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  • richardmitnick 1:42 pm on March 22, 2016 Permalink | Reply
    Tags: , , , Paleontology,   

    From UNSW: “A golden age of ancient DNA science begins” 

    U NSW bloc

    University of New South Wales

    22 Mar 2016
    Darren Curnoe

    1
    A reconstruction of a male our evolutionary cousin the Neanderthals (Modified from an image by Cicero Moraes). Wikimedia Commons, CC BY-SA

    OPINION: If I had taken a straw poll among anthropologists 10 years ago asking them how far genetic research would come in the next decade, I doubt anyone would have come close to predicting the big impact fossil DNA work would come to have.

    Back then, this nascent field was bogged down with fundamental issues like distinguishing authentic DNA from contamination. Simply recovering enough nuclear DNA to say anything sensible at all about human origins would have been a really big achievement.

    But following some remarkable technical developments in that time, including next generation sequencing, ancient DNA research is beginning to come of age.

    And it’s no exaggeration to say that it’s dramatically rewriting our understanding of the human evolutionary story and, unexpectedly, resolving some old, seemingly intractable, questions along the way.

    I say ‘beginning’ because despite the remarkable findings over the last half decade or so, many of which I have written about before, ancient DNA, particularly fossil genome research, has really only just begun.

    But, boy, what start!

    Two studies out last week in the journals Science and Nature are characteristic of the coming of age of ancient DNA studies; I’ll return to them shortly.

    As I see it – from the viewpoint of someone who studies the fossils – this field is beginning to provide answers to some big questions we’ve been wrestling with for a long, long, time.

    Here are three big issues which I think geneticists are making headway on, following decades of stalled progress by fossil specialists.

    1. There’s been a shift from merely documenting the occurrence of interbreeding between modern humans and archaic groups, like the Neanderthals and Denisovans, to a focus on the circumstances surrounding it and its consequences for living people.

    A few years back we fossil-jocks couldn’t agree about whether interbreeding had actually occurred or not. The case now seems to be closed thanks to the geneticists.

    Interbreeding occurred, but it wasn’t terribly common. Around 2 per cent of the genome of non-African people was inherited from Neanderthals, with slightly more DNA in Indigenous Oceanic Southeast Asians, New Guineans and Australians coming from the mysterious Denisovans (on top of their Neanderthal inheritance).

    Even among some living African populations, there is evidence for DNA inherited from an archaic species living on that continent perhaps as late as 30 thousand years ago.

    I suspect there will be more evidence found in the future, from other, perhaps as yet unknown, archaic species.

    One of the new studies – led by Benjamin Vernot from the University of Washington – examined 35 new genomes sequenced from people living in 11 locations in the Bismarck Archipelago of New Guinea to get a better handle on gene sharing with our archaic cousins.

    They confirmed evidence for ancient gene flow with the Neanderthals and have better characterised mating with the mysterious Denisovans, by comparing their new genomes with around 1,500 other human samples.

    The New Guinean samples showed between 1.9 and 3.4 per cent of their genomes to be derived from the Deniosvans.

    They also showed that a second ‘pulse’ of interbreeding is seen among living East Asians, Europeans and South Asians that wasn’t shared with New Guineans.

    There were seemingly three separate interbreeding events with the Neanderthals: one with the ancestors of New Guineans and Australians, one with early East Asians and one with the ancestors of South Asians and Europeans.

    Geneticists have now turned their attention to the specific genes that have been inherited by living humans from our archaic cousins and their consequences for understanding human adaptations and disease.

    I’ve looked at some of these previously, like those associated with the human immune system and high altitude adaptation.

    The really exciting area to be explored in the future is whether genes associated with features of the skeleton can be identified, helping us to make a direct connection with the physical changes documented in the fossil record and to understand how and why such changes came about.

    2. Ancient DNA is finally placing a framework around the vexed question, ‘how can we pick a new species from among the fossils’?

    For decades, anthropologists have been locking horns over how many species there might be in the human evolutionary tree; with estimates presently ranging from 5 to more than 25 species.

    So far, we’ve lacked an independent, objective, way to test our ideas. But, surprisingly, this is now emerging from comparisons of the human genome with those of our archaic cousins.

    For example, for over 100 years anthropologists have argued about whether the Neanderthals are a separate species to modern humans, or merely a sub-species of our kind.

    DNA has now given us an answer, and it should satisfy even the more hard nosed of anthropologists; although, experience tells me some of my colleagues will go the grave believing otherwise.

    Neanderthal, Denisovan and other archaic DNA is found unevenly throughout the human genome, occurring in hotspots, with vast deserts separating large stretches of archaic genes.

    One example is the human X-chromosome which is largely free of archaic DNA. This indicates that natural selection weeded out archaic genes, and also that male hybrid offspring of archaic and modern human matings were probably infertile.

    Anyone with a passing interest in the species questions will recognise immediately the importance of such a finding: humans and Neanderthals were different species, even if one applies the very strict criterion of ‘interbreeding’, so widely assumed to be indicative of species differences.

    Now, most anthropologists have considered the Neanderthals to be the closest extinct relative we humans have, regardless of their species status. Yet, DNA work shows they were highly biologically distinct from us, in accordance, as I see it, with their unusual physical features.

    To me, this indicates we should be prepared to recognise and accommodate many more species in the human tree, even after humans and Neanderthal had split.

    You might like to read my article about the complex question of species and their recognition in human evolution studies.

    3. Fossil DNA is now sorting out evolutionary relationships among human species.

    The second study from last week, led by Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology, recovered nuclear DNA from two specimens from the Spanish fossil site of Sima de Los Huesos (the ‘pit of bones’).

    These fossils are at least 430 thousand years old, and the new work builds on research by the team published last year where they were able to recover the much smaller and less informative mitochondrial genome from a fossil from the site.

    The mitochondrial DNA was found to be identical to the Deniosvans, but the new nuclear sequences are related to Neanderthals.

    So, the Sima de Los Huesos specimens are either very early Neanderthals or the ancestors of the Neanderthals; retaining the mitochondrial genome of their Denisovan ancestors, or perhaps even acquiring it through interbreeding.

    The work confirms nicely what some anthropologists have thought about the Sima de Los Huesos fossils from their anatomy.

    It also shows that the common ancestor of Neanderthals and modern humans lived more than 430 thousand years ago; in fact, the molecular clock in this new research indicates a split somewhere in the range of 550-765 thousand years ago.

    This means that the immediate ancestors of living humans evolved for at least 600 thousand years, probably longer, separately from the Neanderthals.

    I take away from this that it takes about 600 thousand years for hybrid sterility to kick in in humans. And, remembering that hybrid sterility is at the end of the process of species formation, we should expect there to be many more, short-lived, species in the human tree than we’ve recognised until now.

    Human evolution should be seen as a bush, with lot’s of twigs, rather than a thickly trunked tree, with only a small number of branches (species). I imagine diversity was the rule as we see in other living primates today.

    We modern humans were just one of many kinds of human, but oddly, the only one to persist today. Perhaps genomics might help us answer this mother of all mysteries in the not too distant future as well.

    See the full article here .

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  • richardmitnick 11:42 am on January 21, 2016 Permalink | Reply
    Tags: , , Paleontology, Sean_B._Carroll, The Day the Mesozoic Died   

    From Nautilus: “The Day the Mesozoic Died” 

    Nautilus

    Nautilus

    January 21, 2016
    Sean B. Carroll

    Temp 1

    “Understanding how we decipher a great historical event written in the book of rocks
    may be as interesting as the event itself.”
    —Walter Alvarez

    Built upon the slopes of Mount Ingino in Umbria, the ancient town of Gubbio boasts many well-preserved structures that document its glorious history. Founded by the Etruscans between the second and first centuries B.C., its Roman theater, Consuls Palace, and various churches and fountains are spectacular monuments to the Roman, Medieval, and Renaissance periods. It is one of those special destinations that draws tourists to this famous part of Italy.

