in a series of applications.

Tiny magnetic particles enable new material
Tiny magnetic particles enable new material

For example, the team made a gripper claw from a t-shaped mold of the magnetic shape memory polymer mixture. Applying a high-frequency, oscillating magnetic field to the object caused the iron oxide particles to heat up through induction and warm the entire gripper. That temperature rise, in turn, caused the shape memory polymer matrix to soften and become pliable. A second magnetic field was then applied to the gripper, causing its claws to open and close. Once the shape memory polymers cool back down, they remain locked in that position.

The shape-changing process takes only a few seconds from start to finish, and the strength of the material at its locked state allowed the gripper to lift objects up to 1,000 times its own weight.

“We envision this material being useful for situations where a robotic arm would need to lift a very delicate object without damaging it, such as in the food industry or for chemical or biomedical applications,” Qi said.

The new material builds on earlier research that outlined actuation mechanisms for soft robotics and active materials and evaluated the limitations in current technologies.

“The degree of freedom is limited in conventional robotics” said Ruike (Renee) Zhao, an assistant professor in the Department of Mechanical and Aerospace Engineering at Ohio State. “With soft materials, that degree of freedom is unlimited.”

The researchers also tested other applications, where coil-shaped objects made from the new material expanded and retracted — simulating how an antenna could potentially change frequencies when actuated by the magnetic fields.

“This process requires us to use of magnetic fields only during the actuation phase,” Zhao said. “So, once an object has reached its new shape, it can be locked there without constantly consuming energy.”

Feeding 10 billion people by 2050 within planetary limits may be achievable

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A global shift towards healthy and more plant-based diets, halving food loss and waste, and improving farming practices and technologies are required to feed 10 billion people sustainably by 2050, a new study finds. Adopting these options reduces the risk of crossing global environmental limits related to climate change, the use of agricultural land, the extraction of freshwater resources, and the pollution of ecosystems through overapplication of fertilizers, according to the researchers.

The study,  is the first to quantify how food production and consumption affects the planetary boundaries that describe a safe operating space for humanity beyond which Earth’s vital systems could become unstable.

“No single solution is enough to avoid crossing planetary boundaries. But when the solutions are implemented together, our research indicates that it may be possible to feed the growing population sustainably,” says Dr Marco Springmann of the Oxford Martin Programme on the Future of Food and the Nuffield Department of Population Health at the University of Oxford, who led the study.

“Without concerted action, we found that the environmental impacts of the food system could increase by 50-90% by 2050 as a result of population growth and the rise of diets high in fats, sugars and meat. In that case, all planetary boundaries related to food production would be surpassed, some of them by more than twofold.”

The study, funded by EAT as part of the EAT-Lancet Commission for Food, Planet and Health and by Wellcome’s “Our Planet, Our Health” partnership on Livestock Environment and People, combined detailed environmental accounts with a model of the global food system that tracks the production and consumption of food across the world. With this model, the researchers analysed several options that could keep the food system within environmental limits. They found:

  • Climate change cannot be sufficiently mitigated without dietary changes towards more plant-based diets. Adopting more plant-based “flexitarian” diets globally could reduce greenhouse gas emissions by more than half, and also reduce other environmental impacts, such as fertilizer application and the use of cropland and freshwater, by a tenth to a quarter.
  • In addition to dietary changes, improving management practices and technologies in agriculture is required to limit pressures on agricultural land, freshwater extraction, and fertilizer use. Increasing agricultural yields from existing cropland, balancing application and recycling of fertilizers, and improving water management, could, along with other measures, reduce those impacts by around half.
  • Finally, halving food loss and waste is needed for keeping the food system within environmental limits. Halving food loss and waste could, if globally achieved, reduce environmental impacts by up to a sixth (16%).

“Many of the solutions we analysed are being implemented in some parts of the world, but it will need strong global co-ordination and rapid upscale to make their effects felt.”

“Improving farming technologies and management practices will require increasing investment in research and public infrastructure, the right incentive schemes for farmers, including support mechanisms to adopt best available practices, and better regulation, for example of fertilizer use and water quality,” says Line Gordon, executive director of the Stockholm Resilience Centre and an author on the report.

“Tackling food loss and waste will require measures across the entire food chain, from storage, and transport, over food packaging and labelling to changes in legislation and business behaviour that promote zero-waste supply chains.”

