среда, 9 октября 2019 г.

Moulds for Late Iron Age and Medieval Scottish Penannular Brooches, Kilmartin Museum,...





Moulds for Late Iron Age and Medieval Scottish Penannular Brooches, Kilmartin Museum, Argyll, 28.9.19.


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Upper Largie Prehistoric Cist Grave (2000 to 1500BCE), Kilmartin Museum, Kilmartin Glen,...




Upper Largie Prehistoric Cist Grave (2000 to 1500BCE), Kilmartin Museum, Kilmartin Glen, Argyll, 28.9.19.


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Model of Prehistoric Glebe Cairn, Kilmartin Museum, Kilmartin Glen, Argyll, 28.9.19.A...


Model of Prehistoric Glebe Cairn, Kilmartin Museum, Kilmartin Glen, Argyll, 28.9.19.


A scale model from the account given during its 19th century excavation.


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Bright Eyes When light floods into our eyes, cells in the…


Bright Eyes


When light floods into our eyes, cells in the retina called photoreceptors turn colourful chemical signals into electrical ones – these pass down through layers of different cells towards the optic nerve bound for the brain. These first steps of vision take a fraction of a second, but are fragile – exposure to too much light, or some medications, can damage eye cells and make them difficult to study. This retinal organoid grows from pluripotent stem cells nurtured in a lab over an artificial ‘tissue’ that provides nurturing chemicals, just as the bloodstream would feed the developing eye. Some of its cells (artificially stained blue) transform into different photoreceptors known as rods (red) and cones (green). This retina-on-a-chip can now be used to test drugs to improve eye health, or identify those with potentially harmful side-effects.


Written by John Ankers



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Two Ancient Migration Events in the Andromeda Galaxy



The globular clusters studied (lower right insets), indicated by colored circles, are located in the outer halo of the Andromeda Galaxy, beyond the bright disk of the galaxy (upper left inset). The star clusters separate into two groups — those associated and unassociated with stellar streams — that have very different orbits, a result that points to two discrete migration events in the history of the galaxy. The color of each circle indicates the line-of-sight velocity of the corresponding star cluster.Credit: Australian National University / NSF’s National Optical-Infrared Astronomy Research Laboratory. DownloadJPG1.8MB |TIFF3MB





Gemini Observatory with NSF’s National Optical-Infrared Astronomy Research Laboratory


Astronomers have uncovered two historic events in which the Andromeda Galaxy underwent major changes to its structure. The findings shed light not only on the evolution and formation of the Andromeda Galaxy, but to our own Milky Way Galaxy as well. Two of the facilities in NSF’s National Optical-Infrared Astronomy Research Laboratory, Kitt Peak National Observatory and the International Gemini Observatory, played critical roles in the research, now published in the latest issue of the journal Nature.


Large galaxies like the one we live in, the Milky Way, are believed to grow through repeated merging with smaller, dwarf galaxies. Gas and dwarf galaxies in the vast cosmic web follow the gravitational paths laid out by dark matter — traversing filaments, they migrate slowly toward collections of dark matter and assemble into large galaxies. As dwarf galaxies are pulled in by gravity, they are also pulled apart, leaving behind long trailing streams of stars and compact star clusters.


Astronomers have uncovered evidence for two major migration events in the history of our large galactic neighbor, the Andromeda Galaxy (also known as M31). The more recent migration event occurred a few billion years ago and the older event many billions of years before that. The evidence for the two events comes from “galactic archaeology,” the use of the motions and properties of stars and stellar clusters to reconstruct the formation and evolutionary history of galaxies.


In the case of the Andromeda Galaxy, the team of galactic archaeologists, led by Dr. Dougal Mackey (Australian National University) and Professor Geraint Lewis (University of Sydney), measured the velocities of 77 of the Andromeda Galaxy’s compact star clusters, using the 4-meter Mayall telescope at Kitt Peak National Observatory, the 8-meter Gemini North telescope on Maunakea, Hawai‘i, and other facilities. The star clusters are all located in the outer halo of the galaxy. The outer regions of the galaxy are of particular interest because the dynamical signature of migration events persists longer there.


“By tracing the faint remains of dwarf galaxies with star clusters, we’ve been able to recreate the way the Andromeda Galaxy drew them in at different times, from what’s known as the ‘cosmic web’ of matter that threads the Universe,” Lewis said.


The team found that the star clusters divide into two populations, a young group associated with stellar streams, and an older group that has no such association. The two populations both orbit the Andromeda Galaxy, but their orbital axes are nearly perpendicular to each other.


The different orbits are evidence for two distinct accumulation events. The stellar streams associated with the more recent event are still present, but streams from the older event are long gone.


According to Mackey, reconstructing the formation history of the Andromeda Galaxy provides insights into the history of our own galaxy, the Milky Way.


“One of our main motivations in studying astronomy is to understand our place in the Universe. A way of learning about the Milky Way is to study galaxies that are similar to it, and try to understand how these systems formed and evolved.” Studying the Andromeda Galaxy, “can actually be easier than looking at the Milky Way. Because we live inside it, that can make certain types of observations quite difficult,” Mackey said.


Astronomer Knut Olsen of NSF’s National Optical-Infrared Astronomy Research Laboratory, who studies the formation of galaxies but was not part of the study said, “This work shows that galaxies as massive as the Large Magellanic Cloud have merged with the Andromeda Galaxy at least twice in its history.” The Large Magellanic Cloud is a companion galaxy to the Milky Way that is easily visible to the naked eye in the Southern hemisphere. Olsen added, “If we could have observed these events taking place billions of years ago, we would have been treated to a real display of cosmic fireworks as new stars formed!”


