Tag Archives: structure

Of brides and men: how the search for a spouse creates social structures

New research from the University of Tokyo (UoT) is looking into how human social networks form and found that they naturally arise from simple, direct-exchange marriage relationships between familiar groups.

Image via Pixabay.

The team developed new mathematical models to study how traditional community structures and conventions arose around the world, including wide-spread taboos such as incest. For their study, they also drew on statistical physics models employed by evolutionary biologists and data on community structures documented by anthropologists around the world.

The original social network

“We think this is the first time cultural anthropology and computer simulations have met in a single research study,” said Professor Kunihiko Kaneko, an expert in theoretical biology and physics from the University of Tokyo Research Center for Complex Systems Biology.

“Anthropologists have documented kinship structures all over the world, but it still remains unclear how those structures emerged and why they have common properties,” said Kenji Itao, a first year master’s degree student in Kaneko’s laboratory, and first author of the study.

The team wanted to find the underlying mechanisms that shape human social networks, and how they lead to the traditional community structures and conventions we see around the world.

Back in the 1960s, cultural anthropologists studied the social networks among indigenous communities around the world, identifying two structures that seemed to naturally arise wherever they went. Among hunter-gatherers, direct-exchange kinship structures were common. These involve women from two different communities changing places when they marry (i.e. an “exchange of brides among more than two clans”). Agrarian societies, meanwhile, develop kinship structures where women move between multiple communities to marry.

“In human society, a family and kinship are formed by marriage and descent. In indigenous societies, families sharing a common ancestor are called a lineage. Lineages form a socially related group, called a clan, in which common culture is shared,” the authors write.

“Social relationships with others, such as cooperation, rivalry, or marriage, are mostly determined by the clans the parties belong to”.

The first social networks were tightly-knit structures formed among (biologically-related) families, the team explains. Such groups would then develop various relationships with other cultural groups in their local area as they interacted.

Itao and Kaneko used computer modeling and simulation to gauge which external factors could drive biologically-related families to organize into larger communities and control the exchange of brides in between lineages (i.e. the development of the incest taboo). They explain that incest is almost universally considered a taboo in human societies; however, the ancient focus of the taboo was on social closeness rather than blood ties — marrying someone born into the same cultural group as you, not necessarily someone you’re related to, was seen as taboo.

While “it is more common for women to move to a new community when they marry”, Itao explains, the model they used for this study didn’t make any distinction based on gender in this regard.

Someone not like me, please

They report that simulated families which shared traits or interests naturally coalesced into distinct cultural groups. However, the traits individual members possessed were different from the ones they desired in a spouse — the simulated actors desired to marry someone who wasn’t similar to themselves. This, they believe, is the underlying cause of community-based incest taboos.

When the model pushed these communities to cooperate, they formed generalized kinship exchange structures. Exactly which shape these structures took mainly depended on how difficult it was to find suitable brides and how much cooperation or conflict with other communities was necessary in order to secure these women.

The findings are based on a simple model that only included how social conflict and cooperation relate to marriage; the team hopes to further expand on it and include economic factors (which they say can cause communities to separate into classes). A better model could be used to expand the research to different communities in the modern world.

“It is rewarding to see that the combination of statistical physics and evolution theory, together with computer simulations, will be relevant to identify universal properties that affect human societies,” said Kaneko.

“I would be glad if perhaps our results can give field anthropologists a hint about universal structures that might explain what they observe in new studies,” Itao adds.

The paper “Evolution of kinship structures driven by marriage tie and competition” has been published in the journal Proceedings of the National Academy of Sciences.

Fox spine.

Bones have a fractal-like structure making them super strong and flexible

Zoom in close enough and bones betray an incredible structural sophistication.

Fox spine.

Fragment of fox spine.
Image via Pixabay.

Researchers from the University of York and the Imperial College London have produced a 3D, nanoscale reconstruction of bone’s mineral structure. Their work reveals a surprising ‘hierarchical organisation’ which underpins the material’s mechanical versatility.

