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Showing posts with label Archeology and Paleontology. Show all posts
Showing posts with label Archeology and Paleontology. Show all posts

Sunday, 12 April 2020

Prehistory Shares Its Secrets Thanks to New Dating Method


A team at the University of Bristol has developed a new method of dating pottery which is allowing archaeologists to date prehistoric finds from across the world with remarkable accuracy.

The exciting new method, reported in detail today in the journal Nature, is now being used to date pottery from a range of key sites up to 8,000 years old in Britain, Europe and Africa.

Archaeological pottery has been used to date archaeological sites for more than a century, and from the Roman period onwards can offer quite precise dating.  But further back in time, for example at the prehistoric sites of the earliest Neolithic farmers, accurate dating becomes more difficult because the kinds of pottery are often less distinctive and there are no coins or historical records to give context.

This is where radiocarbon dating, also known as 14C-dating, comes to the rescue. Until now, archaeologists had to radiocarbon date bones or other organic materials buried with the pots to understand their age. But the best and most accurate way to date pots would be to date them directly, which the University of Bristol team has now introduced by dating the fatty acids left behind from food preparation.



Professor Richard Evershed from the University of Bristol’s School of Chemistry led the team. He said: “Being able to directly date archaeological pots is one of the “Holy Grails” of archaeology. This new method is based on an idea I had going back more than 20 years and it is now allowing the community to better understand key archaeological sites across the world.

“We made several earlier attempts to get the method right, but it wasn’t until we established our own radiocarbon facility in Bristol that we cracked it. There’s a particular beauty in the way these new technologies came together to make this important work possible and now archaeological questions that are currently very difficult to resolve could be answered.”

The trick was isolating individual fat compounds from food residues, perhaps left by cooking meat or milk, protected within the pores of prehistoric cooking pots. The team brought together the latest high resolution nuclear magnetic resonance spectroscopy and mass spectrometry technologies to design a new way of isolating the fatty acids and checking they were pure enough for accurate dating.

The team then had to show that the new approach gave dates as accurate as those given by materials commonly dated in archaeology, such as bones, seeds and wood. To do this the team looked at fat extracts from ancient pottery at a range of key sites in Britain, Europe and Africa with already precise dating which were up to 8,000 years old.



From the famous Sweet Track site in Somerset and several sites in the Alsace region of France, to the World Heritage site of Çatalhöyük in central Turkey and the famous rock shelter site of Takarkori in Saharan Africa, the new method was proven to date sites incredibly accurately, even to within a human life span.

Professor Alex Bayliss, Head of Scientific Dating at Historic England, who undertook the statistical analyses, added: “It is very difficult to overstate the importance of this advance to the archaeological community. Pottery typology is the most widely used dating technique in the discipline, and so the opportunity to place different kinds of pottery in calendar time much more securely will be of great practical significance.”

In London, England, the new dating method has been used on a remarkable collection of pottery found in Shoreditch, thought to be the most significant group of Early Neolithic pottery ever found in the capital. The extraordinary trove, comprising 436 fragments from at least 24 separate vessels weighing nearly 6.5 kilos in total, was discovered by archaeologists from MOLA (Museum of London Archaeology).

The site appeared to date from the time when the first farmers came to Britain but accurately dating it was difficult until the Bristol team, using their new dating method on traces of milk fats extracted from the pots, showed the pottery was 5,500 years old. The team were able to date the pottery collection to a window of just 138 years, to around 3600BC.

The results indicate that around 5600 years ago the area around what is now Shoreditch High Street was used by established farmers who ate cow, sheep or goat dairy products as a central part of their diet. These people were likely to have been linked to the migrant groups who were the first to introduce farming to Britain from Continental Europe around 4000 BC – just 400 years earlier.



Jon Cotton, a consultant prehistorian working for MOLA, said: “This remarkable collection helps to fill a critical gap in London’s prehistory. Archaeological evidence for the period after farming arrived in Britain rarely survives in the capital, let alone still in-situ. This is the strongest evidence yet that people in the area later occupied by the city and its immediate hinterland were living a less mobile, farming-based lifestyle during the Early Neolithic period.”