“This is a great example of NSF-sponsored facilities being used in unison to unravel the mysteries of our neighbor galaxy M31, something that NSF’s National Optical-infrared Astronomy Research Laboratory should make much easier,” noted Ralph Gaume, Division Director for NSF’s Division of Astronomical Sciences.







More Information


The study, published in Nature, analyzed data from the Pan-Andromeda Archaeological Survey (PAndAS):“Two major accretion epochs in M31 from two distinct populations of globular clusters,” Mackey et al. 2019, Nature.


NSF’s National Optical-Infrared Astronomy Research Laboratory, the US center for ground-based optical-infrared astronomy, operates the Gemini Observatory, Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and the Large Synoptic Survey Telescope (LSST). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai’i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local Communities in Chile, respectively.



Science Contacts:

Dr. Dougal Mackey
Research School of Astronomy and Astrophysics
Australian National University, College of Science
Email: dougal.mackey@anu.edu.au
Desk: +61 2 6125 0214
Cell: +61 457 871 313


Professor Geraint Lewis
Sydney Institute for Astronomy
School of Physics, University of Sydney
Email: geraint.lewis@sydney.edu.au
Cell: +61 424 254 551


Dr. Joan Najita
NSF’s National Optical-Infrared Astronomy Research Laboratory
950 N. Cherry Ave. Tucson, AZ 85719 USA
Email: najita@noao.edu
Desk: +1 520-318-8416



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Astronomers show how supergiant stars repeatedly cool and heat up




The star HR 5271A is one of the four hyper-giants investigated. 


(c) A. Lobel/NASA/Spitzer Space Telescope/IRAC




An international team of professional and amateur astronomers, which includes Alex Lobel, astronomer at the Royal Observatory of Belgium, has determined in detail how the temperature of four yellow hypergiants increases from 4000 degrees to 8000 degrees and back again in a few decades. They publish their findings in the professional journal Astronomy & Astrophysics.


The researchers analysed the light of four yellow hypergiants that has been observed on Earth over the past fifty to one hundred years. Yellow hypergiants are huge, luminous stars. They are fifteen to twenty times heavier than the Sun and shine 500,000 times brighter. The atmospheres of these stars can be so huge that, if they replaced our Sun, they would stretch beyond the orbit of Jupiter.


Because the researchers had such a long series of measurements, they could see in detail how the stars get warmer over decades and cool down in a few years.


The cycle begins with a cool star. In a few decades, the average atmospheric temperature increases to about 8000 degrees. At 8000 degrees, however, the atmosphere becomes unstable due to amplified pulsations. At a certain moment the entire atmosphere erupts. As a result, it cools down quickly and a self-accelerating process occurs in which electrons attach themselves to hydrogen ions and a lot of ionisation energy is released. This cools the atmosphere even further. The cooling from 8000 degrees to 4000 degrees takes only two years.


Then the cycle starts again from the beginning, only with a slightly less massive star. Eventually, astronomers think, the hypergiant transforms into a hotter star and ends its life as a supernova.


During the research, astronomers also found out that one of the four studied hypergiants was not as large as previously assumed. The star, HR5171A, turns out to be much closer than expected.





Contact:
 

Alex Lobel
E-mail: alex.lobel@oma.be
Phone number : +32(0)23730348
See also:
http://alobel.freeshell.org/hr5171.html


Article:


A.M. van Genderen  et al. (2019), Pulsations, eruptions and evolution of four yellow hypergiants. Accepted for public ation in Astronomy & Astrophysics:https://doi.org/10.1051/0004-6361/201834358. Free preprint: http://arxiv.org/abs/1910.02460



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2019 October 9 NGC 7714: Starburst after Galaxy Collision Image…


2019 October 9


NGC 7714: Starburst after Galaxy Collision
Image Credit: NASA, ESA, Hubble Legacy Archive;
Processing & Copyright: Rudy Pohl


Explanation: Is this galaxy jumping through a giant ring of stars? Probably not. Although the precise dynamics behind the featured image is yet unclear, what is clear is that the pictured galaxy, NGC 7714, has been stretched and distorted by a recent collision with a neighboring galaxy. This smaller neighbor, NGC 7715, situated off to the left of the featured frame, is thought to have charged right through NGC 7714. Observations indicate that the golden ring pictured is composed of millions of older Sun-like stars that are likely co-moving with the interior bluer stars. In contrast, the bright center of NGC 7714 appears to be undergoing a burst of new star formation. The featured image was captured by the Hubble Space Telescope. NGC 7714 is located about 130 million light years away toward the constellation of the Two Fish (Pisces). The interactions between these galaxies likely started about 150 million years ago and should continue for several hundred million years more, after which a single central galaxy may result.


∞ Source: apod.nasa.gov/apod/ap191009.html


Fluorite with Quartz | #Geology #GeologyPage…


Fluorite with Quartz | #Geology #GeologyPage #Minerals


Locality: Ehrenfriedersdorf, Erzgebirge, Saxony, Germany, Europe


Dimensions: 7.5 × 4.5 × 3.9 cm


Photo Copyright © Crystal Classics


Geology Page

www.geologypage.com — view on Instagram https://scontent.cdninstagram.com/vp/d0b58a78c6b8bf2b3c4f1373ee896c60/5E2DE653/t51.2885-15/e15/s640x640/72734927_236557167317721_5255328741975801066_n.jpg?_nc_ht=scontent.cdninstagram.com


2019 September 29 MyCn 18: The Engraved Hourglass Planetary…


2019 September 29


MyCn 18: The Engraved Hourglass Planetary Nebula
Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt


Explanation: Do you see the hourglass shape – or does it see you? If you can picture it, the rings of MyCn 18 trace the outline of an hourglass – although one with an unusual eye in its center. Either way, the sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a Sun-like star’s life occurs as its outer layers are ejected — its core becoming a cooling, fading white dwarf. In 1995, astronomers used the Hubble Space Telescope (HST) to make a series of images of planetary nebulae, including the one featured here. Pictured, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the hourglass. The unprecedented sharpness of the Hubble images has revealed surprising details of the nebula ejection process that are helping to resolve the outstanding mysteries of the complex shapes and symmetries of planetary nebulas like MyCn 18.