    It was not the ancient architecture but the much longer natural history preserved in the rock formations outside the city walls that brought Walter Alvarez, a young American geologist, to Gubbio. Just outside the town lay a geologist’s dream—one of the most extensive, continuous limestone rock sequences anywhere on the planet (See Father and Son). The “Scaglia rossa” is the local name for the attractive pink outcrops found along the mountainsides and gorges of the area (“Scaglia” means scale or flake and refers to how the rock is easily chipped into the square blocks used for buildings, such as the Roman theater. “Rossa” refers to the pink color). The massive formation is composed of many layers that span about 400 meters in total. Once an ancient seabed, the rocks represent some 50 million years of Earth’s history.


    Watch and download mp4 video here .
    The Death of the Dinosaurs: The disappearance of the dinosaurs at the end of the Cretaceous period represented a long-standing scientific mystery. This three-act film tells the story of the extraordinary detective work that solved it. Howard Hughes Medical Institute

    Geologists have long used fossils to help identify parts of the rock record from around the world and Walter employed this strategy in studying the formations around Gubbio. Throughout the limestone he found fossilized shells of tiny creatures, called foraminifera or “forams” for short, a group of single-celled protists that can only be seen with a magnifying lens. But in one centimeter of clay that separated two limestone layers, he found no fossils at all. Furthermore, in the older layer below the clay, the forams were more diverse and much larger than in the younger layer above the clay (See Foraminifera). Everywhere he looked around Gubbio, he found that thin layer of clay and the same difference between the forams below and above it.

    Temp 2
    Father and Son: Luis (left) and Walter Alvarez at a limestone outcrop near Gubbio, Italy. Walter’s right hand is touching the top of the Cretaceous limestone, at the K-T boundary. Courtesy of Lawrence Berkeley National Laboratory

    Walter was puzzled. What had happened to cause such a change in the forams? How fast did it happen? How long a period of time did that thin layer without forams represent?

    These questions about seemingly mundane microscopic creatures and one centimeter of clay in a 1,300-foot-thick rock bed in Italy might appear to be trivial. But their pursuit led Walter to a truly Earth-shattering discovery about one of the most important days in the history of life.

    Temp 3
    Foraminifera : Walter Alvarez was puzzled by the rapid, dramatic change in foram size between the end of the Cretaceous (pictured at the bottom here) and the beginning of the Tertiary (top) periods, which is seen worldwide. These specimens are from a different location (not Gubbio). Images courtesy of Brian Huber, Smithsonian Museum of Natural History

    The K-T Boundary

    From the distribution of fossils and other geological data, it was known that the Gubbio formation spanned parts of both the Cretaceous [usually abbreviated K for its German translation Kreide (chalk)] and Tertiary periods. The names of these and other geological time periods come from early geologists’ ideas about the major intervals in Earth history, and from some of the features that mark particular times. In one scheme, the history of life is divided into three eras—the Paleozoic (“ancient life,” the first animals), the Mesozoic (“middle life,” the age of dinosaurs), and the Cenozoic (“recent life,” the age of mammals). The Cretaceous period, named after characteristic chalky deposits, forms the last third of the Mesozoic era. The Tertiary period (which has been renamed and subdivided into the Paleogene and Neogene) begins at the end of the Cretaceous 65 million years ago and ends at the beginning of the Quaternary period 2.6 million years ago.

    Temp 4
    Geologic time scale: Geologists organize Earth’s history into eras and periods. The KT boundary falls right at the border of the Cretaceous period and the Tertiary period, around 65 million years ago.

    Walter and his colleague Bill Lowrie spent several years studying the Gubbio formation, sampling up from the Tertiary and down through the Cretaceous. They were first interested in trying to correlate reversals in the Earth’s magnetic field with the fossil record as a way of deciphering the time-scale of Earth’s history. They learned to figure out where they were in the rock formation by the forams characteristic of certain deposits, and by learning to recognize the boundary between the Cretaceous and Tertiary rocks. That boundary was always right where the dramatic reduction in foram diversity size occurred. The rocks below were Cretaceous and the rocks above were Tertiary, and the thin layer of clay was in the gap between (See The K-T Boundary at Gubbio). The boundary is referred to as the K-T boundary.

    One thousand kilometers from Gubbio, at Caravaca on the southeast coast of Spain, a Dutch geologist, Jan Smit, had noticed a similar pattern of changes in forams in rocks around the K-T boundary. Smit knew that the K-T boundary marked the most famous extinction of all—the dinosaurs. When a colleague pointed out that fact to Walter, he became even more interested in those little forams and the K-T boundary.

    Temp 5
    The K-T boundary at Gubbio: The white Cretaceous limestone is separated from the reddish Tertiary limestone by a thin clay layer (marked with coin). Courtesy of Frank Schonian, Museum of Natural History, Berlin

    Walter was relatively new to academic geology. After he received his Ph.D. he had worked for the exploration arm of a multinational oil company in Libya, until Colonel Qaddafi expelled all of the Americans out of the country. His work on magnetic reversals had gone well but he realized that the abrupt change in the Gubbio forams and the K-T extinction presented a much bigger mystery that he became determined to solve.

    One of the first questions Walter wanted to answer, naturally, was how long it took for that thin clay layer to form? To answer this he would need some help. It is very common for children to get help from their parents with their science projects. However, it is extremely unusual, as it was in Walter’s case, that the “child” is in their late 30s. But few children of any age had a Dad like Walter’s.

    From A-Bombs to Cosmic Rays

    Luis Alvarez knew very little about geology or paleontology but he knew a lot about physics. He was a central figure in the birth and growth of nuclear physics. He received his Ph.D. in physics in 1936 from the University of Chicago and worked at the University of California, Berkeley under Ernest Lawrence, the recipient of the 1939 Nobel Prize in Physics for the invention of the cyclotron.

    His early work in physics was interrupted by the onset of World War II. During the first years of the war, Luis worked on the development of radar and systems that would help airplanes land safely in poor visibility. He received the Collier Trophy, the highest honor in aviation, for developing the Ground Controlled Approach (GCA) system for bad weather landings.

    In the middle of the war, he was recruited into the Manhattan Project, the top secret national effort to develop atomic weapons. Alvarez and his student Lawrence Johnston designed detonators for the bombs. Robert Oppenheimer, the director of the Manhattan Project, then put him in charge of measuring the energy released by the bombs. Luis was one of the very few to witness the first two atomic blasts. He flew as a scientific eyewitness to the first test of the atomic bomb in the New Mexico desert and then shortly thereafter to the bomb dropped on Hiroshima, Japan.

    After the war, Luis returned to physics research. He developed the use of large liquid hydrogen bubble chambers for tracking the behavior of particles. Luis received the Nobel Prize in Physics in 1968 for his work in particle physics.

    That would seem to be a nice capstone to an illustrious career. But several years later his son Walter moved to Berkeley, where Luis had worked for many years, to join the university’s geology department. This gave father and son the chance to talk often about science. One day, Walter gave his dad a small polished cross-section of Gubbio K-T boundary rock and explained the mystery within it. Luis, then in his late 60s, was hooked and started thinking about how to help Walter crack it. They started brainstorming about how to measure the rates of change around the K-T boundary. They needed some kind of atomic timekeeper.

    Luis, obviously an expert on radioactivity and decay, first suggested that they measure the abundance of beryllium-10 (10Be) in the K-T clay. This isotope is constantly created in the atmosphere by the action of cosmic rays on oxygen. The more time the clay represented, the more 10Be would be present. Luis put Walter in touch with a physicist who knew how to do the measurements. But just as Walter was set to work, he learned that the published half-life of 10Be was wrong, The actual half-life was shorter, and too little 10Be would be left after 65 million years to measure it.

    Fortunately, Luis had another idea.

    Space Dust

    Luis remembered that meteorites are 10,000 times richer in elements from the platinum group than is the Earth’s crust. He figured that the rain of dust from outer space should be falling, on average, at a constant rate. Therefore, by measuring the amount of space dust (platinum elements) in rock samples, one could calculate how long they had taken to form.

    These elements are not abundant, but they are measurable. Walter figured that if the clay bed had been deposited over a few thousand years, it would contain a detectable amount of platinum group material, but if it had been deposited more quickly, it would be free of these elements.

    Luis decided that iridium, not platinum itself, was the best element to measure because it was more easily detected. He also knew the physicists to do the measurements, the two nuclear chemists Frank Asaro and Helen Michel at the Berkeley Radiation Laboratory.

