Tag: History

Catalogue of genetic differences between woolly mammoths and elephants reveals how ice-age giants braved the cold. Unlike their elephant cousins, woolly mammoths were creatures of the cold, with long hairy coats, thick layers of fat and small ears that kept heat loss to a minimum. For the first time, scientists have comprehensively catalogued the hundreds of genetic mutations that gave rise to these differences. The research reveals how woolly mammoths (Mammuthus primigenius) evolved from the ancestor they share with Asian elephants (Elephas maximus). It could even serve as a recipe for engineering elephants that are able to survive in Siberia

“These are genes we would need to alter in an elephant genome to create an animal that was mostly an elephant, but actually able to survive somewhere cold,” says Beth Shapiro, an evolutionary geneticist at the University of California, Santa Cruz who was not involved in the latest research. As fanciful as it sounds, such an effort is at a very early stage in a research lab in Boston, Massachusetts. The first woolly mammoth genome was published in 2008, but it contained too many errors to reliably distinguish how the mammoth genome differs from those of elephants. Other studies singled out individual mammoth genes for close inspection, identifying mutations that would have endowed the animals with light coats and oxygen-carrying haemoglobin proteins that work in the cold.

In the latest study, Vincent Lynch, an evolutionary geneticist at the University of Chicago in Illinois, and his team describe how they sequenced the genomes of three Asian elephants and two woolly mammoths (one died 20,000 years ago, another 60,000 years ago) to a very high quality. They found about 1.4 million DNA letters that differ between mammoths and elephants, which altered the sequence of more than 1,600 protein-coding genes. The study was posted on the biology preprint server bioRxiv.org on 23 April.

Combing the literature for information about what those proteins do in other organisms revealed dozens of genes implicated in skin and hair development, fat storage and metabolism, temperature sensation and other aspects of biology potentially relevant to life in the Arctic. For instance, several of the genes with changes unique to the mammoths were involved in setting the circadian clock, a potential adaptation to living in a world with dark winters and 24 hours of daylight in summer. Other Arctic animals such as some reindeer have similar mutations. The mammoth genomes also contained extra copies of a gene that controls the production of fat cells and variations in genes linked to insulin signalling, which are in turn linked to diabetes and diabetes prevention. And several of the genes that differ between mammoths and elephants are involved in sensing heat and transmitting that information to the brain.

The team ‘resurrected’ the mammoth version of one of the heat-sensing genes, which encodes a protein called TRPV3 that is expressed in skin and also regulates hair growth. They inserted the gene sequence into the genomes of human cells in the lab and exposed them to different temperatures, revealing that the mammoth TRPV3 protein is less responsive to heat than the elephant version is. The result chimes with a previous finding that mice with a deactivated version of TRPV3 are more likely to spend time in colder parts of their cage compared with normal rodents, and boast wavier hair. The next step, says Lynch, is to insert the same gene into elephant cells that have been chemically programmed to behave like embryonic cells, and so can be turned into a variety of cell types. Such induced pluripotent stem (iPS) cells could then be used to examine expression of mammoth proteins in different tissues. Lynch’s team also plans to test the effects of other mammoth mutations in iPS cells.

Similar work is already being carried out in the lab of George Church, a geneticist at Harvard Medical School in Boston. Using a technology known as CRISPR/Cas9 that allows genes to be easily edited, his team claims to have engineered elephant cells that contain the mammoth version of 14 genes potentially involved in cold tolerance — although the team has not yet tested how this affects the elephant cells. Church plans to do these experiments in “organoids” created from elephant iPS cells. The work, says Church, is a preamble to editing an entire woolly mammoth genome — and perhaps even resurrecting the woolly mammoth, or at least giving an Asian elephant enough mammoth genes to survive in the Arctic. The second option would be easier to do because it would require fewer mutations than the first option. A 16-square-kilometre reserve in north Siberia, known as Pleistocene Park, has even been proposed as a potential home for such a population of cold-tolerant elephants.