∞ Source: apod.nasa.gov/apod/ap190929.html


Using past extinctions to drive future conservation

Late Quaternary extinctions of large animals have historically been understood as global phenomena, resulting from climate fluctuations or quickly dispersing human populations. However, new technologies are enabling fine-grain analyses that shed new light on individual species’ varied responses to changing local conditions, new competitors and predators, and other external drivers. According to an interdisciplinary team writing in BioScience, the newly gained knowledge may be of particular value in understanding animal populations’ responses to contemporary threats, as well—in particular, those posed by climate change.











Using past extinctions to drive future conservation
The giant sloth eremotherium displayed at the Royal Ontarior Museum
[Credit: Brian Switek, Nat.Geographic]

Jillian A. Swift of the Bishop Museum and her coauthors focus on five key innovations—radiocarbon approaches, stable isotope analysis, ancient DNA, ancient proteomics, and microscopy—describing the ways in which new technologies are elucidating past extinctions. For instance, the authors describe the stable isotope analysis of a single tooth belonging to an extinct ground sloth from Belize. The data showed «how this individual varied its diet in response to seasonal fluctuations within a single year, granting high-resolution evidence for the ability of this species to adapt to climate-driven vegetation changes.»


Similarly, new methods may help in capturing the varied responses to changing conditions, some of which may be contrary to traditional expectations. The authors note that «bison (Bison priscus), wapiti (Cervus canadensis), and moose (Alces alces), increased in abundance before and during Late Pleistocene human colonization of Alaska and Yukon Territory in North America.»


Past responses to various disruptions are already informing present approaches to ecosystem management, say the authors. They highlight the work of Louys and colleagues, who drew on detailed histories of tropical megafauna and «evaluated the ranges and ecological roles of nine megafaunal taxa during the Pleistocene to assess their viability for rewilding efforts, including species translocations, reintroductions, or range expansion,» ultimately selecting orangutans, tapirs, and Tasmanian devils as the best suited to rewilding and ecosystem restoration in the Asia-Pacific region.


As perturbations grow in number and severity, say Swift and her colleagues, the «application of diverse methodologies to such records will only further the resolution of attempts to connect insights from the past to concerns in the present, enabling archaeology and paleontology to make a meaningful contribution to species and habitat protection or, where desired, reestablishment.»


Source: American Institute of Biological Sciences [October 02, 2019]



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Disappearing Peruvian glaciers

It is common knowledge that glaciers are melting in most areas across the globe. The speed at which tropical glaciers in the Peruvian Andes are retreating is particularly alarming, however. In the first detailed investigation of all Peruvian mountain ranges, a research team from Friedrich-Alexander-Universitat Erlangen-Nurnberg (FAU) has ascertained a drastic reduction of almost 30 percent in the area covered by glaciers between 2000 and 2016. The team also observed that El Nino activities had a significant effect on the state of the glaciers. Their results were published in the journal The Cryosphere.











Disappearing Peruvian glaciers
In certain mountain ranges in the Andes such as the Cordillera Blanca, glaciers are reported to have been retreating
at an accelerated rate since the 1980s. Ranrapalca (6163m) [Credit: Matthias Braun]

Tropical glaciers exist around the equator at altitudes of above 4000 metres. Peru is home to 92 percent of all areas covered by glaciers in the tropics. Due to their geographical location, tropical glaciers are particularly sensitive to fluctuations and changes in the climate. In certain mountain ranges in the Andes such as the Cordillera Blanca, glaciers are reported to have been retreating at an accelerated rate since the 1980s. Measurements of the mass balance of individual glaciers have also shown a significant loss of ice.


First region-wide measurements


Until now, there have not been any region-wide, uniform measurements of changes in mass and area of glaciers in Peru. A team of researchers led by Dr. Thorsten Seehaus, Institute of Geography at FAU, has worked together with colleagues from Peru to measure the changes in glaciers in the Peruvian Andes between 2000 and 2016 using satellite data.


The geographers charted the changes in glacier extent using Landsat images. They identified a glacial retreat of 29 percent during the period of investigation. A total of 170 of previously 1973 glaciers have even disappeared completely, an area roughly equivalent to 80,000 football pitches. Furthermore, they observed a rate of retreat for the period 2013 to 2016 almost four times higher than in the years before.











Disappearing Peruvian glaciers
Cordillera Apolobamba [Credit: Thorsten Seehaus]

The researchers also tracked changes in glacier volume and mass using satellite images. They used data from the joint German-American ‘Shuttle Radar Topography Mission’ from 2000 and the German TanDEM-X satellite which has been active since 2010. Over the entire period, they identified a loss of ice amounting to nearly eight gigatonnes. This is roughly equivalent to ten percent of the existing ice mass or a volume of water equivalent to roughly two cubic kilometres. The researchers observed that the rate of loss in ice mass after 2013 was approximately four times higher than in previous years.


The considerably higher rate of shrinkage in glaciers between 2013 and 2016, both in terms of area and mass, correlates with the intense El Nino activities experienced at that time, in other words unusual water currents in the equatorial Pacific. Typical climate variations triggered by El Nino in the Peruvian Andes are an increased temperature, a reduction in precipitation and a delayed rainy season. These factors lead to increased glacial melting and explain the greater rate of ice loss observed.