    Walter gave Asaro a set of samples from across the Gubbio K-T boundary. For months he heard nothing back. The analytical techniques Asaro was using were slow, his equipment was not working, and he had other projects to work on.

    Nine months later Walter got a call from his dad. Asaro wanted to show them his results. They had expected iridium levels on the order 0.1 parts per billion (ppb) of sample. Asaro found 3 ppb of iridium in the portion of the clay bed, about 30 times more than expected and than the level found in other layers of the rock bed.

    Temp 6
    The iridium anomaly: The levels of iridium across the Gubbio formation are plotted. Note the spike in the K-T boundary clay.Data redrawn from Alvarez, et al. 1980 by Leanne Olds

    Why would that thin layer have so much iridium?

    Before they got too carried away with speculation, it was important to know if the high level of iridium was an anomaly of rocks around Gubbio, or a more widespread phenomenon. Walter went looking for another exposed K-T boundary site that they could sample. He found a place called Stevns Klint, south of Copenhagen, Denmark. Walter visited the clay bed there and could see right away that “something unpleasant had happened to the Danish sea bottom” when the clay was deposited. The cliff face was almost entirely made of white chalk, full of all kinds of fossils. But the thin K-T clay bed was black, stunk of sulfur, and had only fish bones in it. Walter deduced that during the time this “fish clay” was deposited, the sea was an oxygen-starved graveyard. He collected samples and delivered them to Frank Asaro.

    In the Danish fish clay, iridium levels were 160 times background levels.

    Walter suggested to Jan Smit that he also look for iridium in his clay samples. The Spanish clay also contained a spike of iridium. So did a sample taken from a K-T boundary in New Zealand, confirming that the phenomenon was global.

    Something very unusual, and very bad, had happened at the K-T boundary. The forams, the clay, the iridium, the dinosaurs were all signs—but of what?

    It Came From Outer Space

    The Alvarez’s concluded right away that the iridium must have been of extraterrestrial origin. They thought of a supernova, the explosion of a star that could shower earth with its elemental guts. The idea had been kicked around before in paleontological and astrophysics circles.

    Luis knew that heavy elements are produced in stellar explosions, so if that idea was right, there would be other elements besides iridium in unusual amounts in the boundary clay. The key isotope to measure was plutonium-244 with a half-life of 75 million years. It would be still present in the clay layer, but decayed in ordinary earth rocks. Rigorous testing proved there was no elevated level of plutonium. Everyone was at first disappointed, but the sleuthing continued.

    Luis kept thinking of some kind of scenario that could account for a worldwide die-off. He thought that maybe the solar system passed through a gas cloud, that the sun had become a nova, or that the iridium could have come from Jupiter. None of these ideas held up. An astronomy colleague at Berkeley, Chris McKee, suggested that an asteroid could have hit the earth. Luis at first thought that would only create a tidal wave, and he could not see how a giant tidal wave could kill the dinosaurs in Montana or Mongolia.

    Then he started to think about the volcanic explosion of the island of Krakatoa, in 1883. He recalled that miles of rock had been blasted into the atmosphere and that fine dust particles had circled the globe, and stayed aloft for two years or more. Luis also knew from nuclear bomb tests that radioactive material mixed rapidly between hemispheres. Maybe a large amount of dust from a large impact could turn day into night for a few years, cooling the planet and shutting down photosynthesis?

    If so, how big an asteroid would it have been?

    From the iridium measurements in the clay, the concentration of iridium in so-called chondritic meteorites and the surface area of the Earth, Luis calculated the mass of the asteroid to be about 300 billion metric tons. He then used various methods to infer that the asteroid had a diameter of 10 ± 4 kilometers (km).

    That diameter might not seem enormous with respect to the 13,000-km diameter of the Earth. But now consider the energy of the impact. Such an asteroid would enter the atmosphere traveling at about 25 km per second—over 50,000 miles per hour. It would punch a hole in the atmosphere 10 km across and hit the planet with the energy of 108 megatons of TNT. (The largest atomic bomb ever exploded released the equivalent of about one megaton—the asteroid was 100 million times more powerful.) With that energy, the impact crater would be about 200 km across and 40 km deep, and immense amounts of material would be ejected from the impact.

    The team had their foram- and dinosaur-killing scenario.

    Hell on Earth

    The asteroid crossed the atmosphere in about one second, heating the air in front of it to several times the temperature of the sun. On impact, the asteroid vaporized, an enormous fireball erupted out into space, and rock particles were launched as far as halfway to the moon. Huge shock waves passed through the bedrock, then curved back up to the surface and shot melted blobs and bedrock out to the edge of the atmosphere and beyond. A second fireball erupted from the pressure on the shocked limestone bedrock. For a radius of a few hundred kilometers or more from ground zero, life was annihilated. Further away, matter ejected into space fell back to earth at high speeds—like trillions of meteors—heated up on re-entry, heating the air and igniting fires. Tsunamis, landslides, and earthquakes further ripped apart landscapes nearer to the impact.

    Elsewhere in the world, death came a bit more slowly.

    The debris and soot in the atmosphere blocked out the sun, and the darkness may have lasted for months. This shut down photosynthesis and halted food chains at their base. Analysis of plant fossils and pollen grains indicate that half or more plant species disappeared in some locations. Animals at successively higher levels of the food chain succumbed. The K-T boundary marks more than the end of the dinosaurs, it is also the end of belemnites, ammonites, and marine reptiles. Paleontologists estimate that more than half of all the planet’s species went extinct. On land, nothing larger than 25 kilograms in body size survived.

    It was the end of the Mesozoic world.

    Where Is the Hole?

    Luis, Walter, Frank Asaro, and Helen Michel put together the whole story—the Gubbio forams, the iridium anomaly, the asteroid theory, the killing scenario—in a single paper published in the journal Science in June 1980.1 It is a remarkable, bold synthesis across different scientific fields, perhaps unmatched in scope by any other single paper in the modern scientific literature. Jan Smit and Jan Hertogen published their study based on Spanish rocks in the journal Nature, and reached a similar conclusion.2

    They were concerned, however, that the scientific community was not well prepared to accept the impact hypothesis. They had good reason to be worried. For the previous 150 years, since the beginning of modern geology, the emphasis had been on the power of gradual change. The science of geology had supplanted biblical stories of catastrophes. The idea of a catastrophic event on Earth was not just disturbing, it was considered unscientific. Until the asteroid impact papers, explanations for the disappearance of the dinosaurs usually invoked gradual changes in climate or in the food chain to which the animals could not adapt.

    Some geologists scoffed at the catastrophe scenario and some paleontologists were not at all persuaded by the asteroid theory. It was pointed out that the highest dinosaur bone in the fossil record at the time was 3 meters below the K-T boundary. Some suggested that perhaps the dinosaurs were already gone when the asteroid hit.3 Other paleontologists rebutted that dinosaur bones are so scarce, one should not expect to find them right up against the boundary.4 Rather, they argued the rich fossil record of forams and other creatures is the more revealing record, and forams and ammonites do persist right up to the K-T boundary.

    Of course, there was a somewhat larger problem that begged explanation: Where on Earth was that huge crater? To the skeptics and proponents this was an obvious weakness of the hypothesis, and so the hunt was on to find the impact zone, if it existed.

    At the time, there were only three known craters on Earth 100 km or more in size. None were the right age. If the asteroid had hit the ocean, which, after all, covers more than two-thirds of the planet’s surface, then searchers might be out of luck. The deep ocean was not well mapped, and a substantial part of the pre-Tertiary ocean floor has been swallowed up into the deep Earth in the continual movement of tectonic plates.

    In the decade following the proposal of the asteroid theory, many clues and trails were pursued, often to dead ends. As the failures mounted, Walter began to believe that the impact had in fact been in an ocean.

