A star like a Matryoshka doll: New theory for gravastars

If gravitational condensate stars (or gravastars) actually existed, they would look similar to black holes to a distant observer. Two theoretical physicists at Goethe University Frankfurt have now found a new solution to Albert Einstein's theory of general relativity, according to which gravitational stars could be structured like a Russian matryoshka doll, with one gravastar located inside another.

The interior of black holes remains a conundrum for science.

In 1916, German physicist Karl Schwarzschild outlined a solution to Albert Einstein's equations of general relativity, according to which the center of a black hole consists of a so-called singularity, a point at which space and time no longer exist.

Here, the theory goes, all physical laws, including Einstein's general theory of relativity, no longer apply; the principle of causality is suspended.

This constitutes a great nuisance for science: after all, it means that no information can escape from a black hole beyond the so-called event horizon.

This could be a reason why Schwarzschild's solution did not attract much attention outside the theoretical realm for a long time -- that is, until the first candidate for a black hole was discovered in 1971, followed by the discovery of the black hole in the center of our Milky Way in the 2000s, and finally the first image of a black hole, captured by the Event Horizon Telescope Collaboration in 2019.

In 2001, Pawel Mazur and Emil Mottola proposed a different solution to Einstein's field equations that led to objects which they called gravitational condensate stars, or gravastars.

Contrary to black holes, gravastars have several advantages from a theoretical astrophysics perspective.

On the one hand, they are almost as compact as black holes and also exhibit a gravity at their surface that is essentially as strong as that of a black hole, hence resembling a black hole for all practical purposes.

On the other hand, gravastars do not have an event horizon, that is, a boundary from within which no information can be sent out, and their core does not contain a singularity.

Instead, the center of gravastars is made up of an exotic -- dark -- energy that exerts a negative pressure to the enormous gravitational force compressing the star.

The surface of gravastars is represented by a wafer-thin skin of ordinary matter, the thickness of which approaches zero.

Theoretical physicists Daniel Jampolski and Prof. Luciano Rezzolla of Goethe University Frankfurt have now presented a solution to the field equations of general relativity that describes the existence of a gravastar inside another gravastar.

They have given this hypothetical celestial object the name "nestar" (from the English "nested").

Daniel Jampolski, who discovered the solution as part of his Bachelor's thesis supervised by Luciano Rezzolla, says: "The nestar is like a matryoshka doll," adding that, "our solution to the field equations allows for a whole series of nested gravastars." Whereas Mazur and Mottola posit that the gravastar has a near infinite thin skin consisting of normal matter, the nestar's matter-composed shell is somewhat thicker: "It's a little easier to imagine that something like this could exist."

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Early-stage subduction invasion

Our planet's lithosphere is broken into several tectonic plates. Their configuration is ever-shifting, as supercontinents are assembled and broken up, and oceans form, grow, and then start to close in what is known as the Wilson cycle.

In the Wilson cycle, when a supercontinent like Pangea is broken up, an interior ocean is formed.

In the case of Pangea, the interior ocean is the Atlantic. This ocean has a rift in the middle, and passive margins on the side, which means no seismic or volcanic activity occurs along its shores.

Destined to keep expanding, an Atlantic-type ocean will eventually become the exterior ocean of the next supercontinent.

Currently, Earth's exterior ocean is the Pacific. The Pacific also has a rift in the middle, but it is bounded by subduction zones and thus will eventually close.

Along its margins, earthquakes and eruptions abound -- a pattern known as the ring of fire.

The ocean-closing phase of each Wilson cycle requires the transition from passive to active (subducting) margins at the edges of the interior ocean.

The oceanic crust along the coast of the Atlantic is old and heavy, so it is primed to subduct, but before it can do so, it must break and bend.

The only force in nature that can break oceanic plates like these is slab pull from another subduction zone.

But this doesn't happen spontaneously. So how does subduction initiate around interior oceans?