Glaciers as a source of water


Peru’s glaciers are a valuable source of water, as they store precipitation in the form of snow and ice and release it again in the form of meltwater during the dry season and drought periods. They have a valuable contribution to make in compensating for the dry periods and ensuring that rivers such as the Rio Santa in the Cordillera Blanca or the Rio Vilcanota-Urubamba in the region around Cusco continue to flow.











Disappearing Peruvian glaciers
Wamantay, Cordillera Vilcabamba [Credit: Thorsten Seehaus]

The supply of drinking water, irrigation of large-scale agricultural projects and hydroelectric power plants all depend on a continual and reliable supply of water. Glaciers can therefore be seen to play an important socio-economical role in the region. However, forecasts predict that the maximum amount of water which can be obtained from the melting of the glaciers has already been exceeded in certain areas of the Andes. An overall reduction in meltwater is to be expected.


Less ice, more natural hazards


The retreat of glaciers also increases the risk of natural hazards such as flood waves caused by glacial lake outburst floods. The melting of the glaciers leads to lakes being formed in areas which were previously covered by ice. The water is often held back by the former terminal moraines left by the glacier. If ice or rock avalanches end in the lake or the ice at the core of the moraines melts or erodes, the dam can break or overflow. This leads to the glacial lake emptying without warning, sending a destructive flood wave down the valley.


A flood wave such as this destroyed a third of the town of Huaraz in 1941. In the Cordillera Blanca, glacier-related natural disasters claimed more than 25,000 victims between 1941 and 2003. It follows that tracking changes in glaciers is also important from a civil protection point of view. Doing so allows countermeasures to be taken in good time, for example the reinforcement of dams or the controlled draining of water from glacial lakes.


The results of this study provide an important foundation for further, improved prognoses of how glaciers can be expected to develop, for national water management planning and global assessments of how glaciers are changing.


Source: University of Erlangen-Nuremberg [October 03, 2019]



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Ant-plant partnerships may play unexpected role in ant evolution

Partnerships between ant and plant species appear to arise from—but not drive—rapid diversification of ants into new species. Katrina Kaur of the University of Toronto, Canada, and colleagues present these findings in PLOS Computational Biology.











Ant-plant partnerships may play unexpected role in ant evolution
The Amazonian ant, Allomerus octoarticulatus, protects its host plant, Cordia nodosa, against the plant’s enemies.
This ant species is one of over 400 mutualistic ant species in a new database that was assembled
by text-mining the ecological literature [Credit: Christopher Reid, University of Toronto]

Some plants and ants have mutually beneficial, or «mutualistic,» interactions: plants provide ants with food or shelter, while ants protect plants against herbivores or disperse their seeds. Previous research has shown that plants with ant partners diversify faster—showing a bigger net difference between extinction rates and the rise of new plant species—than do other plants.


Kaur and colleagues wondered if plants affect ant evolution similarly. However, the data they needed was buried in thousands of scientific papers each discussing just one or a few ant species. So, they wrote a computer program to «read» and extract data from over 89,000 paper abstracts, successfully assembling a large database of ant ecological interactions. Then, they mapped the data onto an ant evolutionary tree and modeled how partnering with plants has affected ant diversification.


The analysis produced unexpected results. The researchers hypothesized that ants would first evolve mutualism with plants and then diversify, but their model suggests the opposite: ants that are already rapidly diversifying are more likely to evolve a plant partnership. Once they do, their diversification rates slow.


«To our surprise, the intimate and often beneficial relationships that ants have with plants apparently did not help to generate the over 14,000 ant species on Earth today,» Kaur says. «Mutualism may put the brakes on the rise of new species or increase the threat of extinction because an ant’s fate becomes linked to its plant partner’s.»


The researchers plan to use their «text-mining» computer program to assemble an even larger database from thousands of additional papers in order to understand why ant-plant partnerships have different effects on ant versus plant evolution. A similar approach could also reveal insights about other species in mutualistic relationships, such as seed-dispersing birds or human gut microbes.


Source: Public Library of Science [October 03, 2019]



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Was early stick insect evolution triggered by birds and mammals?

Stick and leaf insects are a diverse and strikingly bizarre group of insects with a world-wide distribution, which are more common in tropical and subtropical areas. They are famous for their impressively large body size, compared to other insects, and their remarkable ability to camouflage themselves as twigs, leaves or bark in order to hide from potential predators. A team of international researchers led by the University of Gottingen has now generated the first phylogenomic tree of these insects.











Was early stick insect evolution triggered by birds and mammals?
Stick insect relatives: different in appearance but of the same origin. Surprisingly, New World (above) and Old World
stick insects (below) form their own evolutionary lines within this insect group, as a new genomic study shows. From
top left to bottom right: pair of Mexican stick insects Pseudosermyle phalangiphora, female of Metriophasma diocles
from Panama, pair of Black Velvet stick insects Peruphasma schultei from Peru, female of Australian Giant Prickly
stick insect Extatosoma tiaratum, female of Indian stick insect Carausius morosus, a pair of «tree lobster»
stick insects Eurycantha calcarata from New Guinea [Credit: Christoph Seiler]

«Previously the relationships between stick insects were inferred based on just a handful of genes. This is the first study in which more than 2,000 genes were analysed for each species,» explains Dr Sven Bradler from the University of Gottingen and senior author of the study. 38 species of stick and leaf insects from all over the world were investigated by the researchers of the 1KITE project (1,000 Insect Transcriptome Evolution). «Previous studies were unable to explain the early evolution of these insects. This has now changed with the new and much more extensive dataset that can even reconstruct the origin of the oldest lineages,» adds Dr Sabrina Simon, first author of this study from the University Wageningen.