    Then a promising clue emerged from a riverbed in Texas. The Brazos River empties into the Gulf of Mexico. The sandy bed of the river is right at the K-T boundary. When examined closely by geologists familiar with the pattern of deposits left by tsunamis, the sandy bed was found to have features that could only be accounted for by a giant tsunami, perhaps more than 100 meters high. Moroever, mixed in with the tsunami debris were tektites—small bits of glassy rock that were ejected from the impact crater in molten form and cooled as they rained back down to Earth.5,6

    Temp 7
    Tektites: Tektites from Dogie Creek, Wyoming (top) and Beloc, Haiti (bottom). Note the bubbles within the glassy sphere—these formed in the vacuum of space as the particles were ejected out of the atmosphere.Top figure courtesy of Geological Society of Canada; bottom figure from Smit, J. [5]

    Many scientists were on the hunt for the impact site. Alan Hildebrand, a graduate student at the University of Arizona was one of the most tenacious. Alan concluded that the Brazos River tsunami bed was a crucial hint to the crater’s location—that it was in the Gulf of Mexico or the Caribbean. He looked at available maps to see if there might be any candidate craters around. He found some rounded features on maps of the sea floor north of Colombia. He also learned of some circular-shaped “gravity anomalies,” places where the concentration of mass varies, on the coast of Mexico’s Yucatan Peninsula.

    Alan searched for any other hints that he was on the right track. Alan noticed a report of tektites in late Cretaceous rocks from a site on Haiti. When he visited the lab that had made the report, he recognized the material as impact tektites. He then went to Haiti and discovered that the deposits there included very large tektites, along with shocked quartz grains—another signature of impacts. He and his advisor William Boynton surmised that the impact site was within 1,000 km of Haiti.

    When Hildebrand and Boynton presented their findings at a conference, they were contacted by Carlos Byars, a reporter for the Houston Chronicle. Byars told Hildebrand that geologists working for the state-owned Mexican oil company PEMEX might have discovered the crater many years earlier. Glen Penfield and Antonio Camargo had studied the circular gravity anomalies in the Yucatan. PEMEX would not allow them to release company data but they did suggest at a conference in 1981—just a year after the Alvarez’s asteroid proposal—that the feature they mapped might be the crater. Penfield had even written to Walter Alvarez with that suggestion.

    In 1991, Hildebrand, Boynton, Penfield, Camargo, and colleagues formally proposed that the 180-km-diameter crater (almost exactly the size predicted by the Alvarez team) one-half mile below the village of Chicxulub [Cheech-zhoo-loob] on the Yucatan Peninsula was the long-sought K-T impact crater.7,8

    Temp 8
    Location of Chicxulub crater and key impact evidence sites: The map shows locations of various impact evidence—the tsunami bed in the Brazos River, tektites in Haiti, the Ocean Drilling Site 1049, and the crater and surrounding ejected material on the Yucatan Peninsula. Leanne Olds

    There were still crucial tests to be done to determine if Chicxulub was truly the “smoking gun.” Another important issue was the age of the rock. This was no easy task to determine because the crater was buried. The best approach would be to test the core rock samples from the wells drilled by PEMEX in the region decades earlier. At first, it was feared that all of the core samples had been destroyed in a warehouse fire. They were eventually located and the rock that was melted by the impact could be dated by a number of laboratories. The results were spectacular. One lab obtained a figure of 64.98 + 0.05 million years, another a value of 65.2 + 0.4 million years. Right on the button—the melt rock was the same age as the K-T boundary.

    The Haitian tektites were also dated to this age, as was a deposit of material ejected from the impact. Detailed chemical analysis showed that the Chicxulub melt rock contained high levels of iridium9 and that it and the Haitian tektites came from the same source. Furthermore, the Haitian tektites had extremely low water content and the gas pressure inside was nearly zero, indicating that the glass solidified while in ballistic flight outside the atmosphere.

    Within a little more than a decade, what had at first seemed to be a radical and, to some, outlandish idea, had been supported by all sorts of indirect evidence, and then ultimately confirmed by direct evidence. Geologists subsequently identified ejected material that covers most of the Yucatan and is deposited at more than 100 K-T boundary sites around the world.10 We now understand that the history of life on Earth has not been the steady, gradual process envisioned by generations of geologists since Lyell and Darwin.

    The identification of the huge crater, while a great advance for the asteroid theory, was bittersweet for Walter. Luis Alvarez had passed away in 1988, just before its discovery.

    Temp 9
    K-T boundary sites: At left, a core sample, drilled at a site about 500km east of Florida (Ocean Drilling Project Site 1049), beautifully depicts the K-T event. Note the very large layer of ejected material on top of which the iridium-containing layer settled. On the right, an exquisitely well-preserved site near Tbilisi, Republic of Georgia, reveals a graded layer of spherules (smaller particles at the top, larger at the bottom) ejected from the impact that is also highly enriched in iridium (86 ppb). Left image courtesy of Integrated Ocean Drilling Program; right image from Smit, J. [5]

    One Punch or Two?

    The discovery of the K-T asteroid impact prompted extensive examination of whether other extinctions were due to impacts. It appears that none of the other four major extinctions of the past 500 million years is attributable to an impact. Yet, there have been many sizable asteroid or comet impacts on Earth over the same period, although none as large as the K-T strike. Since most impacts do not cause extinctions, and most extinctions are not due to impacts, the question has been raised of why the K-T asteroid was so devastating?

    Some scientists have suggested that where the asteroid struck was important. The target rock that was vaporized included a large amount of gypsum, which liberated a large amount of sulfur aerosols that could exacerbate the blockage of the sun, as well as produce acid rain that would alter bodies of water as well as soils. In addition, the impact liberated a large amount of chlorine sufficient to destroy today’s ozone layer.11

    But other evidence has accumulated that a period of massive volcanic eruptions might have weakened Earth’s ecosystems before the K-T impact. The so-called Deccan Traps in present-day western India have been shown to have poured massive amounts of carbon dioxide and sulfur dioxide into the atmosphere in episodic eruptions beginning several hundred thousand years prior to the K-T impact.12 Indeed, for many years, there has been an ongoing debate among some scientists as to whether the Deccan Traps or the K-T impact were the primary cause of the mass extinction. Because of the temporal coincidence between the K-T impact and the onset of the mass extinction, the consensus view has been that the K-T impact was the primary cause of extinction.13 Very recently, new geological evidence has suggested a scenario that may reconcile both viewpoints. It now appears that the largest Deccan eruptions occurred very close to the time of the impact.14,15 This has led some scientists to suggest that the seismic effect of the impact rocking the Earth’s mantle may have been sufficient to trigger enormous, climate-altering eruptions. In this scenario, the asteroid would be the first punch, and volcanism the knockout blow.

    Sean B. Carroll is a professor of molecular biology and genetics at the University of Wisconsin-Madison and Vice President for Science Education at the Howard Hughes Medical institute. His new book The Serengeti Rules will be published in March by Princeton University Press.

    References

    1. Alvarez, L.W., Alvarez, W., Asaro, F., & Michel, H.V. Extraterrestrial cause for the Cretaceous-Tertiary extinction: Experimental results and theoretical interpretation. Science 208, 1095–1108 (1980).

    2. Smit, J. & Hertogen, J. An extraterrestrial event at the Cretaceous-Tertiary boundary. Nature 285, 198–200 (1980).

    3. Clemens, W.A., Archibald, J.D. & Hickey, L.J. Out with a whimper not a bang. Paleobiology 7, 293–98 (1981).

    4. Signor, P.W. & Lipps, J.H. Sampling bias, gradual extinction patterns and castastrophes in the fossil record. Geological Society of America Special Papers 190, 291–96 (1982).

    5. Smit, J. The global stratigraphy of the Cretaceous-Tertiary boundary impact ejecta. Annual Review of Earth and Planetary Sciences 27, 75–113 (1999).

    6. Simonson, B.M. & Glass, B.P. Spherule layers—Records of ancient impacts. Annual Review of Earth and Planetary Sciences 32, 329–361 (2004).

    7. Hildebrand, A.R., et al. Chicxulub crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico. Geology 19, 867–71 (1991).

    8. Pope, K.O., Ocampo, A.C., & Duller, C.E. Mexican site for K/T impact crater? Nature (Scientific Correspondence) 351, 105 (1991).

    9. Schuraytz, B.C., et al. Iridium metal in Chicxulub impact melt: Forensic chemistry on the K-T smoking gun. Science 271, 1573–1576 (1996).

    10. Claeys, P., Kiessling, W., & Alvarez, W. Distribution of Chicxulub ejecta at the Cretaceous-Tertiary Boundary. In Koeberl, C., & MacLeod, K.G., (Eds.) Catastrophic Events and Mass Extinctions: Impacts and Beyond Geological Society of America Special Paper, Boulder, CO (2002).