“When it comes to diets, comprehensive policy and business approaches are essential to make dietary changes towards healthy and more plant-based diets possible and attractive for a large number of people. Important aspects include school and workplace programmes, economic incentives and labelling, and aligning national dietary guidelines with the current scientific evidence on healthy eating and the environmental impacts of our diet,” adds Springmann.

Large-scale US wind power would cause warming that would take roughly a century to offset

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All large-scale energy systems have environmental impacts, and the ability to compare the impacts of renewable energy sources is an important step in planning a future without coal or gas power. Extracting energy from the wind causes climatic impacts that are small compared to current projections of 21st century warming, but large compared to the effect of reducing US electricity emissions to zero with solar. Research publishing in the journal Joule on October 4 reports the most accurate modelling yet of how increasing wind power would affect climate, finding that large-scale wind power generation would warm the Continental United States 0.24 degrees Celsius because wind turbines redistribute heat in the atmosphere.

“Wind beats coal by any environmental measure, but that doesn’t mean that its impacts are negligible,” says senior author David Keith, an engineering and public policy professor at Harvard University. “We must quickly transition away from fossil fuels to stop carbon emissions. In doing so, we must make choices between various low-carbon technologies, all of which have some social and environmental impacts.”

“Wind turbines generate electricity but also alter the atmospheric flow,” says first author Lee Miller. “Those effects redistribute heat and moisture in the atmosphere, which impacts climate. We attempted to model these effects on a continental scale.”

To compare the impacts of wind and solar, Keith and Miller started by establishing a baseline for the 2012-2014 US climate using a standard weather forecasting model. Then they added in the effect on the atmosphere of covering one third of the Continental US with enough wind turbines to meet present-day US electricity demand. This is a relevant scenario if wind power plays a major role in decarbonizing the energy system in the latter half of this century. This scenario would warm the surface temperature of the Continental US by 0.24 degrees Celsius.

Their analysis focused on the comparison of climate impacts and benefits. They found that it would take about a century to offset that effect with wind-related reductions in greenhouse gas concentrations. This timescale was roughly independent of the specific choice of total wind power generation in their scenarios.

“The direct climate impacts of wind power are instant, while the benefits accumulate slowly,” says Keith. “If your perspective is the next 10 years, wind power actually has — in some respects — more climate impact than coal or gas. If your perspective is the next thousand years, then wind power is enormously cleaner than coal or gas.”

More than ten previous studies have now observed local warming caused by US wind farms. Keith and Miller compared their simulated warming to observations and found rough consistency between the observations and model.

They also compared wind power’s impacts with previous projections of solar power’s influence on the climate. They found that, for the same energy generation rate, solar power’s impacts would be about 10 times smaller than wind. But both sources of energy have their pros and cons.

“In terms of temperature difference per unit of energy generation, solar power has about 10 times less impact than wind,” says Miller. “But there are other considerations. For example, solar farms are dense, whereas the land between wind turbines can be co-utilized for agriculture.” The density of wind turbines and the time of day during which they operate can also influence the climatic impacts.

Keith and Miller’s simulations do not consider any impacts on global-scale meteorology, so it remains somewhat uncertain how such a deployment of wind power may affect the climate in other countries.

“The work should not be seen as a fundamental critique of wind power. Some of wind’s climate impacts may be beneficial. So rather, the work should be seen as a first step in getting more serious about assessing these impacts,” says Keith. “Our hope is that our study, combined with the recent direct observations, marks a turning point where wind power’s climatic impacts begin to receive serious consideration in strategic decisions about decarbonizing the energy system.”


Viruses influenced gene sharing between Neanderthals and humans

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Human evolution used to be depicted as a straight line, gradually progressing from an ape-like ancestor to modern Homo sapiens. But thanks to next-generation sequencing — as well as the discovery of genetic material from extinct subspecies of early humans — findings in recent years have shown that it wasn’t quite so orderly. The human family tree is full of twists and branches that helped shape what we are today. Now, a study published in the journal Cell is reporting new details about the role of viruses in shaping evolution, in particular viral interactions between modern humans and Neanderthals.