There currently are two subduction zones in the Atlantic: the Lesser Antilles and Scotia.

But neither of them formed spontaneously in the Atlantic; they were forced by subduction zones in the Pacific during the Cretaceous and then propagated along transform margins, where the continent is narrow and there is barely a land bridge.

They jumped oceans.

Today, on the eastern shore of the Atlantic, in Gibraltar, we have the opportunity to observe the very earliest stages of this process, known as subduction invasion, while the jump occurs from a different basin -- in this case, the Mediterranean.

This is an incredibly valuable opportunity because the chances of observing the very start of any given tectonic process are limited.

And subduction initiation is difficult to observe because it leaves almost no traces behind.

Once subduction starts, it erases the record of its initial stages; the subducted plate ends up in the mantle, never to be exposed at the surface again (except in the rare case of ophiolites).

The activity of the Gibraltar subduction zone in the Mediterranean has been hotly debated.

The Gibraltar arc formed in the Oligocene as a part of the Western Mediterranean subduction zones.

While we can see a subducted plate in the mantle underneath it, almost no further movement is currently happening.

A new paper by Duarte et al., just published in Geology, suggests that Gibraltar is active -- it is just currently experiencing a slow movement phase because the subducting slab is very narrow, and it is trying to pull down the entire Atlantic plate.

"[These are] some of the oldest pieces of crust on Earth, super strong and rigid -- if it were any younger, the subducting plate would just break off and subduction would come to a halt," explains Duarte.

"Still, it is just barely strong enough to make it, and thus moves very slowly."

A new computational, gravity-driven 3-D model, developed by the authors, shows that this slow phase will last for another 20 million years.

After that, the Gibraltar subduction zone will invade the Atlantic Ocean and accelerate.

That will be the beginning of the recycling of crust on the eastern side of the Atlantic, and might be the start of the Atlantic itself beginning to close, initiating a new phase in the Wilson cycle.

Broadly, this study shows that subduction invasion, the process whereby a new subduction zone forms in an exterior ocean and then migrates to an interior ocean, is likely a common mechanism of subduction initiation in Atlantic-type oceans, and thus plays a key role in the geological evolution of our planet.

Locally, the finding that the Gibraltar subduction is still currently active has important implications for seismic activity in the area.

Recurrence intervals are expected to be very long during this slow phase, but the potential for high-magnitude events, such as the 1755 Lisbon earthquake, remains and requires preparedness.

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Discovery of new Li ion conductor unlocks new direction for sustainable batteries

One of the grand challenges for materials science is the design and discovery of new materials that address global priorities such as Net Zero.

In a paper published in the journal Science, researchers at the University of Liverpool have discovered a solid material that rapidly conducts lithium ions.

Such lithium electrolytes are essential components in the rechargeable batteries that power electric vehicles and many electronic devices.

Consisting of non-toxic earth-abundant elements, the new material has high enough Li ion conductivity to replace the liquid electrolytes in current Li ion battery technology, improving safety and energy capacity.

Using a transformative scientific approach to design the material, the interdisciplinary research team from the University synthesised the material in the laboratory, determined its structure (the arrangement of the atoms in space) and demonstrated it in a battery cell.

The new material is one of a very small number of solid materials that achieve Li ion conductivity high enough to replace liquid electrolytes, and operates in a new way because of its structure.

Its discovery was achieved through a collaborative computational and experimental workflow that used AI and physics-based calculations to support decisions made by chemistry experts at the University.

The new material provides a platform for the optimisation of chemistry to further enhance the properties of the material itself, and to identify other materials based on the new understanding provided by the study.

Professor Matt Rosseinsky, from the University of Liverpool's Department of Chemistry, said: "This research demonstrates the design and discovery of a material that is both new and functional. The structure of this material changes previous understanding of what a high-performance solid-state electrolyte looks like.