Bred in the bones

Bone is a surprisingly versatile material. Different varieties of bone can be both strong and flexible, maintaining the lithe form of cheetas, the impressive bulk of elephants, or the lightweight frames of birds alike.

These enviable properties are owed to a sophisticated internal structure. However, the exact nature of this structure and of the interactions between the main components of bone — collagen protein strands and the mineral hydroxyapatite — has so far been unknown. According to new research, however, the ‘hierarchical organization’ of bone is based on small elements coming together to form larger and larger structures.

Their results have shown that individual mineral crystals inside bone tissue come together into larger, more complex structures — ones that come together into even more complex levels of organization, the team reports.

For the findings, the team used advanced 3D nanoscale imaging of the mineral component of human bone. They used a combination of electron microscopy-based techniques to reveal its main mineral building blocks. These nanometer-sized crystals of apatite take on a curved, needle-like shape and merge together into larger, twisted platelets that resemble the shape of propeller blades.

These blades, in turn, merge together and split apart throughout the protein phase of the bone. This overarching weaving pattern of mineral and protein is what provides the material’s strength and flexibility.

“Bone is an intriguing composite of essentially two materials, the flexible protein collagen and the hard mineral called apatite,” Lead author, Associate Professor Roland Kröger, says Associate Professor the University of York’s Department of Physics, lead author of the paper.

“The combination of the two materials in a hierarchical manner provides bone with mechanical properties that are superior to those of its individual components alone and we find that there are 12 levels of hierarchy in bone.”

The paper describes the structure as “fractal-like”, containing 12 different levels of complexity. The needle-like crystals merge into the propeller-like platelets in a roughly parallel arrangement with gaps of roughly 2 nanometers between them. These stacks of platelets, along with some single platelets and acicular crystals, come together into larger “polycrystalline aggregates”. These latter ones are larger laterally than the collagen fibers, and can even span several adjacent fibers — providing a continuous, cross-fiber mineral structure that lends resilience to the bone.

Bone structure.

The model of crystal organization in bone proposed by the team.
Patterns specified by the model at the top alongside the mineral organization in different directions (bottom).
Image credits N. Reznikov et al., 2018, Science.

These nanostructures woven into the bone also show a slight curvature, twisting the overall geometry, the team further reports. For example, the individual crystals are curved, the protein (collagen) strands are braided together, mineralized collagen fibrils twist, and the bone themselves have a twist (such as a curvature of a rib).

The team concludes that this fractal-like structure they discovered embedded in our bones is one of the cornerstones of their remarkable physical properties.

The paper “Fractal-like hierarchical organization of bone begins at the nanoscale” has been published in the journal Science.

Viral shell.

Boiling-acid-proof virus’ outer shell structure could inspire better medication, sturdier buildings

The shell of a virus which calls boiling acid pools of Yellowstone home could show us the way to more powerful drugs, stronger materials, and more resilient buildings.

Viral shell.

The virus’ unusual envelope structure, never before seen in nature.
Image credits Peter Kasson et al., 2017.

First isolated in 2002 by Pasteur Institute researchers, the virus known as Acidianus hospitalis Filamentous Virus 1 is scaringly hard to kill. This bug lives in the hot-springs of Yellowstone National Park, pools of acid bubbling to temperatures as high as 237 degrees Celsius (455-ish degrees Fahrenheit), which can dissolve people.

Naturally, anything that can live in such conditions is bound to have some pretty impressive tricks up their sleeves — or up their viral casing, as an international team of researchers reports. The finding could open up new avenues of research into material sciences, with applications from pinpoint drug delivery mechanisms to earthquake-resistant buildings.

“Anytime you find something that behaves really differently, especially something this stable, it’s interesting and potentially useful,” says first author Peter M. Kasson, MD, PhD, from the University of Virginia School of Medicine Department of Molecular Physiology and Biological Physics

“When you’re doing curiosity-driven science that finds something new, in the back of your mind, you think, ‘Hey, this is really different. What might it be good for?’ And this has many potential applications.”

