Feedback and Notes

Due to Ning (our Web hosting company) being bought recently from the ashes of Mode Media we often experience 500 connection errors. Our apologies but these errors are out of our control. Hopefully, this will improve as the new company gains experience. Regards, AU

We are a worldwide social network of freethinkers, atheists, agnostics and secular humanists.

Date of earliest animal life reset by 30 million years

http://www.sciencedaily.com/releases/2012/06/120628181725.htm

June 28, 2012

The discovery was made by U of A geologists Ernesto Pecoits and Natalie Aubet in Uruguay. They found fossilized tracks a centimeter-long, slug-like animal left behind 585 million years ago in silty, shallow-water sediment.

A team of U of A researchers determined that the tracks were made by a primitive animal called a bilaterian, which is distinguished from other non-animal, simple life forms by its symmetry -- its top side is distinguishable from its bottom side -- and a unique set of "footprints."

U of A paleontologist Murray Gingras says fossilized tracks indicate that the soft-bodied animal's musculature enabled it to move through the sediment on the shallow ocean floor. "The pattern of movement indicates an evolutionary adaptation to search for food, which would have been organic material in the sediment," he said.

There were no fossilized remains of a bilaterian's body, just its tracks. "Generally when we find tracks of a soft-bodied animal, it means there's no trace of the body because they fossilize under different conditions," said Gingras. "It's usually just the body or just the tracks, not both."

It took more than two years for the U of A team members to satisfy themselves and a peer review panel of scientists that they had the right age for the bilaterian fossils.

U of A geochronologist Larry Heaman was among a group that returned to Uruguay to collect more fossil samples locked in a layer of sandstone. Heaman says because the depositional age of the sandstone is difficult to determine, they focused their investigation on particles of granitic rock found invading the sandstone samples.

Heaman explains that the granitic rocks were put through the university's mass spectrometry equipment, a process in which samples are bombarded by laser beams and the resulting atom- to molecule-sized particles are analyzed and dated.

Over the course of his U of A career, Heaman has taken part in a number of breakthrough research projects involving fossils. Last year he got the attention of the paleontology world when he confirmed the surprising date of a fossilized dinosaur bone found in New Mexico. Using U of A equipment, Heaman determined that the bone came from a sauropod, a plant-eating dinosaur that was alive some 700,000 years after the mass-extinction event that many believe wiped out all dinosaur life on Earth.

Heaman says the challenge in dating the bilaterian fossil makes it stand out from his other work. "This was the top research accomplishment because it has more direct relevance to the evolution of life as we know it," he said. "It was such a team effort; any one of us on our own couldn't have done this."

Before the U of A bilaterian find, the oldest sign of animal life was dated at 555 million years ago, from a find made in Russia.

Kurt Konhauser, a U of A geomicrobiologist, says the team's discovery will prompt new questions about the timing of animal evolution and the environmental conditions under which they evolved.

"This research was a huge interdisciplinary effort and shows the depth of the research capabilities here at the U of A," said Konhauser. "The challenge brought the sciences of geology, paleontology, geomicrobiology and geochronology together to nail down the age of the fossils."

Konhauser explains that in the past, research into the earliest signs of animal life would typically shift the date back by a few million years, but the U of A's finding of 30 million years is a real breakthrough.

The U of A's research team includes Ernesto Pecoits, Natalie Aubet, Kurt Konhauser, Larry Heaman, Richard Stern and Murray Gingras. The research was published June 28 in the journal Science.

Share this story on FacebookTwitter, and Google:

Other social bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University of Alberta. The original article was written by Brian Murphy.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Ernesto Pecoits, Kurt O. Konhauser, Natalie R. Aubet, Larry M. Heaman, Gerardo Veroslavsky, Richard A. Stern, and Murray K. Gingras. Bilaterian Burrows and Grazing Behavior at >585 Million Years AgoScience, 29 June 2012 DOI:10.1126/science.1216295

Views: 3598

Replies to This Discussion

Native species fight back: First evidence of coevolution between invasive, native species

http://www.sciencedaily.com/releases/2012/06/120628174536.htm

June 28, 2012

ScienceDaily (June 28, 2012) — Invasive species such as kudzu, privet and garlic mustard can devastate ecosystems, and, until now, scientists had little reason to believe that native plants could mount a successful defense.