"Specifically, solids with many different environments for the mobile ions can perform very well, not just the small number of solids where there is a very narrow range of ionic environments. This dramatically opens up the chemical space available for further discoveries.

Recent reports and media coverage herald the use of AI tools to find potentially new materials.

In these cases, the AI tools are working independently and thus are likely to recreate what they were trained on in various ways, generating materials that may be very similar to known ones.

"This discovery research paper shows that AI and computers marshalled by experts can tackle the complex problem of real-world materials discovery, where we seek meaningful differences in composition and structure whose impact on properties is assessed based on understanding."

"Our disruptive design approach offers a new route to discovery of these and other high-performance materials that rely on the fast motion of ions in solids."

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Evidence of geothermal activity within icy dwarf planets

A team co-led by Southwest Research Institute found evidence for hydrothermal or metamorphic activity within the icy dwarf planets Eris and Makemake, located in the Kuiper Belt. Methane detected on their surfaces has the tell-tale signs of warm or even hot geochemistry in their rocky cores, which is markedly different than the signature of methane from a comet.

"We see some interesting signs of hot times in cool places," said SwRI's Dr. Christopher Glein, an expert in planetary geochemistry and lead author of a paper about this discovery.

The Kuiper Belt is a vast donut-shaped region of icy bodies beyond the orbit of Neptune at the edge of the solar system.

Eris and Makemake are comparable in size to Pluto and its moon Charon.

These bodies likely formed early in the history of our solar system, about 4.5 billion years ago.

Far from the heat of our Sun, KBOs were believed to be cold, dead objects.

Newly published work from JWST studies made the first observations of isotopic molecules on the surfaces of Eris and Makemake.

These so-called isotopologues are molecules that contain atoms having a different number of neutrons.

They provide data that are useful in understanding planetary evolution.

The JWST team measured the composition of the dwarf planets' surfaces, particularly the deuterium (heavy hydrogen, D) to hydrogen (H) ratio in methane.

Deuterium is believed to have formed in the Big Bang, and hydrogen is the most abundant nucleus in the universe.

The D/H ratio on a planetary body yields information about the origin, geologic history and formation pathways of compounds containing hydrogen.

"The moderate D/H ratio we observed with JWST belies the presence of primordial methane on an ancient surface. Primordial methane would have a much higher D/H ratio," Glein said.

"Instead, the D/H ratio points to geochemical origins for methane produced in the deep interior. The D/H ratio is like a window. We can use it in a sense to peer into the subsurface. Our data suggest elevated temperatures in the rocky cores of these worlds so that methane can be cooked up. Molecular nitrogen (N2) could be produced as well, and we see it on Eris. Hot cores could also point to potential sources of liquid water beneath their icy surfaces."

Over the past two decades, scientists have learned that icy worlds can be much more internally evolved than once believed.

Evidence for subsurface oceans has been found at several icy moons such as Saturn's moon Enceladus and Jupiter's moon Europa.

Liquid water is one of the key ingredients in determining potential planetary habitability.

The possibility of water oceans inside Eris and Makemake is something that scientists are going to study in the years ahead.

If either of them is habitable, then it would become the most distant world in the solar system that could possibly support life.

Finding chemical indicators of internally driven processes takes them a step in this direction.

"If Eris and Makemake hosted, or perhaps could still host warm, or even hot, geochemistry in their rocky cores, cryovolcanic processes could then deliver methane to the surfaces of these planets, perhaps in geologically recent times," said Dr. Will Grundy, an astronomer at Lowell Observatory, one of Glein's co-authors and lead author of a companion paper.

"We found a carbon isotope ratio (13C/12C) that suggests relatively recent resurfacing."

This work is part of a paradigm shift in planetary science. It is increasingly being recognized that cold, icy worlds may be warm at heart.

Models developed for this study additionally point to the formation of geothermal gases on Saturn's moon Titan, which also has abundant methane.

Furthermore, the inference of unexpected activity on Eris and Makemake underscores the importance of internal processes in shaping what we see on large KBOs and is consistent with findings at Pluto.