Thick-skinned

The secret behind the virus’ extreme resilience lies in its membrane, the team reports. Although it’s outer shell is only half as thick as known cell membranes, it’s ridiculously stable. The molecules which make up the membrane are stacked up in a horseshoe-shaped arrangement, creating a very dense and durable structure.

The team had to rely on the UVA’s Titan Krios electron microscope to probe the virus’ secrets. This device is so sensitive, that it had to be installed underground to insulate it from vibrations — the slightest of which would be enough to throw off its calibrations. Armed with these readings, the team turned to computer modeling to tease out the structure of the membrane’s lipid molecules.

“Essentially, we encode everything we know about the physics of these molecules and then come up with models that are both consistent with the basic physics and consistent with the observations from the electron microscope,” Kasson explains.

Duplicating this structure might help scientists paste the virus’ defenses into other materials. These could have a dramatic impact in construction, material science, every field where a super-resilient material could come in handy.

Nanomedicine stands to benefit a whole lot if we manage to reverse-engineer the virus’ shell. We could use the structures to create microscopic particles to protect drugs from our body’s effort to metabolize them, allowing for pinpoint delivery of more efficient drug doses. For example, injecting drugs directly into tumors.

 

“It’s amazing how much we still don’t know about life as it exists on Earth — at the bottom of the ocean, in the deep sea vents, or places like Yellowstone or Iceland where you have these very strange environments we think of as inhospitable to life,” paper co-author Edward Egelman said.

“But the things that live there, they may look at our environment and think, ‘Strange.'”

The paper “Model for a novel membrane envelope in a filamentous hyperthermophilic virus” has been published in the journal eLife.

The eye of the Sahara

A topographic reconstruction (scaled 6:1 on the vertical axis) from satellite photos. False coloring as follows: bedrock=brown, sand=yellow/white, vegetation=green, salty sediments=blue. Credit: NASA

This has got to be one of the strangest places on Earth- – but you couldn’t make much of it if you were just walking by.

It’s located in a rather remote area and the few people who noticed something odd about it didn’t know just how odd it really was. That’s why the 50 km formation didn’t receive much attention until some astronauts made reports about it .

Photo by NASA.

Located in Mauritania, the Eye of the Sahara is not really what you would call a structure, but rather a huge circular formation; it was originally thought to be a crater, but the more recent and accepted theories suggest that it is, in fact, a product of erosion that took place in geological time.

Also known as the Richat Structure, the Eye of the Sahara has been studied by numerous geologists.

“The Richat structure (Sahara, Mauritania) appears as a large dome at least 40 km in diameter within a Late Proterozoic to Ordovician sequence. Erosion has created circular cuestas represented by three nested rings dipping outward from the structure. The center of the structure consists of a limestone-dolomite shelf that encloses a kilometer-scale siliceous breccia and is intruded by basaltic ring dikes, kimberlitic intrusions, and alkaline volcanic rocks” – small excerpt from a paper.

You can also see it on Google Maps, it’s really a brilliant view, and you can zoom in and out for proportions (coordinates are 21.124217, -11.395569).

 

Picture sources: 1 2 3

The Thickest Layer of the Earth

The Earth can be divided into four main layers: the solid crust on the outside, the mantle, the outer core and the inner core. Out of them, the mantle is the thickest layer, while the crust is the thinnest layer.

The Earth’s structure

Artistic depiction of the Earth's structure. Image via Victoria Museum.

Artistic depiction of the Earth’s structure. Image via Victoria Museum.