However, whether anyone would want to do such a thing is a different question, says Lynch, and Shapiro agrees. In her book How to Clone a Mammoth (Princeton University Press, 2015), she outlines the innumerable hurdles that stand in the way of breeding genetically modified ‘woolly elephants’ — from the ethics of applying reproductive technologies to an endangered species to the fact that the field of elephant reproductive biology is still immature.

“I probably should have called the book How One Might Go About Cloning a Mammoth (Should It Become Technically Possible, And If It Were, In Fact, a Good Idea, Which It’s Probably Not),” Shapiro says. “But that was a much less compelling title.”

Nature 521, 18–19 (07 May 2015) doi:10.1038/nature.2015.174

http://www.nature.com/news/index.html Nature

http://www.nature.com/news/mammoth-genomes-provide-recipe-for-creating-arctic-elephants-1.17462 Original web page at Nature

Although closely related to the notorious carnivore Tyrannosaurus rex, a new lineage of dinosaur discovered in Chile is proving to be an evolutionary jigsaw puzzle, as it preferred to graze upon plants. Palaeontologists are referring to Chilesaurus diegosuarezi as a ‘platypus’ dinosaur because of its bizarre combination of characters that resemble different dinosaur groups. For example, Chilesaurus boasted a proportionally small skull, hands with two fingers like Tyrannosaurus rex and feet more akin to primitive long-neck dinosaurs. Chilesaurus diegosuarezi is nested within the theropod group of dinosaurs, the dinosaurian group that gathers the famous meat eaters Velociraptor, Carnotaurus and Tyrannosaurus, and from which birds today evolved. The presence of herbivorous theropods was up until now only known in close relatives of birds, but Chilesaurus shows that a meat-free diet was acquired much earlier than thought.

Chilesaurus diegosuarezi is named after the country where it was collected, as well as honouring Diego Suárez, the seven year old boy who discovered the bones. He discovered the fossil remains of this creature at the Toqui Formation in Aysén, south of Chilean Patagonia, in rocks deposited at the end of the Jurassic Period, approximately 145 million years ago. Diego was in the region with his parents, Chilean geologists Manuel Suarez and Rita de la Cruz, who were studying rocks in the Chilean Patagonia, with the aim to better understand the formation of the Andes mountain range. Diego stumbled across the fossils while him and his sister, Macarena, were looking for decorative stones. Due to Chilesaurus‘ unusual combination of characters, it was initially thought that Diego had uncovered several species. However, since Diego’s find, more than a dozen Chilesaurus specimens have been excavated, including four complete skeletons — a first for the Jurassic Period in Chile — and they demonstrate that this dinosaur certainly combined a variety of unique anatomical traits.

Most of the specimens are the size of a turkey, but some isolated bones reveal that the maximum size of Chilesaurus was around three metres long. Chilean and Argentinian palaeontologists from institutions including the University of Birmingham, along with Diego’s parents, have been studying these skeletons, with the findings published in full in Nature on April 27th. Other features present in very different groups of dinosaurs Chilesaurus adopted were robust forelimbs similar to Jurassic theropods such as Allosaurus, although its hands were provided with two blunt fingers, unlike the sharp claws of fellow theropod Velociraptor. Chilesaurus‘ pelvic girdle resembles that of the ornithischian dinosaurs, whereas it is actually classified in the other basic dinosaur division — Saurischia. The different parts of the body of Chilesaurus were adapted to a particular diet and way of life, which was similar to other groups of dinosaurs. As a result of these similar habits, different regions of the body of Chilesaurus evolved resembling those present in other, unrelated groups of dinosaurs, which is a phenomenon called evolutionary convergence.

