Daily Archives: May 2, 2017

May 2, 2017 Two cichlid species (Orthochromis sp.) size each other up. Ancient hybridization events involving riverine and lacustrine cichlids may have given rise to species now endemic to Lake Tanganyika. Credit: U. Schliewen

Genetic studies of cichlid fishes suggest that interspecies hybrids played a prominent role in their evolution. Analysis of a unique fossil cichlid from the Upper Miocene of East Africa now provides further support for this idea.

The cichlids constitute one of the most diverse families of freshwater fishes in tropical habitats. Its members have adapted to the demands of a wide range of ecological niches, and many have developed highly specialized feeding habits. Contemporary representatives of the family therefore provide an ideal model system for evolutionary biologists who seek to understand the mechanisms that underlie the process of species diversification. Unfortunately, fossil specimens that could help to trace earlier phases of cichlid evolution are quite rare, and most are poorly preserved and/or fragmentary. Now scientists around Ludwig-Maximilians-Universitaet (LMU) in Munich paleontologist Professor Bettina Reichenbacher have described a new fossil cichlid discovered in Upper Miocene strata in East Africa, which provides new insights into the evolutionary history of the group. Moreover, the results are consistent with molecular genetic data relating to the ongoing diversification of the family in the Great Lakes region of East Africa, which have indicated that hybridization between members of related species or even genera has played a major role in cichlid speciation. The work also sheds light on the environmental conditions that prevailed in the Rift Valley of East Africa in the Upper Miocene period, 9-10 million years ago. The new findings appear in the Journal of Vertebrate Paleontology.

The authors assign the fossil to a newly defined genus and species (Tugenchromis pickfordi). In light of the scarcity of well-preserved cichlid fossils, the phylogenetic placement of the new specimen is dependent on comparisons with modern members of the familyand given the enormous diversity of the latter, this is by no means an easy task. However, in cooperation with Dr. Ulrich Schliewen (Zoological State Collections, Munich), Reichenbacher and her team have assembled a unique database on the morphology of present-day cichlids, in which all the lineages found in Lake Tanganyika are represented. This dataset is based on the painstaking analysis of X-ray photographs of the skeletons of 763 individuals belonging to 227 modern cichlid species. "This unique resource has made it possible for the first time to place a new fossil species securely within the phylogeny of African cichlids. Indeed, our analysis shows it to be a member of the most ancient cichlid lineage that contributed to the so-called East African Radiation, a spectacular burst of diversification that has given rise to a huge variety of species," Reichenbacher explains.

The new fossil displays a striking "mosaic-like" set of characters, combining traits that are typical for three distinct cichlid groups found in Lake Tanganyika today. "This combination of characters is particularly interesting, because molecular geneticists have shown that many of the cichlid species in Lake Tanganyika possess 'mosaic' genomesmade up of genetic material derived from non-related species. The mosaic of characters displayed by the fossil specimen is a reflection of the morphological consequences of such interspecies hybridization," says Dr. Melanie Altner, first author of the study.

The basin now occupied by Lake Tanganyika came into being at least 5.5 million years ago, and it has been assumed that the species radiation that gave rise to the striking diversity of cichlids in the lake was triggered by its formation. However, new models based on molecular genetic analyses of these cichlid species suggest that an radiationdriven in part by interspecies hybridization - was already underway in the rivers and lakes that drained into the Proto-Lake Tanganyika. "In fish, it is not uncommon for such hybrids, which display characters derived from both parental species, to be fertile and capable of producing fertile progeny," says Schliewen. During the Miocene and Pliocene periods, the climate of East Africa became more arid, and many feeder streams dried up. As a result, many cichlid species that had originated in riverine systems were isolated in Lake Tanganyika basin itself, which thus became a 'melting pot' for subsequent episodes of speciation to which these immigrant species contributed. "Our fossil supports the hypothesis that hybridizations played a more prominent role in cichlid speciation than was once thought - and that diversification of the cichlids now endemic to the lake did not begin in the lake itself," Reichenbacher says.