The most surprising finding is that the relationships between the early emerging groups of stick and leaf insects largely disprove the earlier assumptions. In fact, the genealogy reflects more the geographic distribution than the anatomical similarity of the animals. The authors revealed a New World lineage of purely North and South American species and a group of Old World origin that comprises species from Africa to New Zealand.


The biogeographic history was reconstructed by Sarah Bank, PhD student at the University of Gottingen and coauthor of the study, which resulted in further unexpected results: «The flamboyant stick insects of Madagascar, for instance, descended from a single ancestral species who colonised the island approximately 45 million years ago.»


The age estimation of the phylogenetic tree suggests that most of the old lineages emerged after the dinosaurs became extinct 66 million years ago. Thus, the remarkable camouflage of stick and leaf insects most probably evolved afterwards as adaptation against predatory mammals and birds.


«Stick insects become more and more important as model organisms for evolutionary research. The new comprehensive molecular dataset won’t be exhaustively analysed for quite some time and will provide exciting insights into the function of the numerous detected genes,» explains Bradler with regard to future studies.


The study has been published in the journal Frontiers in Ecology and Evolution.


Source: University of Gottingen [October 07, 2019]



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Scientists uncover genetic similarities among species that use sound to navigate

Evolutionary adaptations like echolocation that are shared by unrelated species arose in part due to identical, independently acquired genetic changes, according to a new Stanford study of whole genome sequences.











Scientists uncover genetic similarities among species that use sound to navigate
Many bats use echolocation, but so do dolphins. Evolutionary adaptations that are shared by unrelated species
arose in part due to identical, independently acquired genetic changes, a study found
[Credit: Rudmer Zwerver/Shutterstock]

Insect-eating bats navigate effortlessly in the dark and dolphins and killer whales gobble up prey in murky waters thanks in part to specific changes in a set of 18 genes involved in the development of the cochlear ganglion—a group of nerves that transmit sound from the ear to the brain, according to a study by researchers at Stanford University.


Surprisingly, these very different species evolved their unique ability to use sound waves to navigate and identify obstacles and tasty morsels, be they mosquito or minnow, in part by acquiring identical mutations in their genomes—mutations not shared by other, more closely related species like humpback whales, which patiently sieve the ocean for krill, or fruit bats, which seek stationary, yummy-smelling snacks.


The discovery solves a long-standing biological debate as to whether echolocating bats and whales have independently undergone many similar genomic changes «under the hood» to accomplish the same goal. It also opens the door to understanding more about the molecular basis for human disorders as varied as deafness, skin lesions caused by high cholesterol, and altitude sickness, the researchers said.


«Not only is it breathtaking to see how these very different species carved their own evolutionary niches for themselves through independently acquiring similar genetic changes, it’s beneficial to our understanding of our own physiology and development,» said Gill Bejerano, Ph.D., professor of developmental biology, of computer science, of pediatrics and of biomedical data science at Stanford. «Developmental biologists have long wondered whether, at the most basic level, something that’s the same on the outside—like species that use echolocation—are the same on the inside. That is, do they acquire these traits through similar molecular changes? Now we know that not only is this true as least some of the times, but also that many of these changes occur in the coding region of the genome. It’s fascinating.»


Bejerano is the senior author of the study, which was published in the Proceedings of the National Academy of Sciences. Postdoctoral scholar Amir Marcovitz, Ph.D., and graduate students Yatish Turakhia and Heidi Chen share lead authorship.


Although the cochlear ganglion has been previously implicated in the sound-as-GPS technique known as echolocation, past studies have relied primarily on researchers’ intuition to identify possible genetic players based on prior knowledge of their function—a kind of looking-for-your-lost-keys-under-a-lamppost approach. These studies suggested only a few responsible mutations in just four genes involved in hearing.


Sifting through whole genomes


In contrast, the Stanford researchers developed an unbiased way to sift through whole genome sequences and spotlight concerted genetic changes shared by animals with unusual abilities or traits.


They used the technique to identify genes involved not only in echolocation, but also others critical to the development of the specialized skin of aquatic mammals such as manatees and killer whales, or to the increased lung capacity and function enjoyed by jaunty high-altitude animals like pikas and alpacas.


The technique developed by the researchers is likely to open countless doors for biologists seeking to identify the genetic underpinnings of other adaptive traits. The findings also answer yet another hotly debated question in developmental biology.


«For a long time, biologists have wondered whether important evolutionary changes could occur through changes in the sequences of genes that are very similar across related species,» Bejerano said. «These genes often control multiple functions in different tissues throughout the body, so it seems it would be very difficult to introduce even minor changes. But here we’ve found that not only do these very different species share specific genetic changes, but also that these changes occur in coding genes.»


Bejerano and his colleagues developed the technique by searching for instances in which animals sharing unique traits also shared changes in their DNA that are not found in their more closely related peers. To analyze the evolution of echolocation, for example, they compared the genetic sequences of echolocating bats with those of megabats that don’t echolocate, and toothed cetaceans such as dolphins and killer whales with cloven-hooved land mammals. (At the time of the study, whole genome sequences for nonecholocating whales were not available.)


The researchers looked for instances in which the DNA sequences of genes independently changed to encode amino acids that, although identical among echolocating species, differed from the amino acid found at that position in most other mammals.


They then devised a way to determine whether these changes occurred more often than would be expected by chance in particular groups of genes that are predicted to have similar functions. There are about 4,000 groups of genes known to affect the development and function of a large variety of tissues in mammals.