Chilesaurus represents one of the most extreme cases of mosaic convergent evolution recorded in the history of life. For example, the teeth of Chilesaurus are very similar to those of primitive long-neck dinosaurs because they were selected over millions of years as a result of a similar diet between these two lineages of dinosaurs. Martín Ezcurra, Researcher, School of Geography, Earth and Environmental Sciences, University of Birmingham said: ‘Chilesaurus can be considered a ‘platypus’ dinosaur because different parts of its body resemble those of other dinosaur groups due to mosaic convergent evolution. In this process, a region or regions of an organism resemble others of unrelated species because of a similar mode of life and evolutionary pressures. Chilesaurus provides a good example of how evolution works in deep time and it is one of the most interesting cases of convergent evolution documented in the history of life. ‘Chilesaurus shows how much data is still completely unknown about the early diversification of major dinosaur groups. This study will force palaeontologists to take more care in the future in the identification of fragmentary or isolated dinosaur bones. It comes as false relationship evidence may arise because of cases of convergent evolution, such as that present in Chilesaurus.’

Dr. Fernando Novas, Bernardino Rivadavia Natural Sciences Museum, Buenos Aires, Argentina, led the research on Chilesaurus and said: ‘Chilesaurus is the first complete dinosaur from the Jurassic Period found in Chile and represents one of the most complete and anatomically correct documented theropod dinosaurs from the southern hemisphere. Although plant-eating theropods have been recorded in North America and Asia, this is the first time a theropod with this characteristic has been found in a southern landmass. Chilesaurus was an odd plant-eating dinosaur only to be found in Chile. However, the recurrent discovery in beds of the Toqui Formation of its bones and skeletons clearly demonstrates that Chilesaurus was, by far, the most abundant dinosaur in southwest Patagonia 145 million years ago.’

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/04/150427124631.htm

Original web page at Science Daily

Although well known as one of the most iconic dinosaurs, Brontosaurus (the ‘thunder lizard’) has long been considered misclassified. Since 1903, the scientific community has believed that the genus Brontosaurus was in fact the Apatosaurus. Now, an exhaustive new study by palaeontologists from Portugal and the UK provides conclusive evidence that Brontosaurus is distinct from Apatosaurus and as such can now be reinstated as its own unique genus.
Although well known as one of the most iconic dinosaurs, Brontosaurus (the ‘thunder lizard’) has long been considered misclassified. Since 1903, the scientific community has believed that the genus Brontosaurus was in fact the Apatosaurus.

Now, an exhaustive new study by palaeontologists from Portugal and the UK provides conclusive evidence that Brontosaurus is distinct from Apatosaurus and as such can now be reinstated as its own unique genus. Brontosaurus is one of the most charismatic dinosaurs of all time, inspiring generations of children thanks to its size and evocative name. However, as every armchair palaeontologist knows, Brontosaurus was in fact a misnomer, and it should be correctly referred to as Apatosaurus. At least, this is what scientists have believed since 1903, when it was decided that the differences between Brontosaurus excelsus and Apatosaurus were so minor that it was better to put them both in the same genus. Because Apatosaurus was named first, it was the one that was used under the rules of scientific naming.

In fact, of course, the Brontosaurus was never really gone — it was simply treated as a species of the genus Apatosaurus: Apatosaurus excelsus. So, while scientists thought the genus Brontosaurus was the same as Apatosaurus, they always agreed that the species excelsus was different from other Apatosaurus species. Now, palaeontologists Emanuel Tschopp, Octávio Mateus, and Roger Benson say that Brontosaurus was a unique genus all along. But let’s start from the beginning. The history of Brontosaurus is complex, and one of the most intriguing stories in science. In the 1870s, the Western United States formed the location for dozens of new finds of fossil species, most notably of dinosaurs. Field crews excavated numerous new skeletons mostly for the famous and influential palaeontologists Marsh and Cope. During that period, Marsh’s team discovered two enormous, partial skeletons of long-necked dinosaurs and shipped them to the Yale Peabody Museum in New Haven, where Marsh worked. Marsh described the first of these skeletons as Apatosaurus ajax, the “deceptive lizard” after the Greek hero Ajax.