The new fossil also elucidates aspects of the environment in which Lake Tanganyika formed. It was discovered by Reichenbacher and her coworkers in Kenya's Tugen Hills, in the eastern arm of the East African Rift Valley, but Lake Tanganyikain which its closest relatives now liveis located in the Valley's western branch. The fossil therefore provides further evidence for a previously postulated hydrological connection between the eastern and western arms of the Rift Valley, which was subsequently severed as rifting progressed.

Explore further: Fish cooperate for selfish reasons

More information: Melanie Altner et al, , gen. et sp. nov., from the upper Miocenea stem-group cichlid of the 'East African Radiation', Journal of Vertebrate Paleontology (2017). DOI: 10.1080/02724634.2017.1297819

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Evolution: On mosaics and melting-pots - Phys.Org

Green's views and past statements are facing scrutiny ahead of his confirmation hearing, which has yet to be scheduled. If confirmed, Green wouldn't be the only prominent doctor and member of the Trump administration to reject evolution. HUD Secretary Ben Carson has also made similar arguments and once said the theory of evolution was encouraged by Satan.

Green, a Tennessee state senator, has faced opposition from Democrats and LGBT groups over his past anti-LGBT comments. In one comment, from September, Green said, "If you poll the psychiatrists, they're going to tell you that transgender is a disease."

The National Academy of Sciences says that the theory of evolution "is supported by so many observations and confirming experiments that scientists are confident that the basic components of the theory will not be overturned by new evidence."

The group adds, "Because the evidence supporting it is so strong, scientists no longer question whether biological evolution has occurred and is continuing to occur. Instead, they investigate the mechanisms of evolution, how rapidly evolution can take place, and related questions."

Green rejects the conclusions of scientists in his lecture. In his 2015 speech to a church to Cincinnati titled 'Isn't Evolution A Solution?, Green dedicated nearly an hour to explaining why his work as a medical doctor taught him to reject the theory.

Green claims that the theory of evolution violates physical law, using the example of a lawn mower left out in a backyard.

"The evolutionists have their bad argument, too," Green said. They say, 'Well, I can't explain how it went from this to incredibly complex, so it must have been billions of years.' That's kind of where they put their faith. The truth of the matter is is the second law of thermo fluid dynamics says that the world progresses from order to disorder not disorder to order.

"If you put a lawn mower out in your yard and a hundred years come back, it's rusted and falling apart. You can't put parts out there and a hundred years later it's gonna come back together. That is a violation of a law of thermodynamics. A physical law that exists in the universe."

Green also argues that processes allowing human life, such as blood-clotting, are 'irreducibly complex' and says that is evidence of a creator.

"Irreducible complexity is important in the argument for the creationist because of this: Evolution assumes a series of minuscule changes over time, and each change has to give a survival advantage to the organism. If it doesn't, and it causes a disadvantage the organism dies and evolution ends," Green said.

Later in the speech, Green adds, "The question is, did all of this happen by chance operating inside the laws of chemistry and physics? Or is this unbelievable engineering, and is the scientific mind going to look at it and make the conclusion, observation, and conclusion that it was created and not that it evolved. Again, remember time is not the hero of the plot. Time is the villain, because over time things break down, they don't assemble themselves together."

Green did not respond to a request for comment. A White House spokesperson told CNN's KFile that a spokesperson handling Green's nomination would contact them, but Green's spokesperson did not.

In a statement announcing his nomination in early April, Secretary of Defense Jim Mattis put his full support behind Green.

"He had my full support during the selection process, and he will have my full support during the Senate confirmation process. I am confident of Mark's ability to effectively lead the Army," Mattis said.

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Trump Army secretary pick gave a lecture arguing against the theory of evolution - CNN

May 2, 2017 Credit: CC0 Public Domain

Chickens were domesticated from Asian jungle fowl around 6000 years ago. Since domestication they have acquired a number of traits that are valuable to humans, including those concerning appearance, reduced aggression and faster egg-laying, although it is not known when and why these traits evolved.

Now, an international team of scientists has combined DNA data from archaeological chicken bones with statistical modeling to pinpoint when these traits started to increase in frequency in Europe.