Remarkably, the researchers found that their unbiased analysis homed in on the cochlear ganglion as the single most affected tissue among echolocating mammals. In particular, 25 «convergent» amino acid changes occurred in 18 genes known to be involved in the development of the cochlear ganglion. Only two of the 25 changes had been previously identified in past echolocation studies.


«Pulling the cochlear ganglion—a real poster child for the development of echolocation—out of a hat containing more than 4,000 possible gene sets, based on genomic sequence alone, was pretty spectacular,» Bejerano said. «You go from agnostically checking all these different groups to boom, you have a prime suspect jump immediately to the top.»


Burrowing more deeply into data


Finally, the scientists burrowed more deeply into the data to ensure that their tool wouldn’t mistakenly identify instances in which different animals had devolved, or abandoned certain traits when they were no longer required by their environment. To do so they examined the whole genome sequences of different subterranean moles that have lost their vision after millennia in the dark underground.


«This study is a great example of what we can accomplish when we combine the data in whole genome sequences from multiple species with functional information about specific genes,» Bejerano said. «The biomedical community has been gathering both of these datasets for many years, and it’s wonderful to now be at the confluence of these two fields—identifying the relationships between gene conservation and function and between phenotype and gene sequences. Now we’ve developed a tool that can screen millions of potential matches, and we are seeing the emergence of some beautiful patterns. Doing this in other animals and for other traits is going to be so much fun.»


Author: Krista Conger | Source: Stanford University Medical Center [October 04, 2019]



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Archaea hold clues to ancient ocean temperatures

Solving a decades-old mystery, Stanford researchers have discovered proteins that enable hardy microbes called archaea to toughen up their membranes when waters are overly warm. Finding these proteins could help scientists piece together the state of Earth’s climate going back millions of years to when those archaea were cruising the ancient oceans.











Archaea hold clues to ancient ocean temperatures
This image shows a cell of archaea Sulfolobus tengchongensis under a microscope that has been
 infected by viruses. New research identifies proteins in this group of archaea that could
help gauge ancient ocean temperatures [Credit: Xiangyux/WikiCommons]

«People have been looking for these proteins for 40 years,» said Paula Welander, an associate professor of Earth system science in Stanford University’s School of Earth, Energy & Environmental Sciences (Stanford Earth), and lead author of a study describing the finding published in Proceedings of the National Academy of Sciences.


With this finding scientists can more accurately use the lipids — or fats — found in archaeal membranes and preserved in the ocean’s sediments to estimate historic ocean temperatures, Welander said.


Battening down the hatches


When under stress, archaea fuse their usually double-layered cell membranes into a single layer. Battening down the hatches in this manner firms up the membranes, which, being mostly made of fat, can get too floppy when the temperature spikes — like butter left on a kitchen counter.


Some archaea further modify the structures that fuse their membrane layers by adding on ring-like pieces that make the membranes even more compact and sturdy. These adaptations are helpful from a climatology perspective, since the membrane-linking structures — along with those sets of rings — readily preserve in marine sediments. By examining the numbers and kinds of rings, climate scientists can gauge surface water temperatures where and when those archaea lived. This technique has been used as evidence of the warmer seas of the Jurassic era, dating back more than 150 million years to the heyday of the dinosaurs.


Finding the proteins involved in making those structures resolves some uncertainties scientists have had about inferring ancient temperatures from archaeal lipids — what they call the paleotemperature proxies.


Climatologists have presumed that a single group of archaea, the Thaumarchaeota, are responsible for making lipids with rings found in open oceans and that they add those rings in response to water temperature changes. But if other environmental factors such as salinity and acidity trigger ring production in other marine archaeal groups, that could scramble how they read the temperature signals.


According to the new study, climatologists can breathe a sigh of relief. By finally nailing down the proteins in play, the Stanford researchers show that Thaumarchaeota are indeed the dominant source of the ring-bearing membrane structures in ocean waters, supporting previous ideas of ancient sea surface temperatures.


«With that critical information now in hand, we can start to constrain some of the uncertainty about this particular archaea-based paleotemperature proxy,» Welander said.


Pursuing the proteins


Although not identified until the late 1970s, archaea have since been recognized as constituting a whole new third domain of life, alongside the more-familiar bacteria and eukaryotes — multicellular organisms, including humans. Although archaea superficially resemble bacteria, biochemical and reproductive differences testify to their uniqueness. Many archaea are also extremophiles, which thrive in austere environments like hot springs where other life cannot survive.


To find the ring-making proteins, the Stanford team experimented with Sulfolobus acidocaldarius, among the least difficult archaea to grow and manipulate in a lab.


«This organism is one of the very few archaea that has a genetic system where we can do the kind of work we like to do,» Welander said.


Her team set out to find which proteins enabled S. acidocaldarius to attach rings to its membrane-spanning structures. The researchers first found three possible genes by looking across the genomes of archaea that do and don’t construct rings. They then created mutants in the lab lacking one, two or all three genes and, ultimately, two of these genes proved integral to the ring structures.


Those genes failed to turn up in another group of archaea that share marine environments with Thaumarchaeota and were considered as a possible, additional source of ringed structures in sediment samples. With that contribution ruled out, the sea temperature estimates derived from the paleotemperature proxy in question look more robust.


Taking it global


Welander said that scientists can now look into extending the Stanford team’s findings into well-sampled marine regions worldwide. Her team picked through a genetic dataset from the north Pacific Ocean, and it therefore only directly speaks to that particular biome. Other datasets from the Atlantic Ocean and the Mediterranean Sea, for example, should reveal if Thaumarchaeota are also responsible for laying down the molecular fossils of interest in those areas. These paleotemperature proxies could even be extended into lakes and other environments, Welander said, opening up still more pages in Earth’s climate chronicles.