Two years later, he named the second skeleton Brontosaurus excelsus, the “noble thunder lizard.” However, because neither of the skeletons were found with a skull, Marsh reconstructed one for Brontosaurus excelsus. Brontosaurus was a massive animal, like Apatosaurus, and like another long-necked dinosaur from the Western United States, Camarasaurus. Because of this similarity, it seemed logical at the time that Brontosaurus had a similarly stout, box-like skull to that of Camarasaurus. However, this reconstruction was later found to be wrong. Shortly after Marsh’s death, a team from the Field Museum of Chicago found another skeleton similar to both Apatosaurus ajax and Brontosaurus excelsus. In fact, this skeleton was intermediate in shape in many aspects. Therefore, palaeontologists thought that Brontosaurus excelsus was actually so similar to Apatosaurus ajax that it would be more correct to treat them as two different species of the same genus. It was the second extinction of Brontosaurus — a scientific one: from now on, Brontosaurus excelsus became known as Apatosaurus excelsus and the name Brontosaurus was not considered scientifically valid any more. The final blow to “Brontosaurus” happened in the 1970s, when researchers showed that Apatosaurus was not closely related to Camarasaurus, but to yet another dinosaur from the same area: Diplodocus. Because Diplodocus had a slender, horse-like skull, Apatosaurus and thus also “Brontosaurus” must have had a skull more similar to Diplodocus instead of to Camarasaurus — and so the popular, but untrue myth about “Brontosaurus” being an Apatosaurus with the wrong head was born.

But now, in a new study published in the peer reviewed open access journal PeerJ and consisting of almost 300 pages of evidence, a team of scientists from Portugal and the UK have shown that Brontosaurus was distinct from Apatosaurus after all — the thunder lizard is back! How can a single study overthrow more than a century of research? “Our research would not have been possible at this level of detail 15 or more years ago,” explains Emanuel Tschopp, a Swiss national who led the study during his PhD at Universidade Nova de Lisboa in Portugal, “in fact, until very recently, the claim that Brontosaurus was the same as Apatosaurus was completely reasonable, based on the knowledge we had.” It is only with numerous new findings of dinosaurs similar to Apatosaurus and Brontosaurus in recent years that it has become possible to undertake a detailed reinvestigation of how different they actually were.

In science, the distinction between species and genera is without clear rules. Does this mean that the decision to resurrect Brontosaurus is just a matter of personal preference? “Not at all,” explains Tschopp, “we tried to be as objective as possible whenever making a decision which would differentiate between species and genus.” The researchers applied statistical approaches to calculate the differences between other species and genera of diplodocid dinosaurs, and were surprised by the result. “The differences we found between Brontosaurus and Apatosaurus were at least as numerous as the ones between other closely related genera, and much more than what you normally find between species,” explained Roger Benson, a co-author from the University of Oxford. Therefore, Tschopp and colleagues have concluded that it is now possible to resurrect Brontosaurus as a genus distinct from Apatosaurus. “It’s the classic example of how science works,” said Professor Mateus, a collaborator on the research. “Especially when hypotheses are based on fragmentary fossils, it is possible for new finds to overthrow years of research.” Science is a process, always moving towards a clearer picture of the world around us. Sometimes this also means that we have to step backwards a bit before we continue to advance. That’s what keeps the curiosity going. Hence, it is fitting that the Brontosaurus which sparked the curiosity of millions of people worldwide has now returned to do so again.

http://www.sciencedaily.com/ Science Daily

http://www.sciencedaily.com/releases/2015/04/150407085256.htm Original web page at Science Daily