    11. Kring, D.A. The Chicxulub impact event and its environmental consequences at the Cretaceous-Tertiary boundary. Palaeogeography, Palaeoclimatology, Palaeoecology 255, 4-21 (2007).

    12. Schoene, B., et al. U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction. Science 347, 182-184 (2015).

    13. Schulte, P., et al. The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science 327, 1214–1218 (2010).

    14. Richards, M.A., et al. Triggering of the largest Deccan eruptions by the Chicxulub impact. Geological Society of America Bulletin (2015). Retrieved from doi: 10.1130/B31167.1

    15. Renne, P.R., et al. State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact. Science 350, 76-78 (2015).

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 11:01 am on January 18, 2016 Permalink | Reply
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    From The Guardian: “Titanosaurs: the largest animals ever to walk the Earth” 

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    The Guardian

    17 January 2016
    Ben Garrod

    How do you eat a skip full of food every day without ever chewing? How do you walk on tiptoes when you’re the length of four London buses? How do you have sex when you weigh 70 tons? While the answers to these three questions is probably “with great difficulty”, scientists are tackling such improbable questions after uncovering what is undoubtedly the biggest dinosaur excavation of all time.

    In the spring of 2014, a lone farmer scanned his land, looking for a lost sheep. He thought there was something odd about the rocky ledge his grizzled old sheep was perched on. Dinosaur finds aren’t uncommon in the area but the outcrop was huge – could it really be a bone? He called in the scientists. When they determined that the ledge was in fact the 8ft thigh bone of a dinosaur, this sleepy Argentinian farm became the most important dinosaur dig site for more than 100 years.

    Temp 1
    The Titanosaur replica at the American Museum of Natural History in New York. Photograph: Anadolu Agency/Getty Images

    Since its discovery, an international team of biologists, Hollywood model makers, a BBC film crew and palaeontologists, led by Dr Diego Pol and his colleagues from the Museum of Paleontology Egidio Feruglio in Argentina, has worked tirelessly and after 40,000 hours’ work, the results are astounding. The team discovered that not only was this giant herbivore a new species but it was the largest dinosaur ever, dwarfing its closest competitors. What’s more, the team found that seven of these animals actually died in the exact same spot, across at least three different occasions, approximately 101.6 million years ago.

    This new dinosaur belongs to a group known as the sauropods, the long-necked, big-bodied beasts usually found roaming around in herds in the background of Hollywood dinosaur blockbusters. If you’ve seen Dippy at the Natural History Museum in London, then you’ll know what a sauropod is. Within this fascinating group of large herbivorous dinosaurs, however, a subsection is known as the titanosaurs and, as the name suggests, these are the real giants – the ones that literally shook the ground. They followed on from the extinction of smaller sauropods, such as the better-known diplodocids and brachiosauridae, and were found across the world. South America is especially rich in titanosaur fossils and already, true giants such as Puertasaurus and Argentinosaurus have been unearthed there.

    Temp 2
    David Attenborough with a giant titanosaur’s 8ft-long thigh bone. Photograph: Robin Cox/BBC

    Describing any new species can be a delicate subject, so introducing the largest dinosaur to both the scientific community and the wider world will be a huge task. Everyone wants their giant dinosaur to hold the title of “biggest” and, with multiple methods for assessing size to choose from, the team needed to be certain of what they’d found. Body size estimations can vary according to the technique used and on how much of the skeleton is retrieved. Estimates for the previous biggest dinosaur, Argentinosaurus, are based on fewer than 20 bones and Puertasaurus size estimates on just four vertebrae.

    The difference with this newly discovered titanosaur is that much of the skeleton has been found. From the seven individuals, 223 bones have been recovered to date, allowing Pol and his team to use multiple methods to develop a reliable size estimate. Their results show that this dinosaur was 37m in length and weighed 70 metric tons, making it the largest animal ever to walk the face of the planet.

    These dinosaurs had to sustain this incredible weight on four specially adapted column-like legs. They were so big they probably used the heavy musculature running from their thighs to halfway down their tails to gain momentum for walking. What’s more, in order to survive the stresses and fractures that could easily result from such extreme weights, these animals not only evolved to reduce the toes in their forelimbs, forcing them to walk on horseshoe-shaped stumps of reduced metacarpal bones, they walked on tiptoes, with huge fleshy pads cushioning the impact as they moved.

    Weighing as much as up to 15 African elephants, this new species of dinosaur hasn’t even been named yet and although we still can’t fully explain why seven animals were found together, the 80 or so giant serrated carnivore teeth from an unknown killer found alongside the bones hint at a murderous end for these gentle giants. However, as a lifesize replica skeleton is unveiled at New York’s American Museum of Natural History, this super-size discovery is set not only to inspire a new generation of dinosaur fans but will stoke the fires of scientific debate for years to come.

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  • richardmitnick 8:05 am on May 22, 2015 Permalink | Reply
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    From NBC via U Washington: “T. Rex’s Cousin? Scientists Find Washington State’s First Dinosaur Fossil” 

    NBC News

    NBC News

    U Washington

    May 20 2015
    Laura Geggel, Live Science

    1
    The University of Washington’s Brandon Peecook holds up a cast of a Daspletosaurus femur at right, while Christian Sidor holds the newly described fossil fragment at right for a size comparison.Burke Museum / UW

    A fragmented femur bone hidden underwater for millions of years has provided the first evidence that a dinosaur once roamed Washington state.

    And not just any dinosaur: Researchers say this beast was a theropod — a two-legged, mostly meat-eating group of beasts that are linked to modern-day birds. Other theropods include Tyrannosaurus rex and Velociraptor.

    Scientists found the 80 million-year-old fossil of the dinosaur when they were searching for ammonites — extinct marine invertebrates with spiral shells — and other fossilized animals. They had focused their fieldwork in the San Juan Islands, an archipelago located a short ferry ride away from Seattle.

    In April 2012, when the tide was out, they noticed a fossilized bone embedded in the marine rock. The researchers immediately contacted paleontologists at the University of Washington, who sent out a team in May of that year to excavate the fossil with a rock saw.

    “The rock there is tremendously hard, so it took them a full day to excavate it,” said Christian Sidor, a co-author of the study and a curator of vertebrate paleontology at the Burke Museum at the University of Washington.

    Sidor and his colleagues spent about a year and a half preparing the fossil, and “for the longest time, I was unconvinced that we were going to be able to say anything else besides ‘It’s a large bone,'” he told LiveScience. “What was exposed on the surface really had no anatomy. I couldn’t tell if it was a dinosaur, couldn’t tell if it was a marine reptile, couldn’t tell anything about it.”

    Once they removed the fossil from the rock and flipped it over, the researchers saw several signs that the fossil was half of the left femur (thighbone) of a theropod dinosaur. It measures 16.7 inches long by 8.7 inches wide (42 by 22 centimeters) but would have been almost 4 feet (1.2 meters) long — or slightly smaller than a T. rex thighbone — before it broke, the researchers said.

    Several clues suggest the fossil belonged to a theropod, Sidor said. For instance, the fossil once had a hollow middle cavity, which was unique to theropods during the late Cretaceous period. The bone also had a feature positioned closely to the hip, called a fourth trochanter. That feature is commonly associated with theropods. The researchers said it “seems likely” that the creature was a tyrannosauroid, a older cousin of T. rex.

    The specimen was uncovered near fossils of the clam species Crassatellites conradiana, which lived in shallow water. This suggests that the dinosaur died near the sea, was tossed around by the waves and found its resting place among the clams, the researchers said.

    The find makes Washington the 37th U.S. state known to have dinosaur fossils.

    Active plate tectonics and a vast amount of urban development have made it difficult for scientists to find dinosaur fossils in Washington, the researchers said. However, isolated dinosaur skeletons and bones have been found in nearby regions such as Oregon, California and south central Alaska.

    The study was published online Wednesday in the journal PLOS ONE. The fossil is due to go on display at the Burke Museum on May 21.