“It’s not a stretch to imagine that when modern humans met up with Neanderthals, they infected each other with pathogens that came from their respective environments,” “By interbreeding with each other, they also passed along genetic adaptations to cope with some of those pathogens.”

Current thinking is that modern humans began moving out of Africa and into Eurasia about 70,000 years ago. When they arrived, they met up with Neanderthals who, along with their own ancestors, had been adapting to that geographic area for hundreds of thousands of years. The Eurasian environment shaped Neanderthals’ evolution, including the development of adaptations to viruses and other pathogens that were present there but not in Africa.

The Cell study provides new details about the role of adaptive introgression, or hybridization between species, in human evolution. “Some of the Neanderthals had adaptive mutations that gave them advantages against these pathogens, and they were able to pass some of these mutations on to modern humans,” explains Enard, who completed the work while he was a postdoctoral researcher at Stanford University. “That’s called positive natural selection — it favors certain individuals that carry these advantageous mutations.”

Their earlier research focused on how viruses impacted the evolution of humans. In 2016, they reported that about one-third of protein adaptations since humans split from other great apes was driven by a response to infectious viruses. The new work built on those findings looked at which of those adaptations may have come from Neanderthals.

In the current study, the investigators annotated thousands of genes in the human genome that are known to interact with pathogens — more than 4,000 of the 25,000 total genes. “We focused on these genes because the ones that interact with viruses are much more likely to have been involved in adaptation against infectious disease compared with genes that don’t have anything to do with viruses.”

They then looked at whether there was an enrichment of stretches of Neanderthal DNA in those 4,000 genes. Earlier studies from other groups have shown that Neanderthal DNA is present in humans. Those sequences are publicly available to investigators in the field. Based on the analysis, Enard and Petrov found strong evidence that adaptive genes that provided resistance against viruses were shared between Neanderthals and modern humans.

“Many Neanderthal sequences have been lost in modern humans, but some stayed and appear to have quickly increased to high frequencies at the time of contact, suggestive of their selective benefits at that time,” Petrov says. “Our research aims to understand why that was the case. We believe that resistance to specific RNA viruses provided by these Neanderthal sequences was likely a big part of the reason for their selective benefits.”

“One of the things that population geneticists have wondered about is why we have maintained these stretches of Neanderthal DNA in our own genomes,” Enard adds. “This study suggests that one of the roles of those genes was to provide us with some protection against pathogens as we moved into new environments.”


New color-generation mechanism discovered in ‘rainbow’ weevil

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Researchers from Yale-NUS College and the University of Fribourg in Switzerland have discovered a novel colour-generation mechanism in nature, which if harnessed, has the potential to create cosmetics and paints with purer and more vivid hues, screen displays that project the same true image when viewed from any angle, and even reduce the signal loss in optical fibres.  Dr Saranathan examined the rainbow-coloured patterns in the elytra (wing casings) of a snout weevil from the Philippines, Pachyrrhynchus congestus pavonius, using high-energy X-rays, while Dr Wilts performed detailed scanning electron microscopy and optical modelling. They discovered that to produce the rainbow palette of colours, the weevil utilised a colour-generation mechanism that is so far found only in squid, cuttlefish, and octopuses, which are renowned for their colour-shifting camouflage. The study was published in the peer-reviewed journal Small.

P. c. pavonius, or the “Rainbow” Weevil, is distinctive for its rainbow-coloured spots on its thorax and elytra. These spots are made up of nearly-circular scales arranged in concentric rings of different hues, ranging from blue in the centre to red at the outside, just like a rainbow. While many insects have the ability to produce one or two colours, it is rare that a single insect can produce such a vast spectrum of colours. Researchers are interested to figure out the mechanism behind the natural formation of these colour-generating structures, as current technology is unable to synthesise structures of this size.

“The ultimate aim of research in this field is to figure out how the weevil self-assembles these structures, because with our current technology we are unable to do so,” Dr Saranathan said. “The ability to produce these structures, which are able to provide a high colour fidelity regardless of the angle you view it from, will have applications in any industry which deals with colour production. We can use these structures in cosmetics and other pigmentations to ensure high-fidelity hues, or in digital displays in your phone or tablet which will allow you to view it from any angle and see the same true image without any colour distortion. We can even use them to make reflective cladding for optical fibres to minimise signal loss during transmission.”