A new analysis of geologic history may help solve the riddle of the “Cambrian explosion,” the rapid diversification of animal life in the fossil record 530 million years ago that has puzzled scientists since the time of Charles Darwin. A paper by Ian Dalziel of The University of Texas at Austin’s Jackson School of Geosciences, published in the November issue of Geology, a journal of the Geological Society of America, suggests a major tectonic event may have triggered the rise in sea level and other environmental changes that accompanied the apparent burst of life. The Cambrian explosion is one of the most significant events in Earth’s 4.5-billion-year history. The surge of evolution led to the sudden appearance of almost all modern animal groups. Fossils from the Cambrian explosion document the rapid evolution of life on Earth, but its cause has been a mystery. The sudden burst of new life is also called “Darwin’s dilemma” because it appears to contradict Charles Darwin’s hypothesis of gradual evolution by natural selection. “At the boundary between the Precambrian and Cambrian periods, something big happened tectonically that triggered the spreading of shallow ocean water across the continents, which is clearly tied in time and space to the sudden explosion of multicellular, hard-shelled life on the planet,” said Dalziel, a research professor at the Institute for Geophysics and a professor in the Department of Geological Sciences. Beyond the sea level rise itself, the ancient geologic and geographic changes probably led to a buildup of oxygen in the atmosphere and a change in ocean chemistry, allowing more complex life-forms to evolve, he said. The paper is the first to integrate geological evidence from five present-day continents — North America, South America, Africa, Australia and Antarctica — in addressing paleogeography at that critical time. Dalziel proposes that present-day North America was still attached to the southern continents until sometime into the Cambrian period. Current reconstructions of the globe’s geography during the early Cambrian show the ancient continent of Laurentia — the ancestral core of North America — as already having separated from the supercontinent Gondwanaland. In contrast, Dalziel suggests the development of a deep oceanic gateway between the Pacific and Iapetus (ancestral Atlantic) oceans isolated Laurentia in the early Cambrian, a geographic makeover that immediately preceded the global sea level rise and apparent explosion of life.

“The reason people didn’t make this connection before was because they hadn’t looked at all the rock records on the different present-day continents,” he said. The rock record in Antarctica, for example, comes from the very remote EllsworthMountains. “People have wondered for a long time what rifted off there, and I think it was probably North America, opening up this deep seaway,” Dalziel said. “It appears ancient North America was initially attached to Antarctica and part of South America, not to Europe and Africa, as has been widely believed.” Although the new analysis adds to evidence suggesting a massive tectonic shift caused the seas to rise more than half a billion years ago, Dalziel said more research is needed to determine whether this new chain of paleogeographic events can truly explain the sudden rise of multicellular life in the fossil record. “I’m not claiming this is the ultimate explanation of the Cambrian explosion,” Dalziel said. “But it may help to explain what was happening at that time.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/11/141101173229.htm Original web page at Science Daily

More than one hundred and fifty years ago, Charles Darwin hypothesized that species could cross oceans and other vast distances on vegetation rafts, icebergs, or in the case of plant seeds, in the plumage of birds. Though many were skeptical of Darwin’s “jump dispersal” idea, a new study suggests that Darwin might have been correct. A new computational method, published in the journal Systematic Biology, tested two competing theories about how species came to live where they do and found strong evidence for jump dispersal, especially for island species. The question of how species came to live where they live, which is studied by the field of biogeography, has long been debated among biologists, especially in cases where organisms that are related live on distant continents separated by vast oceans. Examples are flightless birds like the African ostrich and the Australian emu and Southern Beeches, a genus of 36 species of trees and shrubs which appear in temperate forests from South America to Australia and New Zealand. Others found Darwin’s “jump dispersal” theory too fanciful and suggested instead that “land bridges” were used when islands were contiguous. This view, called “vicariance biogeography,” became the dominant paradigm. In fact, the vicariance view became so dominant that computer programs designed to estimate the biogeographic history of a species left out jump dispersal entirely, and these programs have been used in hundreds of studies in recent years. Yet, in many cases, statistical dating of evolutionary events indicated that the breakup of land masses occurred tens of millions of years before some species’ ancestors evolved, bringing into question the validity of vicariance methods. The new study compares the theories of jump dispersal and vicariance in a new computational program developed by Nicholas J. Matzke, a postdoctoral fellow at the National Institute for Mathematical and Biological Synthesis. Using data from many species that live on the Hawaiian Islands and on other archipelagos, Matzke found that jump dispersal was able to explain the biogeography of the species with a far greater statistical probability than through the vicariance method. “Conventional biogeography said vicariance was a more scientific explanation than jump dispersal because vicariance relied on normal, predictable processes, and jump dispersal relied on extremely rare, near-miraculous events,” Matzke said. “Now the shoe is really on the other foot because the jump dispersal pattern appears to be much more common. It looks like Darwin was right after all.” Matzke suggests that researchers need to include jump dispersal in order to accurately reconstruct evolutionary history. “Jump dispersal helps us remember that events that are rare on human timescales can be common over geological timescales, and that biodiversity might be structured largely by these rare chance events.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/10/141001102729.htm  Original web page at Science Daily