A new University of Georgia study shows that some native clearweed plants have evolved resistance to invasive garlic mustard plants -- and that the invasive plants appear to be waging a counterattack. The study, published in the early edition of the journalProceedings of the National Academy of Sciences, is thought to provide the first evidence of coevolution between native and invasive plant species.

"The implications of this study are encouraging because they show that the native plants aren't taking this invasion lying down," said study author Richard Lankau, assistant professor of plant biology in the UGA Franklin College of Arts and Sciences. "It suggests that if you were to take a longer view -- a timescale of centuries -- that exotic species could become integrated into their communities in a way that is less problematic for the natives."

Garlic mustard (Alliaria petiolata) was introduced to the U.S. from Europe roughly 150 years ago first in New York and Virginia and then to the Chicago area. The noxious plant continues to spread rapidly throughout the Northeast, Midwest and Southeast. "It's a pretty well-hated plant," Lankau said, because it can form dense carpets in forest understories and, even after being physically removed from an area, can reestablish itself within a year.

Much of the plant's success is a result of the chemical warfare it wages with a compound known as sinigrin, which kills fungi that help native plants extract nutrients from the soil. The chemical is relatively new to North America, and this novelty gives garlic mustard a huge competitive advantage.

Through a series of greenhouse and field experiments conducted over three years in five states, Lankau has shown that invasive garlic mustard produces more sinigrin in areas where more local plants are present. He found that native clearweed (Pilea pumila) plants, which were chosen for the study because they occupy the same forest understory habitat, show higher levels of resistance to sinigrin in areas where the two species have a longer history of coexistence.

"It looks like the native plants have evolved in response to the traits of the invader," Lankau said.

In addition to transplanting clearweed seeds back to their sites of origin, Lankau also planted them in all of the other study sites and monitored their growth. Each site has its unique soil chemistry and climate, and Lankau said he expected the plants to exhibit a home-field advantage. Instead, he found that native plants resistant to the invader did best in heavily invaded sites, regardless of where they originated. Surprisingly, he found that plants resistant to sinigrin actually did worse than their less-resistant-plant counterparts in areas where there was little or no garlic mustard.

"It's not all good for those populations that are evolving tolerance," Lankau said. "Because they are less successful in the absence of garlic mustard, their resistance to the invasive species comes at a cost."

Taken together, the findings suggest that the native and invasive species could reach equilibrium over a long period of time. Lankau said the study also raises the possibility that humans can help speed the adaptation of ecosystems to invasive species. He explained that removing invasive species and replanting natives often results in failure but replacing invasive species with native plants from an area where the plants have had time to adapt to the invader could be more effective. Rather than replanting clearweed from a recently invaded site in Michigan, for example, land managers could use plants from New York that are more likely to be resistant to garlic mustard.

"When people talk about evolution, it's usually in the past tense," Lankau said. "But one of the important messages from this study is that it's an ongoing process that can happen fast. And this study suggests that we might be able to jumpstart that process through evolutionarily informed management."

The research was supported by the National Science Foundation.

Share this story on FacebookTwitter, and Google:

Other social bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University of Georgia. The original article was written by Sam Fahmy.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. R. A. Lankau. Coevolution between invasive and native plants driven by chemical competition and soil biota.Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1201343109

Part of the genome of two hunter-gatherers from 7,000 years ago

http://www.sciencedaily.com/releases/2012/06/120628164428.htm

June 28, 2012

ScienceDaily (June 28, 2012) — A team of scientists, led by researcher Carles Lalueza-Fox from CSIC (Spanish National Research Council), has recovered -- for the first time in history -- part of the genome of two individuals who were alive in the Mesolithic Period, 7000 years ago.  The remains were found at La Braña-Arintero site, located at Valdelugueros (León), Spain.

The study results, published in the Current Biology, indicate that current Iberian populations do not come from these recently discovered humans.

The Mesolithic Period, framed between the Paleolithic and Neolithic Periods, is characterized by the advent of agriculture, coming from the Middle East.

The genome found is the oldest from Prehistory, 1,700 years before Ötzi, the Iceman lived.