"Ancient DNA allows us to observe how genes have changed in the past, but the problem has always been to get high enough time resolution to link genetic evolution to potential causes. But with enough data and a novel statistical framework, we now have timings that are precise enough to correlate them with ecological and cultural shifts." says Liisa Loog, the first author of the study.

To their surprise they found that this happened in High Middle Ages, around 1000 A.D. Intriguingly these strong selection pressures coincided with increasing urbanization and Christian edicts that enforced fasting and the exclusion of four legged animals from the menu. Could Medieval religious rules have increased the demand for poultry and thereby altered chicken evolution?

"With our new method we see that the time of selection coincides with an increase in the amount of chicken bones in the archaeological records across Northern Europe. Intriguingly, they also coincide with several socio-cultural changes, including a general increase in the popularity of Christian beliefs, new religious dietary rules and increase in urbanization (favoring traits that mean that animals could be kept in small spaces). We cannot say which one of these was most important but most likely a combination of all these factors affected selective pressures on European chickens and consequently their evolution." Says author Anders Eriksson.

Scientists have been attempting to link traits that distinguish domesticated animals from their wild relatives to specific changes in their genomes. Recent studies of domestic chickens have pinpointed genetic variants in two genes: the thyroid-stimulating hormone receptor (TSHR) and the beta-carotene dioxygenase 2 (BCD02), both of which also show strong signals of selection. Having two copies of a form of the TSHR gene is thought to lead to a loss of seasonal reproduction in many domestic animals. In chickens, a variant of this gene has been shown to enable faster egg-laying, and result in reduced aggression and decreased fear of humans. BCD02 has an effect on skin pigmentation in birds, with one form associated with white or grey skin, and another associated with yellow skin in well-fed chickens.

In 2014, a group led by Greger Larson looked at these two genes in around 100 archaeological samples from Europe spanning the last 2,200 years. But due to a lack of the right statistical methods, they did not quantify the timing or strength of natural selection.

Now, a research team led by Liisa Loog, Anders Eriksson, Mark Thomas and Greger Larson analyzed ancient and modern chicken DNA using a statistical method they developed to pinpoint when selection starts and how strong it is. They found that selection on the TSHR gene began around 920 AD, which coincides with increased chicken consumption across the whole of Northern Europe, as seen in the archaeological record.

"Several independent archaeological studies have documented substantial increases in the frequency of chicken remains between the 9th and 12th centuries AD, as well as a shift towards the management of adult hens, presumably to increase egg production." said Mark Thomas, an author on the study. "Intriguingly, this is the period when selection on the TSHR variant most likely kicked off".

There are several socio-economic factors could have contributed to the rise in popularity of poultry, including religious edicts that prohibited meat consumption during fasting. Importantly, chickens and eggs were not restricted by these edicts, which may have led to an increase in selective pressures on THSR, allowing chickens to be raised in closer confines as demand for their meat and eggs increased.

"This significant intensification of chicken and egg production has been linked to Christian fasting practices, originating with the Benedictine Monastic Order, which disallowed the consumption of meat from four-legged animals during fasting periods, but the restrictions did not extend to birds or eggs. These dietary rules were adopted across Europe and applied to all segments of society around 1000 AD." said author Anders Eriksson. "However, The increase in chicken production could also have been favored by urbanization, the introduction of the more efficient agricultural practices and a warmer climate."

For BCDO2, the gene which plays a role in leg color, they authors show that while the genetic patterns are compatible with some level of selection, the genetics of modern chickens is best explained as a consequence of Victorian breeding practices, which involved cross-breeding native European breeds with exotic Asian chickens.

The authors new statistical approach, which combines mathematical modeling with ancient DNA information, provides a tool for exploring the links between genetic evolution in domestic plants and animals and the parallel cultural changes in human populations, as they have each responded to alterations in natural and artificial selective pressures.