The results from this site are a prime example of where pottery survives in circumstances that other organic materials do not, so using this revolutionary new method will unlock important information about our prehistoric past.


Bibliography:

Emmanuelle Casanova, Timothy D. J. Knowles, Alex Bayliss, Julie Dunne, Marek Z. Barański, Anthony Denaire, Philippe Lefranc, Savino di Lernia, Mélanie Roffet-Salque, Jessica Smyth, Alistair Barclay, Toby Gillard, Erich Claßen, Bryony Coles, Michael Ilett, Christian Jeunesse, Marta Krueger, Arkadiusz Marciniak, Steve Minnitt, Rocco Rotunno, Pieter van de Velde, Ivo van Wijk, Jonathan Cotton, Andy Daykin, Richard P. Evershed.

Accurate compound-specific 14C dating of archaeological pottery vessels.

Nature, 2020; DOI: 10.1038/s41586-020-2178-z.

Saturday, 11 April 2020

Synchrotron X-ray sheds light on some of the world's oldest dinosaur eggs


An international team of scientists led by the University of the Witwatersrand in South Africa, has been able to reconstruct, in the smallest details, the skulls of some of the world's oldest known dinosaur embryos in 3D, using powerful and non-destructive synchrotron techniques at the ESRF, the European Synchrotron in France. They found that the skulls develop in the same order as those of today's crocodiles, chickens, turtles and lizards. The findings are published today in Scientific Reports.

University of the Witwatersrand scientists publish 3D reconstructions of the ~2cm-long skulls of some of the world's oldest dinosaur embryos in an article in Scientific Reports. The embryos, found in 1976 in Golden Gate Highlands National Park (Free State Province, South Africa) belong to South Africa's iconic dinosaur Massospondylus carinatus, a 5-meter long herbivore that nested in the Free State region 200 million years ago.

The scientific usefulness of the embryos was previously limited by their extremely fragile nature and tiny size. In 2015, scientists Kimi Chapelle and Jonah Choiniere, from the University of Witwatersrand, brought them to the European Synchrotron (ESRF) in Grenoble, France for scanning. At the ESRF, an 844 metre-ring of electrons travelling at the speed of light emits high-powered X-ray beams that can be used to non-destructively scan matter, including fossils. The embryos were scanned at an unprecedented level of detail -- at the resolution of an individual bone cell. With these data in hand, and after nearly 3 years of data processing at Wits' laboratory, the team was able to reconstruct a 3D model of the baby dinosaur skull. "No lab CT scanner in the world can generate these kinds of data," said Vincent Fernandez, one of the co-authors and scientist at the Natural History Museum in London (UK). "Only with a huge facility like the ESRF can we unlock the hidden potential of our most exciting fossils. This research is a great example of a global collaboration between Europe and the South African National Research Foundation," he adds.



Up until now, it was believed that the embryos in those eggs had died just before hatching. However, during the study, lead author Chapelle noticed similarities with the developing embryos of living dinosaur relatives (crocodiles, chickens, turtles, and lizards). By comparing which bones of the skull were present at different stages of their embryonic development, Chapelle and co-authors can now show that the Massospondylus embryos were actually much younger than previously thought and were only at 60% through their incubation period.

The team also found that each embryo had two types of teeth preserved in its developing jaws. One set was made up of very simple triangular teeth that would have been resorbed or shed before hatching, just like geckos and crocodiles today. The second set were very similar to those of adults, and would be the ones that the embryos hatched with. "I was really surprised to find that these embryos not only had teeth, but had two types of teeth. The teeth are so tiny; they range from 0.4 to 0.7mm wide. That's smaller than the tip of a toothpick!," explains Chapelle.

The conclusion of this research is that dinosaurs developed in the egg just like their reptilian relatives, whose embryonic developmental pattern hasn't changed in 200 million years. "It's incredible that in more than 250 million years of reptile evolution, the way the skull develops in the egg remains more or less the same. Goes to show -- you don't mess with a good thing!," concludes Jonah Choiniere, professor at the University of Witwatersrand and also co-author of the study.