Researchers have also recovered the complete mitochondrial DNA of one of these individuals, through which they could determine that European populations from Mesolithic Period were very uniform genetically. Carles Lauleza-Fox, from the Institute of Evolutionary Biology (CSIC-UPF), states: "These hunters-gatherers shared nomadic habits and had a common origin. Despite their geographical distance, individuals from the regions corresponding to the current England, Germany, Lithuania, Poland, and Spain, shared the same mitochondrial lineage."

The DNA data, which represent the 1.34% and the 0.5% of both individuals total genome, show that they are not directly connected to current populations of the Iberian Peninsula. Iberians from the Mesolithic Period were closer to current populations of northern Europe, who could have assimilated part of the genetic legacy of these hunters-gatherers.

La Braña-Arintero site was discovered in 2006 by chance. Juan Manuel Vidal Encinas, archeologist from the Regional Government of Castilla y León, who has also participated in the study, has excavated it at a later date. The cave, due to its location in a cold and mountainous area, is a suitable place for the good preservation of the DNA of these two individuals, found inside it.

The oldest remains from Prehistory

CSIC researcher emphasizes: "So far, we only had one genome of the European Prehistory, that of Ötzi [also known as the Iceman], from the Neolithic Period. His mummy, belonging to a man who lived 5300 years ago, was found in the Tyrolean Alps, on the border between Austria and Italy. La Braña-Arintero site offers a unique opportunity to obtain pre-Neolithic genomes."

According to Lalueza-Fox, this is only a first result since the intention of the team is to recover the complete DNA of these individuals, and to compare it with that of the modern humans. CSIC researcher discloses: "The arrival of the Neolithic Period brought about a replacement of populations, and could cause genetic changes in genes associated with new infectious diseases, and in metabolic genes linked to changes in diet. Therefore, all the information extracted from this genome will be absolutely important."

Share this story on FacebookTwitter, and Google:

Other social bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by Spanish National Research Council (CSIC), via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Federico Sánchez-Quinto, Hannes Schroeder, Oscar Ramirez, María C. Ávila-Arcos, Marc Pybus, Iñigo Olalde, Amhed M.V. Velazquez, María Encina Prada Marcos, Julio Manuel Vidal Encinas, Jaume Bertranpetit, Ludovic Orlando, M. Thomas P. Gilbert, Carles Lalueza-Fox. Genomic Affinities of Two 7,000-Year-Old Iberian Hunter-GatherersCurrent Biology, 2012; DOI: 10.1016/j.cub.2012.06.005

Slowly the blank lines of the story of life are being filled. A word here, a clause there then a sentence. 

ENJOYING NATURAL SELECTION ON MULTIPLE LEVELS

WilsonOver at Rationally Speaking, Leonard Finkelman on the Richard Dawkins-E.O. Wilson debate about levels of natural selection:

The so-called “selfish gene” theory, technically known as gene selection, is an elaboration of work done by W.D. Hamilton and G.C. Williams on a phenomenon known as “kin selection.” Kin selection is predicated on the idea that the impulse I feel to care for my nephew is stronger than the impulse I feel to care for (say) my neighbor’s nephew. I know that my nephew is my sister’s son, and that my sister and I were born of the same parents; I therefore know that he carries 50% of my sister’s genetic alleles, and that there’s a 50% chance that any one of my sister’s alleles is one that I also carry. For any one of my nephew’s alleles, then, there’s a 25% chance that I also carry that allele. If I care for my nephew, then my genes have a one in four chance of helping themselves; if I care for my neighbor’s nephew, the odds are much, much lower. Gene selectionists therefore argue that genes are the individuals who benefit in the process of natural selection. Hence Dawkins’ famous claim that organisms are “gigantic lumbering robots” for carrying genes around: I have an impulse to care for my nephew because it helps (some of) my genes, even though it hurts me as a whole.

In 2010, E.O. Wilson and two collaborators wrote an article in Nature attacking the viability of kin selection. We won’t get into the details of their mathematical argument; the bottom line is that things rarely work out so neatly as “my nephew has half of my sister’s genetic alleles and she has half of mine,” and the complexities ultimately call into question the idea that gene selection can explain altruistic behavior. In his newest book and a recent New York Times “Stone” column (interestingly, a philosophy blog!), Wilson proposes an alternative that he calls “multi-level selection.” His account is so called because Wilson believes that nature sometimes selects genes, sometimes selects organisms, and sometimes selects groups—and that the latter option is the one that explains altruism. It was this claim that prompted Dawkins’ scathing review of Wilson’s book, linked in the first paragraph. Undermining the very foundation of Dawkins’ account of selection probably had something to do with it, too.

