воскресенье, 26 января 2020 г.

2020 January 26 Hills, Ridges, and Tracks on Mars Image Credit:...

2020 January 26

Hills, Ridges, and Tracks on Mars
Image Credit: NASA, JPL-Caltech, MSSS; Processing & Copyright: Thomas Appere

Explanation: Sometimes, even rovers on Mars stop to admire the scenery. Just late last November the Curiosity rover on Mars paused to photograph its impressive surroundings. One thing to admire, straight ahead, was Central Butte, an unusual flat hill studied by Curiosity just a few days before this image was taken. To its right was distant Mount Sharp, the five-kilometer central peak of entire Gale crater, the interior of which Curiosity is exploring. Mount Sharp, covered in sulfates, appears quite bright in this colorized, red-filtered image. To the far left, shrouded in a very dark shadow, was the south slope of Vera Rubin ridge, an elevation explored previously by Curiosity. Between the ridge and butte were tracks left by Curiosity’s wheels as they rolled forward, out of the scene. In the image foreground is, of course, humanity’s current eyes on Mars: the complex robotic rover Curiosity itself. Later this year, if all goes well, NASA will have another rover – and more eyes – on Mars. Today you can help determine the name of this rover yourself, but tomorrow is the last day to cast your vote.

∞ Source: apod.nasa.gov/apod/ap200126.html

* This article was originally published here

How social structures emerge: Computer simulations uncover universality in cultural anthropology observations

What rules shaped humanity's original social networks? Researchers in Japan developed new mathematical models to understand what conditions produced traditional community structures and conventions around the world, including taboos about incest.

How social structures emerge: Computer simulations uncover universality in cultural anthropology observations
Illustration of communities joining through a marriage [Credit: © Caitlin Devor,
University of Tokyo, CC BY 4.0]
"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.

Researchers used statistical physics and computer models common in evolutionary biology to explain the origin of common community structures documented by cultural anthropologists around the world.

The earliest social networks were tightly knit cultural groups made of multiple biologically related families. That single group would then develop relationships with other cultural groups in their local area.

In the 1960s, cultural anthropologists documented social networks of indigenous communities and identified two kinship structures common around the world. In areas with hunter-gatherer communities, anthropologists documented direct-exchange kinship structures where women from two communities change places when they marry. In areas with agrarian farming communities, kinship structures of generalized exchange developed where women move between multiple communities to marry.

"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, whose interdisciplinary interests in physics, math and anthropology motivated this research study.

Experts in anthropology consider the incest taboo to be an extremely common social rule affecting kinship structures. The ancient incest taboo focused on social closeness, rather than genetic or blood relationships, meaning it was taboo to marry anyone born into the same cultural group.

How social structures emerge: Computer simulations uncover universality in cultural anthropology observations
Graphical representations of simulated social networks. Researchers used computer simulations based on principles
of statistical physics and evolutionary biology to model how human societies would form under different conditions.
Direct-exchange (left), generalized-exchange (center), and restricted-exchange (right) social structure
models observed by cultural anthropologists in the 1960s are represented graphically
[Credit: Kenji Itao, University of Tokyo, CC BY-SA 4.0]
Itao and Kaneko designed a mathematical model and computer simulation to test what external factors might cause generations of biologically related families to organize into communities with incest taboos and direct or generalized exchange of brides.

"Traditionally, it is more common for women to move to a new community when they marry, but we did not include any gender differences in this computer simulation," explained Itao.

Simulated family groups with shared traits and desires naturally grouped together into distinct cultural groups. However, the traits the group possessed were different from the traits they desired in marriage partners, meaning they did not desire spouses similar to themselves. This is the underlying cause of the traditional community-based incest taboo suggested by the study.

When the computer simulation pushed communities to cooperate, generalized exchange kinship structures arose. The simulation demonstrated different kinship structures, including the direct exchange basic structure, emerge depending on the strength of conflict to find brides and the necessity of cooperation with specific other communities.

"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.

The current computer model is simple and only included factors of conflict and cooperation affecting marriage, but researchers hope to continue developing the model to also consider economic factors that might cause communities to separate into different classes. With these additions, the theory can hopefully be extended to explore different communities in the modern, global society.

"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," said Itao.

The study is published in the Proceedings of the National Academy of Sciences.

Source: University of Tokyo [January 21, 2020]

* This article was originally published here

Lordenshaw Bronze Age Rock Art (Main Panel), Lordenshaw Hill, Northumberland, 25.1.20.This is my...

Lordenshaw Bronze Age Rock Art (Main Panel), Lordenshaw Hill, Northumberland, 25.1.20.

This is my first visit to this site. As I walked up to it; a passing hiker told me I would be disappointed. I think he missed the point; it’s the variety, sophistication and sheer volume of the symbols here that are special.