Dr Saranathan and Dr Wilts examined these scales to determine that the scales were composed of a three-dimensional crystalline structure made from chitin (the main ingredient in insect exoskeletons). They discovered that the vibrant rainbow colours on this weevil’s scales are determined by two factors: the size of the crystal structure which makes up each scale, as well as the volume of chitin used to make up the crystal structure. Larger scales have a larger crystalline structure and use a larger volume of chitin to reflect red light; smaller scales have a smaller crystalline structure and use a smaller volume of chitin to reflect blue light. According to Dr Saranathan, who previously examined over 100 species of insects and spiders and catalogued their colour-generation mechanisms, this ability to simultaneously control both size and volume factors to fine-tune the colour produced has never before been shown in insects, and given its complexity, is quite remarkable. “It is different from the usual strategy employed by nature to produce various different hues on the same animal, where the chitin structures are of fixed size and volume, and different colours are generated by orienting the structure at different angles, which reflects different wavelengths of light,” Dr Saranathan explained.

We may hear others’ footsteps, but how do we ignore our own?

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A team of scientists has uncovered the neural processes mice use to ignore their own footsteps, a discovery that offers new insights into how we learn to speak and play music.

“The ability to ignore one’s own footsteps requires the brain to store and recall memories and to make some pretty stellar computations,” explains David Schneider, an assistant professor at New York University’s Center for Neural Science and one of the paper’s lead authors. “These are the building blocks for other, more important sound-generating behaviors, like recognizing the sounds you make when learning how to speak or to play a musical instrument.”

The research, centered on an intuition — that we are usually unaware of the sound of our own footsteps — as a vehicle for understanding larger neural phenomena: how this behavior reveals the ability to monitor, recognize, and remember the sound of one’s own movements in relation to those of their larger environments.

“The capacity to anticipate and discriminate these movement-related sounds from environmental sounds is critical to normal hearing,” Schneider explains. “But how the brain learns to anticipate the sounds resulting from our movements remains largely unknown.”

To explore this, Schneider and his colleagues, designed an “acoustic virtual reality system” for the mice. Here, the scientists controlled the sounds the mice made walking on a treadmill while monitoring the animals’ neural activity, allowing them to identify the neural circuit mechanisms that learn to suppress movement-related sounds.

Overall, they found a flexibility in neural function — the mice developed an adjustable “sensory filter” that allowed them to ignore the sounds of their own footsteps. In turn, this allowed them to better detect other sounds arising from their surroundings.

“For mice, this is really important,” said Schneider. “They are prey animals, so they really need to be able to listen for a cat creeping up on them, even when they’re walking and making noise.”

Being able to ignore the sounds of one’s own movements is likely important for humans as well. But the ability to anticipate the sounds of our actions is also important for more complex human behaviors such as speaking or playing music.

“When we learn to speak or to play music, we predict what sounds we’re going to hear — such as when we prepare to strike keys on a piano — and we compare this to what we actually hear,” explains Schneider. “We use mismatches between expectation and experience to change how we play — and we get better over time because our brain is trying to minimize these errors.”

Being unable to make predictions like this is also thought to be involved in a spectrum of afflictions.

“Overactive prediction circuits in the brain are thought to lead to the voice-like hallucinations associated with schizophrenia while an inability to learn the consequences of one’s actions could lead to debilitating social paralysis, as in autism,” explains Schneider. “By figuring out how the brain normally makes predictions about self-generated sounds, we open the opportunity for understanding a fascinating ability — predicting the future — and for deepening our understanding of how the brain breaks during disease.”

Falling stars hold clue for understanding dying stars

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An international team of researchers has proposed a new method to investigate the inner workings of supernovae explosions. This new method uses meteorites and is unique in that it can determine the contribution from electron anti-neutrinos, enigmatic particles which can’t be tracked through other means.

Supernovae are important events in the evolution of stars and galaxies, but the details of how the explosions occur are still unknown. By measuring the amount of 98Ru (an isotope of Ruthenium) in meteorites, it should be possible to estimate how much of its progenitor 98Tc (a short-lived isotope of Technetium) was present in the material from which the Solar System formed. The amount of 98Tc in turn is sensitive to the characteristics, such as temperature, of electron anti-neutrinos in the supernova process; as well as to how much time passed between the supernova and the formation of the Solar System. The expected traces of 98Tc are only a little below the smallest currently detectable levels, raising hopes that they will be measured in the near future.