 

Posted by Robin Varghese at 06:45 AM | Permalink

The Danger Of Creationism

Explained:

Rejecting evolution expresses more than an inability to think critically; it relies on a fundamentally paranoid worldview. Think what the world would have to be like for evolution to be false. Almost every scientist on earth would have to be engaged in a fraud so complex and extensive it involved every field from archaeology, paleontology, geology and genetics to biology, chemistry and physics. And yet this massive concatenation of lies and delusion is so full of obvious holes that a pastor with a Bible-college degree or a homeschooling parent with no degree at all can see right through it.

Fred Clark suggests an alternative way to square the creationist circle:

Theory No. 2 doesn’t blame the scientists. It blames God. This conspiracy theory says that God is lying. This involves some variation of the Omphalos hypothesis, meaning the belief that the apparent age of the world is not its actual age. The idea here is that God simply created the world to appear far older than it is. ... To believe in creationism, either you must believe that there is a global conspiracy of scientists intent on lying to you, or you must believe that God is intent on lying to you. That 46 percent of Americans believe one or the other of those is, as I said, dismaying.

Earlier Dish on creationism here and here.

Mass extinctions reset the long-term pace of evolution

http://www.sciencedaily.com/releases/2012/07/120702134826.htm

July 2, 2012

ScienceDaily (July 2, 2012) — A new study indicates that mass extinctions affect the pace of evolution, not just in the immediate aftermath of catastrophe, but for millions of years to follow. The study's authors, University of Chicago's Andrew Z. Krug and David Jablonski, will publish their findings in the August issue of the journal Geology.

Scientists expected to see an evolutionary explosion immediately following a mass extinction, but Krug and Jablonski's findings go far beyond that.

"There's some general sense that the event happens, there's some aftermath and then things return to normal," said Krug, a research scientist in geophysical sciences at UChicago. But in reality, Krug said, "Things don't return to what they were before. They operate at a different pace, sometimes more rapidly, other times more slowly. Evolutionary rates shift, and that shift is permanent until the next mass extinction."

Krug and Jablonski's suggestion that the potential for rapid speciation and expansion of survivors and new groups of organisms in the "emptier" world following a mass extinction "is a reasonable possibility as one source of rate change," said paleontologist Richard Bambach of the Smithsonian Museum of Natural History, who was not directly involved in the UChicago study.

The long-term evolutionary patterns of species diversification following mass extinctions are poorly understood. Paleontologists have extensively debated whether diversity has increased over the last 251 million years, which followed the most devastating mass extinction in Earth history, Bambach said

Inconsistent classifications

Scientists have been putting Latin names on fossils since 1758, often inconsistently. Methods and tools have changed with the times, but old names often remain. The UChicago paleontologists have combed through seemingly endless volumes of research papers and countless museum drawers in an ongoing attempt to standardize these classifications.

For their Geology study, Krug and Jablonski analyzed contemporary groups of organisms from the end of the Pleistocene Epoch, which ended approximately 10,000 years ago, to the Jurassic Period, which began approximately 200 million years ago. The availability of globally abundant data on bivalves, a group that includes clams, oysters and scallops, set the study's time boundaries.

"With some groups, like sea urchins or corals, you just couldn't do it because the numbers aren't big enough," said Jablonski, the William R. Kenan Jr. Distinguished Service Professor in Geophysical Sciences. When he and Krug statistically plotted the origination rate of new bivalve species at 50 million-year intervals, they found that all the species evolved at a fairly steady rate for millions of years. Then the bivalve groups show a sudden increase or decrease in the rates at which new species evolved. These sudden shifts marked the occurrence of a mass extinction. "They settle back down to a different rate from what was before, and they do it multiple times, corresponding to each mass extinction," Jablonski said.

Theoretically, the origination rates of the organisms might have "been all over the map," with evolutionary rates varying in a random or chaotic style, but they didn't. "It's surprising how organized the pattern is," he said.

Krug and Jablonski's perspective of the data is somewhat different from Bambach's. These perspectives are "not contradictory, but complementary, ways of looking at the data," Bambach said. "One of the valuable things about their work is that they record the pattern and pattern change during intervals that I lump together."