The team hopes to apply their method to other dinosaur embryos to estimate their level of development. They will be looking at the rest of the skeleton of the Massospondylus embryos to see if it also shares similarities in development with today's dinosaur relatives. The arms and legs of the Massospondylus embryos have already been used to show that hatchlings likely walked on two legs.

Main findings:




  • High powered X-rays were used to reconstruct the skulls of some of the world's oldest known dinosaur embryos.




  • The skull could be seen in 3D at an unprecedented level of detail.




  • Dinosaur embryo skulls appear to develop in the same order as those of today's crocodiles, chickens, turtles and lizards.




  • These dinosaur embryos appear to have been fossilised at approximately 60% through their incubation period. This is much earlier than previously thought.




  • The dinosaur embryos have two types of teeth that range in size from 0.4 to 0.7mm wide. One of these sets would have been shed or resorbed before hatching.







  • Bibliography:

    Kimberley E. J. Chapelle, Vincent Fernandez, Jonah N. Choiniere. Conserved in-ovo cranial ossification sequences of extant saurians allow estimation of embryonic dinosaur developmental stages. Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-60292-z


    Kimberley E. J. Chapelle, Roger B. J. Benson, Josef Stiegler, Alejandro Otero, Qi Zhao, Jonah N. Choiniere. A quantitative method for inferring locomotory shifts in amniotes during ontogeny, its application to dinosaurs and its bearing on the evolution of posture. Palaeontology, 2020; 63 (2): 229 DOI: 10.1111/pala.12451

    Monday, 6 April 2020

    Tooth be told: Earless seals existed in ancient Australia


    A fossilised seal tooth found on a Victorian beach could hold the key to uncovering the history and geography of earless seals that graced Australia's shores three million years ago.

    This prehistoric specimen is only the second earless seal fossil ever discovered in Australia, and proves the country's local fur seals and sea lions were preceded by a group of sea mammals, known as monachines, now long extinct in Australia.

    The study also highlights the current dangers of climate change to Earth's existing wildlife, with falling sea levels likely to have played a role in the extinction of these ancient seals.

    The history of this rare specimen was published today (Friday 3 April) in the Journal of Vertebrate Paleontology by a team of scientists from Monash University's School of Biological Sciences and Department of Anatomy and Developmental Biology, and Museums Victoria, led by PhD candidate James Rule.

    "This tooth, roughly three million years old, tells a story similar to what occurred in South Africa and South America in the past. Earless monachine seals used to dominate southern beaches and waters, and then suddenly disappeared, with eared seals replacing them," Mr Rule said.

    "Since seal fossils are rare globally, this discovery makes a vital contribution to our understanding of this iconic group of sea mammals."



    An Australian citizen scientist and amateur fossil collector discovered the tooth while strolling along the beach at Portland, western Victoria.

    But it wasn't until he donated the fossil to Museums Victoria many years later that it was found to have been a tooth from an extinct group of earless seals.

    The research team compared the tooth to other pinnipeds -- a group that includes earless seals, fur seals, sea lions and the walrus.

    They found the tooth possessed characteristics of monachines and shed light on how these seals lived and what they ate.

    "This seal lived in shallow waters close to the shore, likely hunting fish and squid. As monachines cannot use their limbs to walk on land, it would have required flat, sandy beaches when it came ashore to rest," Mr Rule said.

    Researchers believe drastic changes in the Earth's climate fundamentally altered Australia's environment by eliminating the beaches used by earless seals to rest.

    "These changes in the past have led to the extinction of Australia's ancient earless seals," Dr David Hocking, co-author and Research Fellow in Monash University's School of Biological Sciences, said.



    "Our living fur seals and sea lions will likely face similar challenges as the Earth continues to warm, with melting polar ice leading to rising sea levels.

    "Over time, this may lead to the eventual loss of islands that these species currently rely upon to rest and raise their young."


    Bibliography:

    James P. Rule, David P. Hocking, Erich M. G. Fitzgerald.