* This article was originally published here

A few papers

It's been a slow and somewhat disappointing start to the year, but this week saw the publication of a few interesting papers: Ancient West African foragers in the context of African population history Early Pastoral Economies and Herding Transitions in Eastern Eurasia Genetic insights into the social organisation of the Avar period elite in the 7th century AD Carpathian Basin Genome‐wide SNP

* This article was originally published here

Buttony 4 Prehistoric Rock Art, Wooler, Northumberland, 25.1.20.Just occasionally that wet and...

Buttony 4 Prehistoric Rock Art, Wooler, Northumberland, 25.1.20.

Just occasionally that wet and difficult walk in the dark woodland is worth it…

* This article was originally published here

Life's Frankenstein beginnings

When the Earth was born, it was a mess. Meteors and lightning storms likely bombarded the planet's surface where nothing except lifeless chemicals could survive. How life formed in this chemical mayhem is a mystery billions of years old. Now, a new study offers evidence that the first building blocks may have matched their environment, starting out messier than previously thought.

Life's Frankenstein beginnings
Szostak believes the earliest cells developed on land in ponds or pools, potentially in volcanically active regions.
Ultraviolet light, lightning strikes, and volcanic eruptions all could have helped spark the chemical
reactions necessary for life formation [Credit: Don Kawahigashi/Unsplash]
Life is built with three major components: RNA and DNA--the genetic code that, like construction managers, program how to run and reproduce cells--and proteins, the workers that carry out their instructions. Most likely, the first cells had all three pieces. Over time, they grew and replicated, competing in Darwin's game to create the diversity of life today: bacteria, fungi, wolves, whales and humans.

But first, RNA, DNA or proteins had to form without their partners. One common theory, known as the "RNA World" hypothesis, proposes that because RNA, unlike DNA, can self-replicate, that molecule may have come first. While recent studies discovered how the molecule's nucleotides--the A, C, G and U that form its backbone--could have formed from chemicals available on early Earth, some scientists believe the process may not have been such a straightforward path.

"Years ago, the naive idea that pools of pure concentrated ribonucleotides might be present on the primitive Earth was mocked by Leslie Orgel as 'the Molecular Biologist's Dream,'" said Jack Szostak, a Nobel Prize Laureate, professor of chemistry and chemical biology and genetics at Harvard University, and an investigator at the Howard Hughes Medical Institute. "But how relatively modern homogeneous RNA could emerge from a heterogeneous mixture of different starting materials was unknown."

In a paper published in the Journal of the American Chemical Society, Szostak and colleagues present a new model for how RNA could have emerged. Instead of a clean path, he and his team propose a Frankenstein-like beginning, with RNA growing out of a mixture of nucleotides with similar chemical structures: arabino- deoxy- and ribonucleotides (ANA, DNA, and RNA).

In the Earth's chemical melting pot, it's unlikely that a perfect version of RNA formed automatically. It's far more likely that many versions of nucleotides merged to form patchwork molecules with bits of both modern RNA and DNA, as well as largely defunct genetic molecules, such as ANA. These chimeras, like the monstrous hybrid lion, eagle and serpent creatures of Greek mythology, may have been the first steps toward today's RNA and DNA.

"Modern biology relies on relatively homogeneous building blocks to encode genetic information," said Seohyun Kim, a postdoctoral researcher in chemistry and first author on the paper. So, if Szostak and Kim are right and Frankenstein molecules came first, why did they evolve to homogeneous RNA?

Kim put them to the test: He pitted potential primordial hybrids against modern RNA, manually copying the chimeras to imitate the process of RNA replication. Pure RNA, he found, is just better--more efficient, more precise, and faster--than its heterogeneous counterparts. In another surprising discovery, Kim found that the chimeric oligonucleotides--like ANA and DNA--could have helped RNA evolve the ability to copy itself. "Intriguingly," he said, "some of these variant ribonucleotides have been shown to be compatible with or even beneficial for the copying of RNA templates."

If the more efficient early version of RNA reproduced faster than its hybrid counterparts then, over time, it would out-populate its competitors. That's what the Szostak team theorizes happened in the primordial soup: Hybrids grew into modern RNA and DNA, which then outpaced their ancestors and, eventually, took over.

"No primordial pool of pure building blocks was needed," Szostak said. "The intrinsic chemistry of RNA copying chemistry would result, over time, in the synthesis of increasingly homogeneous bits of RNA. The reason for this, as Seohyun has so clearly shown, is that when different kinds of nucleotides compete for the copying of a template strand, it is the RNA nucleotides that always win, and it is RNA that gets synthesized, not any of the related kinds of nucleic acids."

So far, the team has tested only a fraction of the possible variant nucleotides available on early Earth. So, like those first bits of messy RNA, their work has only just begun.

Source: Harvard University [January 22, 2020]

* This article was originally published here


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