Bambach bases his work on older data compilations that include the animal kingdom as a whole, while Krug and Jablonski use their new, carefully vetted data from bivalve mollusks.

Setting a new pace

"There's been a lot of talk about the evolutionary role of mass extinctions, but it's like the weather. Everyone talks about it, but no one does much about it," Jablonski joked.

"No one has really thought about it in terms of these downstream dynamics, once the smoke has cleared and ecosystems have found a new equilibrium, for want of a better word. But the wonderful thing is that when they find a new equilibrium, it's a different evolutionary pace from the one that prevailed for the preceding 50 million years. The survivors of the mass extinction, or the world they inherited, is so different from what went before that the rate of evolution is permanently changed."

Krug and Jablonski's research builds upon the work of UChicago's David Raup, the Sewell L. Avery Distinguished Service Professor Emeritus in Geophysical Sciences, and Michael Foote, professor in Geophysical Sciences.

In 1978, Raup published a method for determining the extinction rate of organisms. His method involved monitoring the survivorship of a group of organisms that had all originated during a specific time period and quantifying when they disappeared. It would be like collecting census data for all individuals born on Jan. 1, 1899, tracking their longevity, then finding that the 1918 influenza epidemic had produced a spike in this group's mortality.

Foote followed up in 2001, showing that Raup's method worked equally well for determining origination rates as it did for extinction rates. One simply needed to use the method in reverse, tracking the time since origination of a group of co-occurring lineages as opposed to the time until extinction. Now comes Krug and Jablonski's latest study, finding that the evolutionary "birth rate" was also reset at major catastrophes. "It's very Chicago-esque," Jablonski said.

Share this story on FacebookTwitter, and Google:

Other social bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University of Chicago, via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Andrew Z. Krug and David Jablonski. Long-term origination rates are re-set only at mass extinctionsGeology, June 29, 2012

Newly discovered dinosaur implies greater prevalence of feathers; Megalosaur fossil represents first feathered dinosaur not closely related to birds

http://www.sciencedaily.com/releases/2012/07/120702210225.htm

July 3, 2012

ScienceDaily (July 2, 2012) — A new species of feathered dinosaur discovered in southern Germany is further changing the perception of how predatory dinosaurs looked. The fossil of Sciurumimus albersdoerferi,which lived about 150 million years ago, provides the first evidence of feathered theropod dinosaurs that are not closely related to birds.

The fossil is described in a paper published in the Proceedings of the National Academy of Sciences on July 2.

"This is a surprising find from the cradle of feathered dinosaur work, the very formation where the first feathered dinosaurArchaeopteryx was collected over 150 years ago," said Mark Norell, chair of the Division of Palaeontology at the American Museum of Natural History and an author on the new paper along with researchers from Bayerische Staatssammlung für Paläontologie und Geologie and the Ludwig Maximilians University.

Theropods are bipedal, mostly carnivorous dinosaurs. In recent years, scientists have discovered that many extinct theropods had feathers. But this feathering has only been found in theropods that are classified as coelurosaurs, a diverse group including animals likeT. rexand birds. Sciurumimus -- identified as a megalosaur, nota coelurosaur -- is the first exception to this rule. The new species also sits deep within the evolutionary tree of theropods, much more so than coelurosaurs, meaning that the species that stem from Sciurumimus are likely to have similar characteristics.

"All of the feathered predatory dinosaurs known so far represent close relatives of birds," said palaeontologist Oliver Rauhut, of the Bayerische Staatssammlung für Paläontologie und Geologie. "Sciurumimus is much more basal within the dinosaur family tree and thus indicates that all predatory dinosaurs had feathers."

The fossil, which is of a baby Sciurumimus, was found in the limestones of northern Bavaria and preserves remains of a filamentous plumage, indicating that the whole body was covered with feathers. The genus name ofSciurumimus albersdoerferirefers to the scientific name of the tree squirrels,Sciurus, and means "squirrel-mimic"-referring to the especially bushy tail of the animal. The species name honours the private collector who made the specimen available for scientific study.

"Under ultraviolet light, remains of the skin and feathers show up as luminous patches around the skeleton," said co-author Helmut Tischlinger, from the Jura Museum Eichstatt.