The most comprehensive family tree of meat-eating dinosaurs ever created is enabling scientists to discover key details of how birds evolved from them. The study, published in the journal Current Biology, shows that the familiar anatomical features of birds — such as feathers, wings and wishbones — all first evolved piecemeal in their dinosaur ancestors over tens of millions of years. However, once a fully functioning bird body shape was complete, an evolutionary explosion began, causing a rapid increase in the rate at which birds evolved. This led eventually to the thousands of avian species that we know today. A team of researchers, led by the University of Edinburgh (UK) and including Swarthmore College Associate Professor of Statistics Steve C. Wang, examined the evolutionary links between ancient birds and their closest dinosaur relatives. They did this by analyzing the anatomical make-up of more than 850 body features in 150 extinct species and used statistical techniques to analyze their findings and assemble a detailed family tree. Based on their findings from fossil records, researchers say the emergence of birds some 150 million years ago was a gradual process, as some dinosaurs became more bird-like over time. This makes it very difficult to draw a dividing line on the family tree between dinosaurs and birds. Findings from the study support a controversial theory proposed in the 1940s that the emergence of new body shapes in groups of species could result in a surge in their evolution. “The evolution of birds from their dinosaur ancestors was a landmark in the history of life,” says Wang. “This process was so gradual that if you traveled back in time to the Jurassic, you’d find that the earliest birds looked indistinguishable from many other dinosaurs.” Wang invented a novel statistical method that was able to take advantage of new kinds of data from the fossil record, which reached the conclusion that early birds had a high rate of evolution. He adds that “birds as we know them evolved over millions of years, accumulating small shifts in shape and function of the skeleton. But once all these pieces were in place to form the archetypal bird skeleton, birds then evolved rapidly, eventually leading to the great diversity of species we know today.” “There was no moment in time when a dinosaur became a bird, and there is no single missing link between them, ” says Steve Brusatte of the University of Edinburgh’s School of GeoSciences, who led the study. “What we think of as the classic bird skeleton was pieced together gradually over tens of millions of years. Once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/09/140925130506.htm  Original web page at Science Daily

As Charles Darwin cruised the world on the HMS Beagle, he had access to an unusually well-stocked 400-volume library. That collection, which contained the observations of numerous other naturalists and explorers, has now been recreated online. As of today, all of more than 195,000 pages and 5000 illustrations from the works are available for the perusal of scholars and armchair naturalists alike, thanks to the Darwin Online project. The Beagle’s library included such influential reference texts as Charles Lyell’s Principles of Geology, as well as the writings of James Cook, Alexander von Humboldt, and Thomas Pennant (from whose 1793 book, History of Quadrupeds, this picture of a camel is taken). Atlases and books on travel, natural history, and geology made up most of the collection. But it had a few works of literature as well, including John Milton’s Paradise Lost. The Beagle library was dispersed when the voyage ended in October 1836. Scholars had previously identified 132 works as probably in the library based on Darwin’s writings. Science historian John van Wyhe, of the National University of Singapore, identified additional likely volumes by scouring Darwin’s field notebooks and the writings of other crew members for hints. The entire library—181 works in 404 volumes—includes works with illustrations digitized for the first time. Read more: http://darwin-online.org.uk/BeagleLibrary/Beagle_Library_Introduction.htm

http://www.sciencemag.org/ Science Magazine

http://news.sciencemag.org/evolution/2014/07/darwins-ship-library-goes-online?rss=1  Original web page at Science Magazine