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New 'time travel' study reveals future impact of climate change on coastal marshes

A new Tulane University study published in Nature Communications offers a glimpse into the possible impact of climate change on coastal wetlands 50 years or longer into the future.

Scientists are usually forced to rely on computer models to project the long-term effects of rising seas.

But an unexpected set of circumstances enabled a real-world experiment along the Gulf Coast.

An extensive network of nearly 400 monitoring sites was established along the Louisiana coast after hurricanes Katrina and Rita.

Then the rate of sea-level rise in the region surged to more than 10 millimeters (half an inch) per year -- at least three times the global average.

That exposed the region to the kind of ocean rise not expected until around 2070.

The accelerated rise created a unique opportunity to determine whether the marshes can survive that pace of coastal flooding.

"It is the dream of every field researcher who does experiments -- we can basically travel 50 years into the future to get a peek at what's in store," said Torbjörn Törnqvist, Vokes Geology Professor in the Tulane Department of Earth and Environmental Sciences.

The researchers used new techniques developed by European scientists to measure sea-level rise right off the coast with satellite data, something that was previously not available.

The team then compared the rate of water-level rise at each monitoring site with the rate of wetland elevation change determined by other instruments and found that almost 90% of the sites were in deficit.

"To our knowledge, this is the first time that a climate impact experiment has been carried out over a region this large, based on hundreds of monitoring stations that have collected data for about 15 years," said Guandong Li, a PhD candidate in Earth and Environmental Sciences at Tulane who led the study.

"This has also allowed us to study the climate impact on a heavily human-influenced landscape, rather than a more resilient pristine ecosystem."

Li was investigating the role of land subsidence in coastal Louisiana when a team led by Sönke Dangendorf, the David and Jane Flowerree Professor in Tulane's Department of River-Coastal Science and Engineering, demonstrated the unprecedented rates of sea-level rise along the Gulf and Southeast U.S. coasts since 2010.

"Guandong immediately dropped everything he was working on to take advantage of this unique opportunity," Törnqvist said.

"He set out to answer the key question of whether coastal marshes can keep up with this rate of sea-level rise, as some earlier modeling studies had suggested they can."

If the current climate scenario persists, the rate of sea-level rise by 2070 is expected to be about 7 millimeters (one quarter inch) per year.

The study projects that approximately 75% of wetland sites will be in deficit by that time, potentially resulting in a rate of wetland loss much higher than what has already occurred in the past century.

However, the researchers emphasize that there is hope for a more favorable outcome if immediate action is taken.

By meeting the targets set by the Paris Agreement and reducing carbon emissions, it is possible to shift to a more sustainable climate trajectory that would reduce the rate of wetland loss.

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Reforestation programs could threaten vast area of tropical grasslands

New research led by the University of Liverpool reveals the scale of inappropriate reforestation projects across Africa.

A study published in the journal Science reveals that an area the size of France is under threat by forest restoration initiatives due to inappropriate restoration in the form of tree-planting.

Researchers analysed the areas of land committed to restoration via reforestation and found that many programmes include areas classified as non-forest systems.

They believe that the inclusion of non-forest systems such as savannas and grasslands, which are threatened by increased tree cover, is the key issue.

They warn that planting trees in these grassy areas, which are structurally, functionally and compositionally distinct from forests, could be a risk to wildlife such as rhinos and wildebeest, as well as people who depend on these ecosystems.

Kate Parr, Professor of Tropical Ecology at the University's School of Environmental Sciences and author of the study, said: "Restoration of ecosystems is needed and important, but it must be done in a way that is appropriate to each system.

"Non-forest systems such as savannas are misclassified as forest and therefore considered in need of restoration with trees.

"There is an urgent need to revise definitions so that savannas are not confused with forest because increasing trees is a threat to the integrity and persistence of savannas and grasslands."