Going beyond the climatological aspects of the findings, Welander noted that figuring out how the archaeal proteins handle the arcane work of membrane fusing could reveal compelling new biochemistry for potential real-world applications, such as drug discovery and materials science.


«Microbes invent all kinds of weird biochemistry to do all kinds of weird reactions,» Welander said. «Anytime you can expand that chemistry of what is possible, it’s really exciting from just a basic science perspective.»


Author: Adam Hadhazy | Source: Stanford University [October 07, 2019]



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Amethyst with Marcasite | #Geology #GeologyPage…


Amethyst with Marcasite | #Geology #GeologyPage #Minerals


Locality: Boldut Mine, Cavnic, Maramures Co, Romania, Europe


Dimensions: 11.2 × 7.9 × 5.7 cm


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9th Century CE Beehive Hut Reconstruction, Kilmartin Museum, Argyll, 28.9.19.




9th Century CE Beehive Hut Reconstruction, Kilmartin Museum, Argyll, 28.9.19.


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Prehistoric Pottery, Kilmartin Museum, Argyll, 28.9.19.







Prehistoric Pottery, Kilmartin Museum, Argyll, 28.9.19.


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Argyll Prehistoric Treasures, Kilmartin Museum, Kilmartin Glen, Argyll, 28.9.19.









Argyll Prehistoric Treasures, Kilmartin Museum, Kilmartin Glen, Argyll, 28.9.19.


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The last mammoths died on a remote island

The last woolly mammoths lived on Wrangel Island in the Arctic Ocean; they died out 4,000 years ago within a very short time. An international research team from the Universities of Helsinki and Tubingen and the Russian Academy of Sciences has now reconstructed the scenario that could have led to the mammoths’ extinction. The researchers believe a combination of isolated habitat and extreme weather events, and even the spread of prehistoric man may have sealed the ancient giants’ fate. The study has been published in the latest edition of Quaternary Science Reviews.











The last mammoths died on a remote island
This is a mammoth tooth on the riverbank on Wrangel Island
[Credit: Juha Karhu]

During the last ice age — some 100,000 to 15,000 years ago — mammoths were widespread in the northern hemisphere from Spain to Alaska. Due to the global warming that began 15,000 years ago, their habitat in Northern Siberia and Alaska shrank. On Wrangel Island, some mammoths were cut off from the mainland by rising sea levels; that population survived another 7000 years.


The team of researchers from Finland, Germany and Russia examined the isotope compositions of carbon, nitrogen, sulfur and strontium from a large set of mammoth bones and teeth from Northern Siberia, Alaska, the Yukon, and Wrangel Island, ranging from 40,000 to 4,000 years in age. The aim was to document possible changes in the diet of the mammoths and their habitat and find evidence of a disturbance in their environment. The results showed that Wrangel Island mammoths’ collagen carbon and nitrogen isotope compositions did not shift as the climate warmed up some 10,000 years ago. The values remained unchanged until the mammoths disappeared, seemingly from the midst of stable, favorable living conditions.


This result contrasts with the findings on woolly mammoths from the Ukrainian-Russian plains, which died out 15,000 years ago, and on the mammoths of St. Paul Island in Alaska, who disappeared 5,600 years ago. In both cases, the last representatives of these populations showed significant changes in their isotopic composition, indicating changes in their environment shortly before they became locally extinct.


Earlier aDNA studies indicate that the Wrangel Island mammoths suffered mutations affecting their fat metabolism. In this study, the team found an intriguing difference between the Wrangel Island mammoths and their ice age Siberian predecessors: the carbonate carbon isotope values indicated a difference in the fats and carbohydrates in the populations’ diets. «We think this reflects the tendency of Siberian mammoths to rely on their reserves of fat to survive through the extremely harsh ice age winters, while Wrangel mammoths, living in milder conditions, simply didn’t need to», says Dr. Laura Arppe from the Finnish Museum of Natural History Luomus, University of Helsinki, who led the team of researchers. The bones also contained levels of sulfur and strontium that suggested the weathering of bedrock intensified toward the end of the mammoth population’s existence. This may have affected the quality of the mammoths’ drinking water.


Why then did the last woolly mammoths disappear so suddenly? The researchers suspect that they died out due to short-term events. Extreme weather such as a rain-on-snow, i.e. an icing event could have covered the ground in a thick layer of ice, preventing the animals from finding enough food. That could have led to a dramatic population decline and eventually to extinction. «It’s easy to imagine that the population, perhaps already weakened by genetic deterioration and drinking water quality issues could have succumbed after something like an extreme weather event,» says professor Herve Bocherens from the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tubingen, a co-author of the study.


Another possible factor could have been the spread of humans. The earliest archaeological evidence of humans on Wrangel Island dates to just a few hundred years after the most recent mammoth bone. The chance of finding evidence that humans hunted Wrangel Island mammoths is very small. Yet a human contribution to the extinction cannot be ruled out.


The study shows how isolated small populations of large mammals are particularly at risk of extinction due to extreme environmental influences and human behavior. An important takeaway from this is that we can help preserve species by protecting the populations that are not isolated from one another.


Source: University of Helsinki [October 07, 2019]



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Early humans evolved in ecosystems unlike any found today

To understand the environmental pressures that shaped human evolution, scientists must first piece together the details of the ancient plant and animal communities that our fossil ancestors lived in over the past 7 million years. Because putting together the puzzle of millions-of-years-old ecosystems is a difficult task, many studies have reconstructed the environments by drawing analogies with present-day African ecosystems, such as the Serengeti. A study led by a University of Utah scientist calls into question such approaches and suggests that the vast majority of human evolution occurred in ecosystems unlike any found today. The paper was published in the Proceedings of the National Academy of Sciences.