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  • richardmitnick 5:02 am on March 5, 2015 Permalink | Reply
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    From NYT: “Jawbone’s Discovery Fills Barren Evolutionary Period” 

    New York Times

    The New York Times

    MARCH 4, 2015
    JOHN NOBLE WILFORD

    1
    The Ledi-Geraru mandible fossil. Credit William Kimble/Arizona State University

    On the morning of Jan. 29, 2013, Chalachew Seyoum was climbing a remote hill in the Afar region of his native Ethiopia, his head bent, eyes focused on the loose sediment. The site, known as Ledi-Geraru, was rich in fossils. Soon enough, he spotted a telltale shape on the surface — a premolar, as it turned out. It was attached to a piece of a mandible, or lower jawbone. He collected other pieces of a left mandible, and five teeth in all.

    Mr. Seyoum, a graduate student in paleoanthropology at Arizona State University, had made a discovery that vaulted evolutionary science over a barren stretch of fossil record between two million and three million years ago. This was a time when the human genus, Homo, was getting underway. The 2.8-million-year-old jawbone of a Homo habilis predates by at least 400,000 years any previously known Homo fossils.

    More significant, scientists say, is that this H. habilis lived only 200,000 years after the last known evidence of its more apelike predecessors, Australopithecus afarensis, the species made famous by “Lucy,” whose skeleton was found in the 1970s at the nearby Ethiopian site of Hadar.

    2
    The fossil of Olduvai Hominid 7, includes a partial lower jaw, bones of the brain case and hand bones. Credit John Reader

    William H. Kimbel, director of the Institute of Human Origins at Arizona State, said the Ledi-Geraru jaw “helps narrow the evolutionary gap between Australopithecus and early Homo,” adding that it was an excellent “transitional fossil in a critical time period in human evolution.”

    The discovery was announced Wednesday in two reports for the journal Science by researchers at Arizona State, the University of Nevada, Las Vegas, and Pennsylvania State University. One paleoanthropologist not on the teams, Fred Spoor of University College London and the Max Planck Institute for Evolutionary Anthropology in Germany, endorsed the analysis.

    3
    The Ledi-Geraru mandible fossil. Credit William Kimble/Arizona State University

    Dr. Spoor said in an email that he agreed with the hypothesis that the new Ledi-Geraru mandible “derives from Australopithecus afarensis, and at 2.8 million years shows morphology that is ancestral to all early Homo.”

    How could Dr. Spoor not agree with the interpretation of the findings in the new report by Brian A. Villmoare of the University of Nevada, Las Vegas, and colleagues on the Arizona State team? By coincidence, Dr. Spoor was ready to predict many of the findings in the journal Nature a day before his predictions would have been proved right in the journal Science. When the relationship between the studies became clear, the two journals agreed to simultaneous publication of the articles on Wednesday.

    4
    The hills of the Lee Adoyta region in Ethiopia expose sediments that are less than 2.67 million years old, which helps to date the mandible. Credit Erin DiMaggio/Penn State University

    Dr. Spoor’s predictions were drawn from a digital reconstruction of the disturbed remains of the jaws of the original 1.8-million-year-old Homo habilis specimen found 50 years ago by the legendary fossil hunters Louis and Mary Leakey at Olduvai Gorge in Tanzania.

    The reconstruction, suggesting a plausible evolutionary link between A. afarensis and H. habilis, yielded a remarkably primitive picture of a deep-rooted diversity of a species that emerged much earlier than the 2.3 million years ago suggested by some specimens. The teeth and jaws appeared to be more similar to A. afarensis than to subsequent Homo erectus or Homo sapiens, modern humans that emerged about 200,000 years ago.

    Dr. Spoor’s analysis also seemed to put a new face on H. habilis. He said that individual species of early Homo were more easily recognizable by jaw structure and facial features than by differences in brain size, which tend to be highly variable. Dr. Villmoare and colleagues made similar observations in their article. Both the predictions and the mandible findings called attention to smaller teeth with the emergence of H. habilis and evidence suggesting that the species probably split in different evolutionary lines, only one of which might have been ancestral to later H. erectus and H. sapiens.

    In an email, Dr. Spoor explained that the split occurred sometime before 2.3 million years ago. The lineage leading to H. habilis must have kept the primitive jaw morphology. The Ledi-Geraru specimen kept the primitive, sloping chin that links it to a Lucy-like ancestor. Other lineages must account for the fact that H. erectus and H. habilis existed together for a period more than a million years ago.

    In a second report for the journal Science, Erin N. DiMaggio of Penn State and other geologists examined soil, vegetation and fossils at Ledi-Geraru. They determined that when the H. habilis left its jaw there, the habitat was dominated by mammals that lived in a more open landscape — grasslands and low shrubs — than the more wooded land often favored by A. afarensis.

    But after about 2.8 million years ago, increased African aridity has been cited as a possible result of widespread climate change affecting species changes and extinctions. Kaye E. Reed, co-leader of the Arizona State team, noted that the “aridity signal” had been observed at the Ethiopian fossil site. However, she said, “it’s still too soon to say this means climate change is responsible for the origin of Homo.”

    For that, Dr. Reed said, “we need a larger sample of hominin fossils, and that’s why we continued to come to the Ledi-Geraru area to search.” That, and to learn more about the evolution of our genus, Homo.

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  • richardmitnick 4:11 am on February 26, 2015 Permalink | Reply
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    From livescience: ” Earth’s Worst Mass Extinction Preserved Ancient Footprints” 

    Livescience

    February 25, 2015
    Shannon Hall

    1
    Graduate student Tracy Thomson stands next to a site called Chimney Rock in Capitol Reef National Park. It shows the track of a swimming animal drifting diagonally in a current.
    Credit: Tracy Thomson

    Earth’s worst mass extinction may have created ideal conditions for preserving the ancient footprints of giant reptiles on the muddy ocean floor, according to a new study.

    Researchers found a spike in fossilized tracks of tetrapods (these early four-limbed vertebrates include amphibians, reptiles, birds and mammals) during the early Triassic period, roughly 250 million years ago. This increase may be the result of a mass extinction at the end of the Permian period that wiped out worms and other tiny creatures that typically churn up ocean sediments, leaving behind sticky seafloor conditions that preserved the wading and swimming habits of ancient giant reptiles, the scientists said.

    The researchers captured a “Goldilocks” window when they could see this behavior simply because they had “this magical time after this mass extinction,” said study co-author Mary Droser, a professor of geology at the University of California, Riverside.

    The start of the Triassic period was a desolate time in Earth’s history. Something — a bout of volcanic eruptions, climate change or even an asteroid impact — triggered the extinction of more than 90 percent of Earth’s marine species. However, it allowed giant reptiles, such as the dolphin-shaped ichthyosaurs and the long-necked plesiosaurs, to flourish well before the evolution of dinosaurs.

    Most of these reptiles preyed on fish and ancient squid. When they walked through the water, their claws pushed against the seafloor, and their bodies trailed through the muddy bottom, leaving noticeable swim tracks. But preserving such tracks for hundreds of millions of years isn’t easy, since footprints in sand typically dissolve quickly.

    Scientists were surprised to find a large number of fossilized swim tracks from the early Triassic. They found only a few well-preserved swim tracks from other epochs, like the Permian (before the Triassic) and the Jurassic (after the Triassic), but the team counted roughly 40 from the early Triassic. Although it’s easy to assume that this is because there were more reptiles living in the early Triassic than during the other periods, the researchers speculated that the mass extinction at the end of the Permian period actually created conditions ripe for preserving fossil tracks.

    After the extinction, most animals living in the soil had died, so they couldn’t mix the soil up quite as much. Typically, “there are all sorts of things that keep that sediment mixed,” Droser said. “But if you take them away, then the mud becomes sticky and hard.” This means that a footprint, or the slithering track of a belly against the ocean floor, for example, won’t disappear as quickly.

    Tracy Thomson, a University of California, Riverside graduate student working with Droser, spent two summers in Utah uncovering the rare swim tracks. Now a barren desert, the coastline used to run through Glen Canyon and Capitol Reef National Park. It was there that the reptiles would stray by the bays and lagoons before wading a foot or two (0.3 to 0.6 meters) in the water to hunt.

    Before now, no one had noticed this spike, for a number of reasons, Droser said. For one, swim tracks are relatively new, scientifically speaking: It was only recently that researchers discovered that these fossils are made by reptiles underwater, and the key is that these tracks tend to meander, and even disappear, for short distances before reappearing, Droser explained.