    Pliocene monachine seal (Pinnipedia: Phocidae) from Australia constrains timing of pinniped turnover in the Southern Hemisphere.

    Journal of Vertebrate Paleontology, 2020; e1734015

    DOI: 10.1080/02724634.2019.1734015

    Tuesday, 24 March 2020

    Ancestor of all animals identified in Australian fossils


    A team led by UC Riverside geologists has discovered the first ancestor on the family tree that contains most familiar animals today, including humans.

    The tiny, wormlike creature, named Ikaria wariootia, is the earliest bilaterian, or organism with a front and back, two symmetrical sides, and openings at either end connected by a gut. The paper is published today in Proceedings of the National Academy of Sciences.

    The earliest multicellular organisms, such as sponges and algal mats, had variable shapes. Collectively known as the Ediacaran Biota, this group contains the oldest fossils of complex, multicellular organisms. However, most of these are not directly related to animals around today, including lily pad-shaped creatures known as Dickinsonia that lack basic features of most animals, such as a mouth or gut.

    The development of bilateral symmetry was a critical step in the evolution of animal life, giving organisms the ability to move purposefully and a common, yet successful way to organize their bodies. A multitude of animals, from worms to insects to dinosaurs to humans, are organized around this same basic bilaterian body plan.



    Evolutionary biologists studying the genetics of modern animals predicted the oldest ancestor of all bilaterians would have been simple and small, with rudimentary sensory organs. Preserving and identifying the fossilized remains of such an animal was thought to be difficult, if not impossible.

    For 15 years, scientists agreed that fossilized burrows found in 555 million-year-old Ediacaran Period deposits in Nilpena, South Australia, were made by bilaterians. But there was no sign of the creature that made the burrows, leaving scientists with nothing but speculation.

    Scott Evans, a recent doctoral graduate from UC Riverside; and Mary Droser, a professor of geology, noticed miniscule, oval impressions near some of these burrows. With funding from a NASA exobiology grant, they used a three-dimensional laser scanner that revealed the regular, consistent shape of a cylindrical body with a distinct head and tail and faintly grooved musculature. The animal ranged between 2-7 millimeters long and about 1-2.5 millimeters wide, with the largest the size and shape of a grain of rice -- just the right size to have made the burrows.

    "We thought these animals should have existed during this interval, but always understood they would be difficult to recognize," Evans said. "Once we had the 3D scans, we knew that we had made an important discovery."

    A 3D laser scan of an Ikaria wariootia impression. (Droser Lab/UCR)


    The researchers, who include Ian Hughes of UC San Diego and James Gehling of the South Australia Museum, describe Ikaria wariootia, named to acknowledge the original custodians of the land. The genus name comes from Ikara, which means "meeting place" in the Adnyamathanha language. It's the Adnyamathanha name for a grouping of mountains known in English as Wilpena Pound. The species name comes from Warioota Creek, which runs from the Flinders Ranges to Nilpena Station.

    "Burrows of Ikaria occur lower than anything else. It's the oldest fossil we get with this type of complexity," Droser said. "Dickinsonia and other big things were probably evolutionary dead ends. We knew that we also had lots of little things and thought these might have been the early bilaterians that we were looking for."

    In spite of its relatively simple shape, Ikaria was complex compared to other fossils from this period. It burrowed in thin layers of well-oxygenated sand on the ocean floor in search of organic matter, indicating rudimentary sensory abilities. The depth and curvature of Ikaria represent clearly distinct front and rear ends, supporting the directed movement found in the burrows.



    The burrows also preserve crosswise, "V"-shaped ridges, suggesting Ikaria moved by contracting muscles across its body like a worm, known as peristaltic locomotion. Evidence of sediment displacement in the burrows and signs the organism fed on buried organic matter reveal Ikaria probably had a mouth, anus, and gut.

    "This is what evolutionary biologists predicted," Droser said. "It's really exciting that what we have found lines up so neatly with their prediction."


    Bibliography:

    Scott D. Evans, Ian V. Hughes, James G. Gehling, and Mary L. Droser.