The Earth’s structure can be defined in several ways, but general, we see the Earth as having a solid crust on the outside, an inner and an outer core, and the mantle in between. The crust’s thickness varies between some 10 km and just over 70 km, having an average of about 40 km. The core has, in total, a radius of 3500 km, but it is generally viewed as two distinct parts:

  • the solid inner core, with a radius of 1220 km
  • the viscous outer core, with a radius of 2300 km

The mantle’s thickness is about 2900 km – so if you consider the Earth’s core as one big thing, then the core is the “thickest layer” (though has a bigger radius is probably a better way of saying it) – but the idea of a separate outer and inner core is generally accepted.

The Mantle – thickness and composition

The mantle comprises about 83% of the Earth’s volume. It is divided into several layers, based on different seismological characteristics (as a matter of fact, much of what we know about the mantle comes from seismological information – more on that later in the article). The upper mantle extends from where the crust ends to about 670 km. Even though this area is regarded as viscous, you can also consider it as formed from rock – a rock called peridotite to be more precise. A peridotite is a dense, coarse-grained igneous rock, consisting mostly of olivine and pyroxene, two minerals only found in igneous rocks.

Peridotite, as seen on the Earth’s surface. Image via Pittsburgh University.

But it gets even more complicated. The crust is divided into tectonics plates, and those tectonic plates are actually thicker than the crust itself, encompassing the top part of the mantle. The crust and that top part of the mantle (going 00 to 200 kilometers below surface, is called the asthenosphere. Scientific studies suggest that this layer has physical properties that are different from the rest of the upper mantle. Namely, the rocks in this part of the mantle are more rigid and brittle because of cooler temperatures and lower pressures.

Below that, there is the lower mantle – ranging from 670 to 2900 kilometers below the Earth’s surface. This is the area with the highest temperatures and biggest pressures, reaching all the way to the outer core.

Mantle Trivia: Even though you can consider the mantle as molten rock or magma, modern research found that the mantle has between 1 and 3 times more water than all the oceans on Earth combined.

How can we study the mantle?

Waves propagating from Earthquakes through the Earth. Image via Brisith Geological Survey.

Waves propagating from Earthquakes through the Earth. Image via Brisith Geological Survey.

Pretty much all the practical geology we do takes places at the crust. All the rock analysis, the drilling… everything we do is done in the crust. The deepest drill ever is some 12 km below the surface… so then how can we know the mantle?

As I said earlier, most of what we know about the mantle comes from seismological studies. When big earthquakes take place, the waves propagate throughout the Earth, carrying with them information from the layers they pass through – including the mantle. Furthermore, modern simulations in the lab showed how minerals likely behave at those temperatures and pressures, and we also have indirect gravitational and magnetic information, as well as studies on magma and crystals found on the surface. But the bulk of the information comes from seismic analysis.

Image via Wiki Commons.

Seismic waves, just like light waves, reflect, refract and diffract when they meet a boundary – that’s how we know where the crust ends and where the mantle begins, and the same goes for the mantle and the core. The waves also behave differently depending on different properties, such as density and temperature.

In the mantle, temperatures range between 500 to 900 °C (932 to 1,652 °F) at the upper boundary with the crust; to over 4,000 °C (7,230 °F) at the boundary with the core. Thanks to the huge temperatures and pressures within the mantle, the rocks within undergo slow, viscous like transformations  there is a convective material circulation in the mantle. How material flows towards the surface (because it is hotter, and therefore less dense) while cooler material goes down. Many believe that this convection actually is the main driver behind plate tectonics.

Mantle convection may be the main driver behind plate tectonics. Image via University of Sydney.

Another interesting fact about the mantle: Earthquakes at the surface are a result of stick-slip faulting; rocks in the mantle can’t fault though, yet they sometimes generate similar earthquakes. It’s not clear why this happens, but several mechanisms have been proposed, including dehydration, thermal runaway, and mineral phase change. This is just a reminder of how little we still know about our planet: we’ve only scratched the surface of the thinnest layer, the crust.