    The reptiles “are meaning to stay on the substrate, to stay on the ground,” Droser said. But the water’s current lifts them up, and “they get carried a little bit until they find their footing again,” she said. As such, the tracks rarely move in a straight line, Droser added.

    By providing a window into this unique time, Droser and Thomson hope to shed light on Earth’s largest mass extinction, which is sometimes called the Great Dying.

    The study was published online Feb. 5 in the journal Geology.

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  • richardmitnick 5:11 am on February 24, 2015 Permalink | Reply
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    From The Siberian Times: “Is this 415 million-year-old fish our earliest known human ancestor?” 

    Siberian Times

    The Siberian Times

    18 February 2015
    Derek Lambie

    Tests on tiny scull found in Siberia give breakthrough on evolution and could hint at the ‘missing link’ to mankind’s origins.

    1
    ‘It’s a very interesting fossil, and it’s very small. It’s surprising that something so tiny could have so much information in it.’ Picture: Samantha Giles

    A tiny 415 million-year-old fish skull found in Siberia could provide the so-called ‘missing link’ to the origins of human kind, scientists have claimed. With many common characteristics to animals that live in the sea, many palaeontologists believe we began life in the water and evolved from fish. Now the miniscule remains, just two centimetres in width and still embedded in rock, have added weight to that theory and could give clues about what our earliest ancestor looked like. Originally uncovered in the 1970s on Putorana Plateau, the fossil was recently re-examined in the United Kingdom using state-of-the-art 3D scanning equipment. There are two main types of living jawed vertebrates: those made of bone and those made of cartilage. But what scientists found was that the ancient fish’s brain case had the characteristics of both modern-day bony fish, such as salmon and trout, and fish made of cartilage, including sharks and manta rays. It means the fossil is likely to be one of the common ancestors of the two groups, which split apart 420 million years ago, and could offer hints about the origins of all jawed vertebrates, including reptiles and humans. The findings, published in the international scientific journal Nature, have been heralded by some palaeontologists as being ‘truly remarkable’.

    2
    Janusiscus schultzei is likely to be one of the common ancestors of the two groups, which split apart 420 million years ago, and could offer hints about the origins of all jawed vertebrates, including reptiles and humans. Picture: Samantha Giles

    Samantha Giles, the lead researcher and a paleobiology doctoral candidate at Oxford University, said: ‘It’s a very interesting fossil, and it’s very small. It’s surprising that something so tiny could have so much information in it. ‘There are over 60,000 species of living jawed vertebrates, and they encompass pretty much everything you can think of [with a backbone] that lives on land or in the sea. But we don’t really know what they looked like when they split.’ When the small fossil was first discovered, scientists classified the specimen as a bony fish and no further examination of it was done until recently. Ms Giles and her research team used a CT scanner to look at the skull and create a three-dimensional model by taking hundreds of images from different angles. The detailed scans showed that the fish had sensory line canals on its skull, like those used by bony fish on the outside of their bodies to sense changes in the pressure around them and avoid predators. But, crucially, it also shared characteristics with cartilaginous fish, with blood vessels inside the skull, above and between the jaws, to supply oxygen to its brain. The fossil was named Janusiscus schultzei in honour Janus the Roman god of transitions who is often shown with two faces, and Hans-Peter Schultze, from the University of Kansas and who first described it in 1977.

    2
    Putorana Plateau, where the fossil was found in 1972. Picture: Cont

    Many believe humans evolved from some form of fish life, with a number of our current anatomical characteristics — including the way embryos are formed, the existence of the philtrum groove below our noses and the way in which people hiccup – thought to stem from our time in the water. John Long, a professor of palaeontology at Flinders University in Adelaide, described the findings at Oxford as ‘truly remarkable’. He told the Live Science website: ‘I think it is a highly significant discovery, as the origin and diversification of modern bony-jawed fishes is still shrouded in mystery. But Janusiscus takes us a big step closer to really understanding this major evolutionary transition, from primitive jawed fishes to the beginning of the modern jawed fish fauna.’ Sadly scientists were unable to find out more about the jawed fish because its jaw was actually missing from the fossil. Ms Giles said: ‘Presumably, the jaw is in a middle of the river somewhere in Siberia.’

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  • richardmitnick 9:13 am on February 3, 2015 Permalink | Reply
    Tags: , Microorganisms, , Paleontology,   

    From UCLA: “Scientists discover organism that hasn’t evolved in more than 2 billion years” 

    UCLA bloc

    UCLA

    February 02, 2015
    Stuart Wolpert

    1
    A section of 1.8 billion-year-old fossil-bearing rock. The fossils (dark areas) are essentially identical to fossils 500 million years older and to modern microorganisms.
    UCLA Center for the Study of Evolution and the Origin of Life

    Research actually provides further support for Darwin, UCLA professor says

    An international team of scientists has discovered the greatest absence of evolution ever reported — a type of deep-sea microorganism that appears not to have evolved over more than 2 billion years. But the researchers say that the organisms’ lack of evolution actually supports Charles Darwin’s theory of evolution.

    The findings are published online today by the Proceedings of the National Academy of Sciences.

    The scientists examined sulfur bacteria, microorganisms that are too small to see with the unaided eye, that are 1.8 billion years old and were preserved in rocks from Western Australia’s coastal waters. Using cutting-edge technology, they found that the bacteria look the same as bacteria of the same region from 2.3 billion years ago — and that both sets of ancient bacteria are indistinguishable from modern sulfur bacteria found in mud off of the coast of Chile.

    “It seems astounding that life has not evolved for more than 2 billion years — nearly half the history of the Earth,” said J. William Schopf, a UCLA professor of earth, planetary and space sciences in the UCLA College who was the study’s lead author. “Given that evolution is a fact, this lack of evolution needs to be explained.”

    3
    Deep-sea microorganisms are unchanged over more than 2 billion years (UCLA Center for the Study of Evolution and the Origin of Life)

    Charles Darwin’s writings on evolution focused much more on species that had changed over time than on those that hadn’t. So how do scientists explain a species living for so long without evolving?

    2
    UCLA professor J. William Schopf pioneered the techniques used to analyze microscopic fossils preserved inside ancient rocks.(John Vande Wege/UCLA)

    “The rule of biology is not to evolve unless the physical or biological environment changes, which is consistent with Darwin,” said Schopf, who also is director of UCLA’s Center for the Study of Evolution and the Origin of Life. The environment in which these microorganisms live has remained essentially unchanged for 3 billion years, he said.

    “These microorganisms are well-adapted to their simple, very stable physical and biological environment,” he said. “If they were in an environment that did not change but they nevertheless evolved, that would have shown that our understanding of Darwinian evolution was seriously flawed.”

    Schopf said the findings therefore provide further scientific proof for Darwin’s work. “It fits perfectly with his ideas,” he said.

    The fossils Schopf analyzed date back to a substantial rise in Earth’s oxygen levels known as the Great Oxidation Event, which scientists believe occurred between 2.2 billion and 2.4 billion years ago. The event also produced a dramatic increase in sulfate and nitrate — the only nutrients the microorganisms would have needed to survive in their seawater mud environment — which the scientists say enabled the bacteria to thrive and multiply.

    Schopf used several techniques to analyze the fossils, including Raman spectroscopy — which enables scientists to look inside rocks to determine their composition and chemistry — and confocal laser scanning microscopy — which renders fossils in 3-D. He pioneered the use of both techniques for analyzing microscopic fossils preserved inside ancient rocks.

    Co-authors of the PNAS research were Anatoliy Kudryavtsev, a senior scientist at UCLA’s Center for the Study of Evolution and the Origin of Life, and scientists from the University of Wisconsin, NASA’s Jet Propulsion Laboratory, Australia’s University of New South Wales and Chile’s Universidad de Concepción.

    Schopf’s research is funded by the NASA Astrobiology Institute.

    See the full article here.