"Highlighting this issue now means there is still time to negate this threat and ensure that non-forest systems receive appropriate restoration."

Dr Nicola Stevens, Trapnell Research Fellow in African Environments at the University of Oxford and co-author of the paper said: "The urgency of implementing large-scale tree planting is prompting funding of inadequately assessed projects that will most likely have negligible sequestration benefits and cause potential social and ecological harm."

The study highlights that the issues raised are not unique to Africa and many other non-forest areas, for example the open savannas and grasslands of India and Brazil, could face a similar future due to inappropriate 'restoration' with trees.

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Ancient retroviruses played a key role in the evolution of vertebrate brains

Researchers report February 15 in the journal Cell that ancient viruses may be to thank for myelin -- and, by extension, our large, complex brains. The team found that a retrovirus-derived genetic element or "retrotransposon" is essential for myelin production in mammals, amphibians, and fish. The gene sequence, which they dubbed "RetroMyelin," is likely a result of ancient viral infection, and comparisons of RetroMyelin in mammals, amphibians, and fish suggest that retroviral infection and genome-invasion events occurred separately in each of these groups.

"Retroviruses were required for vertebrate evolution to take off," says senior author and neuroscientist Robin Franklin of Altos Labs-Cambridge Institute of Science.

"If we didn't have retroviruses sticking their sequences into the vertebrate genome, then myelination wouldn't have happened, and without myelination, the whole diversity of vertebrates as we know it would never have happened."

Myelin is a complex, fatty tissue that ensheathes vertebrate nerve axons.

It enables rapid impulse conduction without needing to increase axonal diameter, which means nerves can be packed closer together.

It also provides metabolic support to nerves, which means nerves can be longer.

Myelin first appeared in the tree of life around the same time as jaws, and its importance in vertebrate evolution has long been recognized, but until now, it was unclear what molecular mechanisms triggered its appearance.

The researchers noticed RetroMyelin's role in myelin production when they were examining the gene networks utilized by oligodendrocytes, the cells that produce myelin in the central nervous system.

Specifically, the team was investigating the role of noncoding regions including retrotransposons in these gene networks -- something that hasn't previously been explored in the context of myelin biology.

"Retrotransposons compose about 40% of our genomes, but nothing is known about how they might have helped animals acquire specific characteristics during evolution," says first author Tanay Ghosh, a computational biologist at Altos Labs-Cambridge Institute of Science.

"Our motivation was to know how these molecules are helping evolutionary processes, specifically in the context of myelination."

In rodents, the researchers found that the RNA transcript of RetroMyelin regulates the expression of myelin basic protein, one of the key components of myelin.

When they experimentally inhibited RetroMyelin in oligodendrocytes and oligodendrocyte progenitor cells (the stem cells from which oligodendrocytes are derived), the cells could no longer produce myelin basic protein.

To examine whether RetroMyelin is present in other vertebrate species, the team searched for similar sequences within the genomes of jawed vertebrates, jawless vertebrates, and several invertebrate species.

They identified analogous sequences in all other classes of jawed vertebrates (birds, fish, reptiles, and amphibians) but did not find a similar sequence in jawless vertebrates or invertebrates.

"There's been an evolutionary drive to make impulse conduction of our axons quicker because having quicker impulse conduction means you can catch things or flee from things more rapidly," says Franklin.

Next, the researchers wanted to know whether RetroMyelin was incorporated once into the ancestor of all jawed vertebrates or whether there were separate retroviral invasions in the different branches.

To answer these questions, they constructed a phylogenetic tree from 22 jawed vertebrate species and compared their RetroMyelin sequences.

The analysis revealed that RetroMyelin sequences were more similar within than between species, which suggests that RetroMyelin was acquired multiple times through the process of convergent evolution.

The team also showed that RetroMyelin plays a functional role in myelination in fish and amphibians.