Early humans evolved in ecosystems unlike any found today
Artist Heinrich Harder’s illustration of the extinct Deinotherium, an ancient relative to modern-day elephants that
appeared in the Middle Miocene 20 million years ago and lived until the Early Pleistocene, around 2 million
 years ago. Harder completed the illustration in the early 1900s using fossils as his model
[Credit: Heinrich Harder]

To test for differences between modern and ancient environments, the researchers analyzed a dataset of more than 200 present-day African mammal communities and more than 100 fossil communities spanning the past 7 million years in eastern Africa, a time period encompassing all of human evolution. They found that prior to 700,000 years ago, mammal communities looked far different from those today. For example, fossil communities supported a greater diversity of megaherbivores, species over 2,000 pounds, such as elephants.
Likewise, the dietary structure of fossil communities frequently departed from those seen today, with patterns of grass- and leaf-eating species fluctuating in abundance. Around 1 million years ago, fossil communities began transitioning to a more modern makeup, which the authors suggest is the likely the outcome of long-term grassland expansion coupled with arid climate pulses. The new paper adds to growing evidence that scientists need to critically re-evaluate our understanding of the ancient ecosystems in which early humans evolved.


«For a long time, our field has been trying to pin down how environmental changes influenced human evolution, but we’ve got to be able to reconstruct past environments right in the first place,» said lead author Tyler Faith, curator of archaeology at the Natural History Museum of Utah and assistant professor of anthropology at the U. «If we continue to reconstruct ancient environments on the basis of modern African ecosystems, we are likely missing an entire realm of possibilities in how past ecosystems functioned. Our study invites our fellow researchers to think more critically about that.»


Linking changes in mammal communities to ecosystem functions


Eastern Africa is a boon for mammal fossils, making it an ideal region to piece together ancient ecosystems over the past 7 million years. With their extensive database of both ancient and modern mammal communities, the researchers focused on three traits: diet, body size, and digestive strategy. For all of these traits, they found that the makeup of ancient herbivore communities differed significantly from those of today. This is key, as herbivores directly shape the structure of ecosystems in ways that impact a wide variety of animal and plant species.


«Large herbivores aren’t just passive parts of an ecosystem, we know that they can shape the landscape. They’re eating the plants, and the biggest ones are knocking down trees or trampling soils, which collectively influences vegetation structure, fire regimes, nutrient cycling, and impacts other organisms, including humans,» said Faith.











Early humans evolved in ecosystems unlike any found today
The geographic distribution of the modern (left) and fossil (right) larger herbivore
 communities analyzed in the paper [Credit: Faith et. al., 2019]

For example, modern African ecosystems are dominated by ruminants—relatives of cows and antelopes that have four compartments in their stomachs to thoroughly break down food. Non-ruminants equipped with simple stomachs are comparatively rare, with at most eight species coexisting in the same area today. Non-ruminants, including relatives of elephants, zebras, hippos, rhinos and pigs, are like digestive conveyor belts, said Faith. They eat larger quantities of plants to make up for their inefficient digestion. In contrast to the present-day pattern, eastern African fossil records document landscapes rich in non-ruminant communities, with dozens of species co-existing within the same area.
Fossil and modern communities were also vastly different in terms of body sizes. The fossil records document lots more megaherbivores than their modern counterparts. A steady decline of megaherbivores began 4.5 million years ago until they represented a more modern distribution 700,000 years ago.


What is the impact of these eating machines all living together in the same places, when it’s not the case today?


«These ancient herbivore communities were probably consuming far more vegetation, which means less fuel for wildfires. Because fire is an important part of modern ecosystems in Africa and favors grasslands over woodlands, it’s going to fundamentally alter how things are working at the level of entire ecosystems, starting with the plant communities,» adds John Rowan, co-author and postdoctoral researcher at the University of Massachusetts Amherst. «Paleontologists have been aware of that, but until now, no one’s really tried to measure just how different the past was compared to the present.»


Drying climate and grasslands drive a shift


What drove shifts in mammal communities over the past 7 million years? One of the most well-documented changes is the expansion of grasslands throughout the past 4 million years. Many of the fossil megaherbivores preferred wooded environments, whereas ruminants thrive in the wide-open savannas that dominate parts of eastern Africa today. The fossil record of herbivores closely follows the shifting environments, with changes in the representation of these groups tracking long-term grassland expansion.











Early humans evolved in ecosystems unlike any found today
A comparative analysis of fossil (gray shaded) and modern (light gray shaded) mammal communities.
The study found little overlap between the types of mammals that thrived in the past versus
in modern East African ecosystems [Credit: Faith et. al., 2019]

Around 1 million years ago, fossils show a shift in mammal community dietary structure that grassland expansion alone fails to explain. The non-ruminants that had dominated eastern African ecosystems fell into a sharp decline. This corresponds to marine dust records suggesting the region experienced pulses of climate drying that would have hit non-ruminants especially hard because they depend on reliable access to surface water, meaning that many species may have disappeared alongside the rivers and lakes they depended on. Additionally, the conveyor belt eating strategy of non-ruminants relies on accessing abundant vegetation, which would have declined during periods of drought.


Looking forward


The authors do not fault previous researchers for relying so heavily on analogies with present-day African ecosystems, emphasizing that a study of this scope has only recently become possible.


«Paleontology has hit a big data era,» said Faith. Co-author and Colorado State University assistant professor Andrew Du added, «With the assembly of large, comprehensive datasets, we can now ask important questions that are fundamentally different from those asked in the past. We can investigate larger-scale patterns and dynamics that undoubtedly influenced the course of human evolution.»


Source: University of Utah [October 07, 2019]



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