Sciurumimusis not only remarkable for its feathers. The skeleton, which represents the most complete predatory dinosaur ever found in Europe, allows a rare glimpse at a young dinosaur. Apart from other known juvenile features, such as large eyes, the new find also confirmed other hypotheses.

"It has been suggested for some time that the lifestyle of predatory dinosaurs changed considerably during their growth," Rauhut said. "Sciurumimus shows a remarkable difference to adult megalosaurs in the dentition, which clearly indicates that it had a different diet."

Adult megalosaurs reached about 20 feet in length and often weighed more than a ton. They were active predators, which probably also hunted other large dinosaurs. The juvenile specimen of Sciurumimus, which was only about 28 inches in length, probably hunted insects and other small prey, as evidenced by the slender, pointed teeth in the tip of the jaws.

"Everything we find these days shows just how deep in the family tree many characteristics of modern birds go, and just how bird-like these animals were," Norell said. "At this point it will surprise no one if feather like structures were present in the ancestors of all dinosaurs.

The study was financed by the Volkswagen Foundation and the American Museum of Natural History.

Share this story on FacebookTwitter, and Google:

Other social bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by American Museum of Natural History.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Oliver W. M. Rauhut, Christian Foth, Helmut Tischlinger, and Mark A. Norell. Exceptionally preserved juvenile megalosauroid theropod dinosaur with filamentous integument from the Late Jurassic of Germany.Proceedings of the National Academy of Sciences, July 2, 2012 DOI: 10.1073/pnas.1203238109

Native American populations descend from three key migrations

http://www.sciencedaily.com/releases/2012/07/120711134710.htm

July 11, 2012

ScienceDaily (July 11, 2012) — Scientists have found that Native American populations -- from Canada to the southern tip of Chile -- arose from at least three migrations, with the majority descended entirely from a single group of First American migrants that crossed over through Beringia, a land bridge between Asia and America that existed during the ice ages, more than 15,000 years ago.

By studying variations in Native American DNA sequences, the international team found that while most of the Native American populations arose from the first migration, two subsequent migrations also made important genetic contributions. The paper is published in the journal Nature July 11.

"For years it has been contentious whether the settlement of the Americas occurred by means of a single or multiple migrations from Siberia," said Professor Andres Ruiz-Linares (UCL Genetics, Evolution and Environment), who coordinated the study. "But our research settles this debate: Native Americans do not stem from a single migration. Our study also begins to cast light on patterns of human dispersal within the Americas."

In the most comprehensive survey of genetic diversity in Native Americans so far, the team took data from 52 Native American and 17 Siberian groups, studying more than 300,000 specific DNA sequence variations called Single Nucleotide Polymorphisms to examine patterns of genetic similarities and differences between the population groups.

The second and third migrations have left an impact only in Arctic populations that speak Eskimo-Aleut languages and in the Canadian Chipewyan who speak a Na-Dene language. However, even these populations have inherited most of their genome from the First American migration. Eskimo-Aleut speakers derive more than 50% of their DNA from First Americans, and the Chipewyan around 90%. This reflects the fact that these two later streams of Asian migration mixed with the First Americans they encountered after they arrived in North America.

"There are at least three deep lineages in Native American populations," said co-author David Reich, Professor of genetics at Harvard Medical School. "The Asian lineage leading to First Americans is the most anciently diverged, whereas the Asian lineages that contributed some of the DNA to Eskimo-Aleut speakers and the Na-Dene-speaking Chipewyan from Canada are more closely related to present-day East Asian populations."

The team also found that once in the Americas, people expanded southward along a route that hugged the coast with populations splitting off along the way. After divergence, there was little gene flow among Native American groups, especially in South America.

Two striking exceptions to this simple dispersal were also discovered. First, Central American Chibchan-speakers have ancestry from both North and South America, reflecting back-migration from South America and mixture of two widely separated strands of Native ancestry. Second, the Naukan and coastal Chukchi from north-eastern Siberia carry 'First American' DNA. Thus, Eskimo-Aleut speakers migrated back to Asia, bringing Native American genes.

The team's analysis was complicated by the influx into the hemisphere of European and African immigrants since 1492 and the 500 years of genetic mixing that followed. To address this, the authors developed methods that allowed them to focus on the sections of peoples' genomes that were of entirely Native American origin.

"The study of Native American populations is technically very challenging because of the widespread occurrence of European and African mixture in Native American groups," said Professor Ruiz-Linares.