"We tend to think that there were wild animals, and then there were domestic animals. We tend to discount how selection pressures on domestic plants and animals varied through time in response to different preferences or ecological factors. This study demonstrates just how easy it is to drive a trait to a high frequency in an evolutionary blink of an eye, and suggests that simply because a domestic trait is ubiquitous, it may not have been a target for selection at the very beginning of the domestication process", said author Greger Larson.

"The processes and driving mechanisms responsible for generating the patterns of genomic variation in humans and their co-dependent domestic plants and animals found today can be explored using this new tool" concluded first author Liisa Loog.

Explore further: Feral chickens spread light on evolution

More information: Liisa Loog et al, Inferring allele frequency trajectories from ancient DNA indicates that selection on a chicken gene coincided with changes in medieval husbandry practices, Molecular Biology and Evolution (2017). DOI: 10.1093/molbev/msx142

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Holy chickens: Did Medieval religious rules drive domestic chicken evolution? - Phys.Org

The scientists say the newly identified dinosaur,Vouivria,died at a young ageweighing around 15,000 kg (33,000 lb)

After sitting idly in a Paris history museum for more than 80 years, a previously overlooked fossil is shedding light on a decidedly obscure chapter in dinosaur evolution. Not only is the new species providing scientists with new clues, it has turned out to be the earliest relative of a certain long-necked plant-eater called the Brachiosaurus.

In 1934 paleontologists came across a dinosaur fossil in the village of Damparis in eastern France. A species was not immediately identified and the fossil was mostly ignored by scientific literature in the 30s and 40s, referred to only as the "Damparis dinosaur." But now scientists from Imperial College London, together with France's Museum National d'Histoire Naturelle, where Damparis has been stored, and Universit Paris 1 Panthon-Sorbonne, have pulled it out for another look.

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New analysis of the fossil has revealed it to be a brachiosaurid sauropod, a group belonging to a larger group of dinosaurs called the titanosauriforms. These were some of the biggest creatures to ever live on land and roamed the Earth from at least the Late Jurassic (around 160 million years ago) to the mass-extinction event at the end of the Cretaceous period (65 million years ago).

The researchers say that the age of the fossil, which has now been named Vouivria damparisensis, is around 160 million years old. This is significant for a couple of reasons. It makes it the earliest known fossil from the titanosauriform family and therefore the earliest relative of the brachiosaurus, and helps to fill in what was a sizable hole in the existing fossil records.

"Vouivria would have been a herbivore, eating all kinds of vegetation, such as ferns and conifers," says Imperial College London's Dr Philip Mannion, lead author of the study. "This creature lived in the Late Jurassic, around 160 million years ago, at a time when Europe was a series of islands. We don't know what this creature died from, but millions of years later it is providing important evidence to help us understand in more detail the evolution of brachiosaurid sauropods and a much bigger group of dinosaurs that they belonged to, called titanosauriforms."

The scientists say Vouivria died at a young age, weighing around 15,000 kg (33,000 lb) and measured more than 15 m long (50 ft), around 1.5 times the size of a double-decker bus in the UK. It had a long neck, a long tail and four legs of equal length.

Without many fossils to work with, it has been hard for scientists to plot the evolution of the titanosauriforms and their spread across the planet. But already Vouivria is starting to fill in some of the blanks. The team believes that the dinosaur died in a coastal lagoon in the midst of a short sea level decline in Europe, and was then buried when the sea rose again.

Working the new evidence into analysis of brachiosaurid evolution, the scientists now believe that the creatures were most likely extinct in Europe soon after this creature lived by the Early Cretaceous period and restricted to what is now Africa and the USA. They are now expanding that analysis to consider the evolutionary relationships between all members of the titanosauriform family to understand their evolution even further.

The research was published in the journal PeerJ.

Source: Imperial College London

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Forgotten fossil fills blanks in dinosaur evolution - New Atlas

The Scientist

Evolution's Quick Pace Affects Ecosystem Dynamics The Scientist Starting in the late 1970s, aspiring evolutionary biologist David Reznick became intent on documenting evolution in action. Although he had learned in school that observable change took place over millennia, the young biologist questioned that notion ...

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Evolution's Quick Pace Affects Ecosystem Dynamics - The Scientist