When they experimentally disrupted the RetroMyelin gene sequence in the fertilized eggs of zebrafish and frogs, they found that the developing fish and tadpoles produced significantly less myelin than usual.

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Diverse ancient volcanoes on Mars discovered by planetary scientist may hold clues to pre-plate tectonic activity on Earth

Volcanoes are a common feature on the surfaces of solid planets within the solar system, resulting from magmatic activity occurring within the planetary crust. On Earth, volcanism is driven primarily by heat and crustal recycling associated with plate tectonics, but Mars lacks plate tectonics and the driver of volcanism is not well understood.

Recent research by Professor Joseph MICHALSKI, a geologist in the Department of Earth Sciences at The University of Hong Kong (HKU), has revealed intriguing insights into the volcanic activity on Mars.

He proposes that Mars has significantly more diverse volcanism than previously realised, driven by an early form of crust recycling called vertical tectonics.

The findings, recently published in Nature Astronomy, shed light on the ancient crust of Mars and its potential implications for understanding early crustal recycling on both Mars and Earth.

Traditionally, Mars has been known to have large shield volcanoes similar to those in Hawaii.

However, it was not known that Mars also possessed the diverse, explosive volcanoes that form on Earth due to crustal recycling.

The recent research conducted by Professor Michalski and his international team discover a vast number of diverse volcanoes in the ancient crust of Mars.

'We have known for decades that Mars has volcanoes, but most of the recognised volcanoes correspond to large basaltic shield volcanoes similar to the ones that make up Hawaii,' he explains.

'In this work, we show that the ancient crust has many other types of volcanoes such as lava domes, stratovolcanoes, calderas and large shields of ash, not lava.

Further, most scientists see Mars as a planet composed of basalt, which has low silica content and represents little crustal evolution, but these volcanoes have high silica content which means they formed from a complex process of magma evolution not known before.'

The paper suggests that intense volcanism occurred on ancient Mars, causing the crust to collapse into the mantle, where the rocks re-melted, resulting in magmas that have high silica.

This tectonic process, called vertical tectonics, is hypothesised to have occurred on the ancient Earth, but rocks on Earth from that period (the Archean, more than 3 billion years ago) are highly modified by later geological activity, so we cannot see evidence for this process clearly on this planet.

Therefore, exploring other planets like Mars, which has volcanism but no plate tectonics, can help reveal the mysteries of early crustal recycling on both the Red Planet, and by analogy, on early Earth.

Professor Michalski concluded, 'Mars contains critical geological puzzle pieces that help us understand not only that planet, but the Earth as well.

Martian volcanism is much more complex and diverse than has been previously thought.'

Read more at Science Daily

New study points to more climate extremes

A new study has found similarities between long-term climatic changes in South Australia and temperate agricultural areas in Argentina -- highlighting similarities across these Southern Hemisphere countries.

As temperature records tumble, and the threat of bushfires and dry conditions looms large, an international study by Flinders University and Argentinian researchers renews the urgency of calls to make more concerted efforts to prepare for climate extremes in South Australia.

Highs and lows in temperature and rainfall indices over the past 50 years have shown an increase in maximum and minimum temperatures of 1.1°C and 0.7°C and less precipitation while pointing to more intense and extended drought periods, extreme summer heatwaves alongside occasional extremes such as frost and flood.

South Australia -- often cited as the driest state on the driest continent -- is poised to see more weather extremes in temperature and precipitation with more storm events, longer and more severe droughts and higher temperature peaks up to 3-5°C above current averages likely to follow global trends, the study shows.

"We found remarkable warming signal trends in both hot and cold extreme weather events," says Universidad Nacional del Sur researcher Dr Federico Ferrelli in a new article supported by Argentina's National Scientific and Technical Research Council.

"This reminds us that we need to focus on climate change mitigation and adapt sustainable management plans to better buffer ecosystems and human health and wellbeing, particularly in areas most exposed to these extreme weather patterns."