Previously unseen huge structure located within our galaxy

Researchers have confirmed the presence of a previously undiscovered structure located in the center of the Milky Way, a discovery likened with the discovery of a new continent on Earth, in terms of scale. Doug Finkbeiner, an astronomer at Harvard-Smithsonian Centre for Astrophysics (CfA) in Cambridge, Massachusetts, who discovered the structure using NASA’s Fermi Gamma-ray Space Telescope believes it is probably a remnant of an eruption from a massive blackhole in the center of our galaxy.

“What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic centre. We don’t fully understand their nature or origin,” he was quoted as saying by a joint CfA and NASA release.

Credits: NASA

The structure is definitely millions of years old, but how many millions, is really anybody’s guess; also, several million years don’t mean that much at a galactic scale. The discovery hasn’t been published yet, but a paper will soon appear in the upcoming edition of the The Astrophysical Journal.

The gamma ray detector they will be using to analyze the data is the most sophisticated, accurate and sensitive one up to date, Fermi’s Large Area Telescope(LAT). A number of people have analyzed it, and so far, everything seems to back up this astonishing discovery.

“The LAT team confirmed the existence of an extended structure in the direction of the inner part of the Milky Way and we’re in the process of performing a deeper analysis to better understand it,” said Simona Murgia, a Fermi researcher at the SLAC National Accelerator Laboratory in California.

3D structure of humans finally decoded

dna_500

It’s quite obvious that genetics is the most important step in our evolution that we have to take and although the molecular structure of DNA has been discovered more than half a century ago, its three dimensional structure remained a mystery. However, recently a team led by researchers from Harvard University, the Broad Institute of Harvard and MIT and the University of Massachusetts Medical School managed to solve this puzzle, paving the way for new insights into genomic functions and greatly expanding our understanding limits.

In order to accomplish this task, they employed a novel technology they call Hi-C and found out how DNA folds; the goal was to find out how our cells can somehow store three billion base pairs of DNA without having any of its functions blocked or impaired.

“We’ve long known that on a small scale, DNA is a double helix,” says co-first author Erez Lieberman-Aiden, a graduate student in the Harvard-MIT Division of Health Science and Technology and a researcher at Harvard’s School of Engineering and Applied Sciences and in the laboratory of Eric Lander at the Broad Institute. “But if the double helix didn’t fold further, the genome in each cell would be two meters long. Scientists have not really understood how the double helix folds to fit into the nucleus of a human cell, which is only about a hundredth of a millimeter in diameter. This new approach enabled us to probe exactly that question.”

It has to be said, this Hi-C technology is almost as amazing as the discovery itself, at least from where I’m standing. To be able to go to such a level that allows assessment of the three dimensional interactions between DNA is just amazing. Regarding the importance of ‘decoding’ the structure, it basically means scientists will be able to find out how to turn most genes on and off:

“Cells cleverly separate the most active genes into their own special neighborhood, to make it easier for proteins and other regulators to reach them,” says Job Dekker, associate professor of biochemistry and molecular pharmacology at UMass Medical School and a senior author of the Science paper.

At an even finer scale, scientists had to reach out for mathematics, because DNA takes a shape of what is called in mathematics a ‘fractal‘. The specific architecture they found was named a ‘fractal globule’ that allows the cell to pack DNA unbelievable tightly. Just so you can make an idea, the density of information stored there is trillions and trillions of times bigger than that of the world’s best computer chip.

fractal-dna

“Nature’s devised a stunningly elegant solution to storing information — a super-dense, knot-free structure,” says senior author Eric Lander, director of the Broad Institute, who is also professor of biology at MIT, and professor of systems biology at Harvard Medical School.

The idea of such a structure has in fac been suggested a while back, but it was as good as any guess at the moment, with no proof to back it up. However, thanks to this new kind of technology, the amazing truth was observed and scientists were able to solve the puzzle.

“By breaking the genome into millions of pieces, we created a spatial map showing how close different parts are to one another,” says co-first author Nynke van Berkum, a postdoctoral researcher at UMass Medical School in Dekker’s laboratory. “We made a fantastic three-dimensional jigsaw puzzle and then, with a computer, solved the puzzle.”