"We developed a method to peel back this mixture to learn about the relationships among Native Americans before Europeans and Africans arrived," Professor Reich said, "allowing us to study the history of many more Native American populations than we could have done otherwise."

The assembly of DNA samples from such a diverse range of populations was only possible through a collaboration of an international team of 64 researchers from the Americas (Argentina, Bolivia, Brazil, Canada, Chile, Colombia, Costa Rica, Guatemala, Mexico, Peru, Russia and the USA), Europe (England, France, Spain and Switzerland) and Russia.

Share this story on FacebookTwitter, and Google:

Other social bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University College London, via EurekAlert!, a service of AAAS.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. David Reich, Nick Patterson, Desmond Campbell, Arti Tandon, Stéphane Mazieres, Nicolas Ray, Maria V. Parra, Winston Rojas, Constanza Duque, Natalia Mesa, Luis F. García, Omar Triana, Silvia Blair, Amanda Maestre, Juan C. Dib, Claudio M. Bravi, Graciela Bailliet, Daniel Corach, Tábita Hünemeier, Maria Cátira Bortolini, Francisco M. Salzano, María Luiza Petzl-Erler, Victor Acuña-Alonzo, Carlos Aguilar-Salinas, Samuel Canizales-Quinteros, Teresa Tusié-Luna, Laura Riba, Maricela Rodríguez-Cruz, Mardia Lopez-Alarcón, Ramón Coral-Vazquez, Thelma Canto-Cetina, Irma Silva-Zolezzi, Juan Carlos Fernandez-Lopez, Alejandra V. Contreras, Gerardo Jimenez-Sanchez, Maria José Gómez-Vázquez, Julio Molina, Ángel Carracedo, Antonio Salas, Carla Gallo, Giovanni Poletti, David B. Witonsky, Gorka Alkorta-Aranburu, Rem I. Sukernik, Ludmila Osipova, Sardana A. Fedorova, René Vasquez, Mercedes Villena, Claudia Moreau, Ramiro Barrantes, David Pauls, Laurent Excoffier, Gabriel Bedoya, Francisco Rothhammer, Jean-Michel Dugoujon, Georges Larrouy, William Klitz, Damian Labuda, Judith Kidd, Kenneth Kidd, Anna Di Rienzo, Nelson B. Freimer, Alkes L. Price, Andrés Ruiz-Linares. Reconstructing Native American population historyNature, 2012; DOI: 10.1038/nature11258

ScienceShot: Evolution in a Jiffy

on 17 July 2012, 7:01 PM |
sn-seastar.jpg
Credit: Jonathan Puritz

When a small group of sea star larvae got swept away from their parents off the coast of Australia thousands of years ago, they proved more resourceful than Tom Hanks in Cast Away. Rather than befriending a volleyball, the short-legged sea stars—called "cushion stars" for their plump shape—developed the ability to mate with themselves. Their evolution into live-bearing hermaphrodites is one of the fastest known examples of speciation among marine animals, say the authors of a study published online today in the Proceedings of the Royal Society B. To pinpoint when and where the sea stars broke away from their kin, the team analyzed DNA from the tissue of nearly 400 animals, half belonging to the ancestral species, Cryptasterina pentagona, and half to the new species, C. hystera. By analyzing the evolutionary relationships between the two species' DNA sequences, they were able to infer that C. hystera had broken away from the southern range of C. pentagonanear the Great Barrier Reef at most 22,000 years ago. By about 6000 years ago, C. hystera had become a distinct species—lightning-quick adaptation, by evolutionary standards.

Cueva de las Manos (Spanish for Cave of the Hands) is a cave or a series of caves located in the province of Santa Cruz, Argentina, 163 km (101 mi) south of the town of Perito Moreno. It is famous (and gets its name) for the paintings of hands. The art in the cave dates from 13,000 to 9,000 years ago.

Cueva de las Manos (Spanish for Cave of the Hands) is a cave or a series of caves located in the province of Santa Cruz, Argentina, 163 km (101 mi) south of the town of Perito Moreno. It is famous (and gets its name) for the paintings of hands. The art in the cave dates from 13,000 to 9,000 years ago.

RSS

© 2017   Created by Atheist Universe.   Powered by

Badges  |  Report an Issue  |  Privacy Policy  |  Terms of Service