“There are six neutrino species. Previous studies have shown that neutrino-isotopes are predominantly produced by the five neutrino species other than the electron anti-neutrino. By finding a neutrino-isotope synthesized predominantly by the electron anti-neutrino, we can estimate the temperatures of all six neutrino species, which are important for understanding the supernova explosion mechanism.”

At the end of its life, a massive star dies in a fiery explosion known as a supernova. This explosion blasts most of the mass in the star out into outer space. That mass is then recycled into new stars and planets, leaving distinct chemical signatures which tell scientists about the supernova. Meteorites, sometimes called falling stars, formed from material left over from the birth of the Solar System, thus preserving the original chemical signatures.

Massive monumental cemetery built by Eastern Africa’s earliest herders discovered in Kenya

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An international team, including researchers at Stony Brook University and the Max Planck Institute for the Science of Human History, has found the earliest and largest monumental cemetery in eastern Africa. The Lothagam North Pillar Site was built 5,000 years ago by early pastoralists living around Lake Turkana, Kenya. This group is believed to have had an egalitarian society, without a stratified social hierarchy. Thus their construction of such a large public project contradicts long-standing narratives about early complex societies, which suggest that a stratified social structure is necessary to enable the construction of large public buildings or monuments.

The Lothagam North Pillar Site was a communal cemetery constructed and used over a period of several centuries, between about 5,000 and 4,300 years ago. Early herders built a platform approximately 30 meters in diameter and excavated a large cavity in the center to bury their dead. After the cavity was filled and capped with stones, the builders placed large, megalith pillars, some sourced from as much as a kilometer away, on top. Stone circles and cairns were added nearby. An estimated minimum of 580 individuals were densely buried within the central platform cavity of the site. Men, women, and children of different ages, from infants to the elderly, were all buried in the same area, without any particular burials being singled out with special treatment. Additionally, essentially all individuals were buried with personal ornaments and the distribution of ornaments was approximately equal throughout the cemetery. These factors indicate a relatively egalitarian society without strong social stratification.

Historically, archeologists have theorized that people built permanent monuments as reminders of shared history, ideals and culture, when they had established a settled, socially stratified agriculture society with abundant resources and strong leadership. It was believed that a political structure and the resources for specialization were prerequisites to engaging in monument building. Ancient monuments have thus previously been regarded as reliable indicators of complex societies with differentiated social classes. However, the Lothagam North cemetery was constructed by mobile pastoralists who show no evidence of a rigid social hierarchy. “This discovery challenges earlier ideas about monumentality,” explains Elizabeth Sawchuk of Stony Brook University and the Max Planck Institute for the Science of Human History. “Absent other evidence, Lothagam North provides an example of monumentality that is not demonstrably linked to the emergence of hierarchy, forcing us to consider other narratives of social change.”

The discovery is consistent with similar examples elsewhere in Africa and on other continents in which large, monumental structures have been built by groups thought to be egalitarian in their social organization. This research has the potential to reshape global perspectives on how — and why — large groups of people come together to form complex societies. In this case, it appears that Lothagam North was built during a period of profound change. Pastoralism had just been introduced to the Turkana Basin and newcomers arriving with sheep, goats, and cattle would have encountered diverse groups of fisher-hunter-gatherers already living around the lake. Additionally, newcomers and locals faced a difficult environmental situation, as annual rainfall decreased during this period and Lake Turkana shrunk by as much as fifty percent. Early herders may have constructed the cemetery as a place for people to come together to form and maintain social networks to cope with major economic and environmental change.

“The monuments may have served as a place for people to congregate, renew social ties, and reinforce community identity,” states Anneke Janzen also of the Max Planck Institute for the Science of Human History. “Information exchange and interaction through shared ritual may have helped mobile herders navigate a rapidly changing physical landscape.” After several centuries, pastoralism became entrenched and lake levels stabilized. It was around this time that the cemetery ceased to be used.

“The Lothagam North Pillar Site is the earliest known monumental site in eastern Africa, built by the region’s first herders,” states Hildebrand. “This finding makes us reconsider how we define social complexity, and the kinds of motives that lead groups of people to create public architecture.”