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    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 4:45 am on January 29, 2015 Permalink | Reply
    Tags: , , Paleontology   

    From NYT: “Skull Fossil Offers New Clues on Human Journey From Africa” 

    New York Times

    The New York Times

    JAN. 28, 2015
    JOHN NOBLE WILFORD

    1
    Anthropologists discovered a 55,000-year-old skull fossil in the Manot Cave in western Galilee in 2008, and it was subjected to years of analysis. Credit Menahem Kahana/Agence France-PresseGetty Images

    Anthropologists exploring a cave in Israel have uncovered a rare 55,000-year-old skull fossil that they say has a story to tell of a reverberating transition in human evolution, at a point when and where some early humans were moving out of Africa and apparently interbreeding with Neanderthals.

    The story is of when the Levant was a corridor for anatomically modern humans who were expanding out of Africa and then across Eurasia, replacing all other forms of early human-related species. Given the scarcity of human fossils from that time, scholars say, these ancestors of present-day non-African populations had remained largely enigmatic.

    From the new fossil find, which could be closely related to the first modern humans to colonize Stone Age Europe, it appears that these people already had physical traits a bit different from the Africans they were leaving behind and many other human inhabitants along the corridor.

    Could this support recent genetic evidence that modern Homo sapiens and their Neanderthal cousins interbred, perhaps in the Middle East and most likely between 65,000 and 47,000 years ago? The discovery team urged caution on the interbreeding issue, but noted anatomical features of the cranium suggesting that some human-Neanderthal mixture had presumably occurred before any encounters in Europe and Asia.

    2
    Researchers working in the Manot Cave in western Galilee. Credit Israel Hershkovitz, Ofer Marder & Omry Barzilai, via Reuters

    The discovery in Manot Cave in western Galilee, made in 2008 and subjected to years of rigorous analysis, was reported on Wednesday in the journal Nature by an international team of researchers led by Israel Hershkovitz of Tel Aviv University. They said this was “the first fossil evidence from the critical period when genetic and archaeological models predict that African modern humans successfully migrated out of Africa and colonized Eurasia.”

    The researchers further concluded that the Manot specimen “provides important clues about the morphology of modern humans in close chronological proximity to a probable interbreeding event with Neanderthals.” They also noted that the shape of the cranium established this as a fully modern human at a time when warmer and wetter conditions were favorable for human migration out of Africa.

    In other words, Dr. Hershkovitz said in an interview, the Manot cranium “is the missing connection between African and European populations.”

    Scientists not involved with the research team praised the “fascinating new fossil” and the cautious interpretation of its broader implications in understanding the early migrations into Eurasia. “This fossil fits previous predictions,” said Eric Delson, a paleoanthropologist at Lehman College of the City University of New York, “which is a nice rarity in our field.”

    Dr. Delson, also a researcher at the American Museum of Natural History, added, “As always, we want more fossils to document variations in and details about this presumed fossil population.”

    3
    From left, a Neanderthal skull, the Manot cranium and a complete modern human skull on display near the cave in Israel where the Manot cranium was found. Credit Jim Hollander/European Pressphoto Agency

    In an email, Dr. Delson praised the journal authors “for hitting the mark with their analyses and interpretations, reaching all the possible conclusions one could think of: The partial skull combines a basically modern human form with a few features also found in Neanderthals.” In addition, he pointed out, the analysis “supports the similarity of its shapes” to those of modern Africans and early modern humans from Europe, such as the Cro-Magnons.

    The partial skull, designated Manot 1, is of a fairly small adult individual, its sex undetermined. The distinctive bunlike shape at the base of the skull resembles modern African and European skulls but differs from other anatomically modern humans from the Levant, and is thus a strong clue that these were among the first humans to settle Europe, scientists said.

    Dr. Delson agreed that the evidence “makes it possible that this individual is (or is descended from) a ‘hybrid’ between modern humans and Neanderthals, but as the authors note, such a conclusion cannot be reached from a single fossil, especially as hybrids between species of modern primates usually have some genetically related anatomical oddities.”

    One concern is that the fossil skull is fairly small, with a somewhat lower braincase capacity than in modern humans. With only one specimen, it is hard to know whether this is normal for the general population, scientists said. And Dr. Delson said it would be interesting to test for DNA in the skull to support its possible hybrid status in a time of overlapping modern human-Neanderthal populations when early humans were making their way, as he phrased it, to “that small zoological backwater of Eurasia known as Europe.”

    Excavations at Manot Cave are expected to continue through at least 2020, searching deeper for more fossils and artifacts from the migrating people. Israel, Dr. Hershkovitz said, “is like a Swiss cheese, lots of caves everywhere.”

    Several caves in the vicinity of Manot were occupied for long times by Neanderthals between 65,000 and 50,000 years ago. In this respect, Dr. Hershkovitz said, Manot is an excellent place to search for possible hybrids, but they may be difficult to recognize from surface features. “Only DNA study will solve the problem,” he said.

    See the full article here.

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  • richardmitnick 4:23 am on January 29, 2015 Permalink | Reply
    Tags: , , , Paleontology,   

    From U Alberta: “Long-necked ‘dragon’ discovered in China “ 

    U Alberta bloc

    University of Alberta

    January 28, 2015
    Kristy Condon

    2
    Artist’s conception of Qijianglong, chased by two carnivorous dinosaurs in southern China 160 million years ago (Illustration: Lida Xing)

    University of Alberta paleontologists including PhD student Tetsuto Miyashita, former master’s student Lida Xing and professor Philip Currie have discovered a new species of a long-necked dinosaur from a skeleton found in China. The findings have been published in a new paper in the Journal of Vertebrate Paleontology.

    Qijianglong (pronounced “CHI-jyang-lon”) is about 15 metres long and lived about 160 million years ago in the Late Jurassic. The name means “dragon of Qijiang,” for its discovery near Qijiang City, close to Chongqing. The fossil site was found by construction workers in 2006, and the digging eventually hit a series of large neck vertebrae stretched out in the ground. Incredibly, the head of the dinosaur was still attached.

    “It is rare to find a head and neck of a long-necked dinosaur together because the head is so small and easily detached after the animal dies,” explains Miyashita.

    The new species belongs to a group of dinosaurs called mamenchisaurids, known for their extremely long necks sometimes measuring up to half the length of their bodies. Most sauropods, or long-necked dinosaurs, have necks only about one-third the length of their bodies.

    Unique among mamenchisaurids, Qijianglong had neck vertebrae that were filled with air, making their necks relatively lightweight despite their enormous size. Interlocking joints between the vertebrae also indicate a surprisingly stiff neck that was much more mobile bending vertically than sideways, similar to a construction crane.
    Dino101

    “Qijianglong is a cool animal. If you imagine a big animal that is half neck, you can see that evolution can do quite extraordinary things,” says Miyashita.

    Mamenchisaurids are only found in Asia, but the discovery of Qijianglong reveals that there could be as many differences among mamenchisaurids as there are between long-necked dinosaurs from different continents.

    “Qijianglong shows that long-necked dinosaurs diversified in unique ways in Asia during Jurassic times—something very special was going on in that continent,” says Miyashita. “Nowhere else we can find dinosaurs with longer necks than those in China. The new dinosaur tells us that these extreme species thrived in isolation from the rest of the world.”

    Miyashita believes that mamenchisaurids evolved into many different forms when other long-necked dinosaurs went extinct in Asia. “It is still a mystery why mamenchisaurids did not migrate to other continents,” he says. It is possible that the dinosaurs were once isolated as a result of a large barrier such as a sea, and lost in competition with invading species when the land connection was later restored.

    The Qijianglong skeleton is now housed in a local museum in Qijiang. “China is home to the ancient myths of dragons,” says Miyashita. “I wonder if the ancient Chinese stumbled upon a skeleton of a long-necked dinosaur like Qijianglong and pictured that mythical creature.” – See more at: http://uofa.ualberta.ca/news-and-events/newsarticles/2015/january/long-necked-dragon-discovered-in-china#sthash.ZCpknCAJ.dpuf

    See the full article here.

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    UAlberta’s daring and innovative spirit inspires faculty and students to advance knowledge through research, seek innovation in teaching and learning, and find new ways to serve the people of Alberta, the nation, and the world.

    The University of Alberta’s has had the vision to be one of the world’s great universities for the public good since its inception. This university is dedicated to the promise made by founding president Henry Marshall Tory that “… knowledge shall not be the concern of scholars alone. The uplifting of the whole people shall be its final goal.”

     
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