Flinders University co-author Professor Patrick Hesp, an expert in coastal dune systems, says that if SA's rainfall continue to decline according to such forecasts, "we can expect to see increased soil erosion in dryland agricultural regions and greater mobility of coastal dune systems -- especially on western coast areas where mean annual rainfall is already quite low."

The researchers used 24 climate extreme indices based on Bureau of Meteorology data to find a significant increase in extreme hot events -- including summer days and tropical night temperatures -- as well as daily maximum and daily minimum temperatures.

While cold indices such as frost days show negative trends, heavy and extreme storms have become more severe locally while rain decreases regionally.

Land management practices, including less land clearance, native plant revegetation and more sustainable agricultural practices, is one step in the right direction.

While Argentina and Australia are economically different countries, the researchers emphasise that the imminent impacts of climate change are reflected in both temperate climate zones in the Southern Hemisphere and impacting on a global scale.

For instance, the Pampas Region in Argentina has experienced substantial increases in maximum, minimum and mean temperatures (1.8 °C, 1.2 °C, and 1.2 °C respectively), with some areas affected by falling precipitation and rising aridity.

"Therefore it is imperative to develop sustainable land management policies to address these issues," researchers say.

"Global warming effects ecosystems, biodiversity, agriculture and food security, water resources, and human health and wellbeing.

"It also contributes to economic and social inequities as vulnerable populations and developing countries are often the hardest hit by the effects of climate change."

Including SA's rising 1.8 million population, extreme temperatures could severely impact cardiovascular and respiratory diseases, vector-borne diseases and affect mortality rates, the researchers warn.

Read more at Science Daily

Anthropologists' research unveils early stone plaza in the Andes

Two University of Wyoming anthropology professors have discovered one of the earliest circular plazas in Andean South America, showcasing monumental megalithic architecture, which refers to construction that uses large stones placed upright with no mortar.

Located at the Callacpuma archaeological site in the Cajamarca Basin of northern Peru, the plaza is built with large, vertically placed megalithic stones -- a construction method previously unseen in the Andes.

Associate Professor Jason Toohey, project lead, and Professor Melissa Murphy have been researching this topic since the project's inception in 2015.

Excavations took place in the plaza starting in 2018.

Their paper, which reports new data on this earliest known megalithic circular plaza in the northern Andes, is titled "A Monumental Stone Plaza at 4750 BP in the Cajamarca Valley of Peru" and has been published today (Feb.

14) in the peer-reviewed journal Science Advances.

Radiocarbon dating places its initial construction around 4,750 years ago during the Late Preceramic Period, making it one of the earliest instances of such architecture in the Americas.

To better understand this timeline, the team carefully excavated within the plaza, uncovering artifacts related to life in the past and collecting charcoal samples for dating.

All material remains then were cleaned, processed and analyzed in the laboratory.

"This structure was built approximately 100 years before the Great Pyramids of Egypt and around the same time as Stonehenge," Toohey says.

These dates signify that the circular plaza at Callacpuma is the earliest known example of monumental and megalithic architecture in the Cajamarca Valley -- and one of the earliest examples in ancient Peru.

"It was probably a gathering place and ceremonial location for some of the earliest people living in this part of the Cajamarca Valley," Toohey adds.

"These people were living a primarily hunting-and-gathering lifestyle and probably had only recently begun growing crops and domesticating animals."

The plaza is formed by two concentric walls and measures about 60 feet in diameter.

The project is led by Toohey and Patricia Chirinos Ogata from the University of California-Santa Barbara.

The team also includes Murphy, as well as undergraduate and graduate students from Peru and the U.S.

Toohey is an anthropological archaeologist who is dedicated to taking a holistic and multidisciplinary approach to the field.

He has conducted fieldwork in the Peruvian Andes since 2003.

The department head for anthropology at UW, Murphy is a biological anthropologist specializing in bioarchaeology and committed to multidisciplinary approaches within anthropology.

Read more at Science Daily