    Discovery of the oldest bilaterian from the Ediacaran of South Australia.

    PNAS, March 23, 2020

    DOI: 10.1073/pnas.2001045117

    Monday, 2 March 2020

    Discovery of a billion-year-old green algae, the ancestor of all plants


    Virginia Tech paleontologists have made a remarkable discovery in China: 1 billion-year-old micro-fossils of green seaweeds that could be related to the ancestor of the earliest land plants and trees that first developed 450 million years ago.

    The oldest green seaweed on record, the ancestor of all land plants, lived about 1 billion years ago, a new study finds.

    Scientists have discovered the fossils of what may be the oldest green algae ever known. The newfound seaweed — called Proterocladus antiquus — lived about a billion years ago. And even though it was tiny, about 0.07 inches (2 millimeters) in length, the algae had a big role: It could produce oxygen through photosynthesis.

    "Its discovery indicates that green plants we see today can be traced back to at least 1 billion years ago, and they started in the ocean before they expanded their territory to the land," study lead researcher Qing Tang, a postdoctoral fellow in the Department of Geosciences at Virginia Tech, have told Live Science in an email.



    Proterocladus antiquus : it confirms that green algae already lived a billion years ago

    Until now, researchers didn't have hard proof that green algae lived that long ago. Rather, computer models, including those based on molecular clocks, indicated that photosynthesizing plants arose between the Paleoproterozoic era (2.5 billion to 1.6 billion years ago) and the Cryogenian period (720 million to 635 million years ago).

    Now that researchers have a fossil, they can confidently say that photosynthesizing plants, a group known as Viridiplantae, lived at least 1 billion years ago, and that they were multicellular, Tang said.

    Fossil of green alga P. antiquus . Credits: Qing Tang et al. 2020


    "Previously, the oldest widely accepted fossilized green algae was about 800 million years old," said Timothy Gibson, a postdoctoral fellow in the Department of Earth Sciences at Dartmouth College in New Hampshire and the Department of Geology and Geophysics at Yale University, who was not involved with the study. "This work confirms what many have expected based on the existing, though sparse fossil record, which is that green algae likely existed about a billion years ago."

    Green algae: they played an important role in maintaining primitive ecosystems

    Tang and his colleagues discovered the fossils near Dalian City in Liaoning province of northern China. They had heard there was "a thick pile of well-exposed sedimentary rocks" from the Nanfen Formation dating to about a billion years ago. So, Tang took some of these ancient rocks, mostly mudstone and shale, back to the lab at Virginia Tech.

    Tang was "really excited" when he saw the algae fossil under the microscope. In all, he identified 1,028 specimens. "I showed it to my supervisor [Shuhai Xiao, a professor in the Department of Geosciences at Virginia Tech], and we immediately agreed that this was going to be a very interesting discovery," he said.

    Like modern algae, P. antiquus has a branched structure and a root system. Credits: Qing Tang et al. 2020

    Life on Earth is dependent on photosynthesizing plants and algae for food, yet land plants did not evolve until about 450 million years ago, Tang said. "The new fossil suggests that green seaweeds were important players in the ocean long before their descendants, land plants, took control," he said.

    Better understand the appearance and evolution of plants

    These fossils came from an ancient ocean, but there is still a debate about where green algae originated. "Not everyone agrees with us; some scientists think that green plants started in rivers and lakes, and then conquered the ocean and land later," Xiao said in a statement.



    Moreover, green algae isn't the oldest algae on record. "There is strong fossil evidence that red algae existed over a billion years ago, and we know the red and green algae diverged from a common ancestor," Gibson told Live Science in an email. "So, although this doesn't fundamentally change the way I'll think about the evolution of life, the discovery of this green algal fossil helps fill an important gap and strengthens an emerging timeline for the evolution of early, complex life."


    Bibliography:

    A one-billion-year-old multicellular chlorophyte

    Tang, Q., Pang, K., Yuan, X

    Nat Ecol Evol, 2020

    DOI: 10.1038/s41559-020-1122-9

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