Early evolution of the Earth–Moon system with a fast-spinning Earth
Wisdom et al
The isotopic similarity of the Earth and Moon has motivated a recent investigation of the formation of the Moon with a fast-spinning Earth (Cuk, M., Stewart, S.T., . Science, doi:10.1126/science.1225542). Angular momentum was found to be drained from the system through a resonance between the Moon and Sun. They found a narrow range of parameters that gave results consistent with the current angular momentum of the Earth–Moon system. However, a tidal model was used that was described as approximating a constant Q tidal model, but it was not a constant Q model. Here we use a conventional constant Q tidal model to explore the process. We find that there is still a narrow range of parameters in which angular momentum is withdrawn from the system that corresponds roughly to the range found earlier, but the final angular momentum is too low to be consistent with the Earth–Moon system. Exploring a broader range of parameters we find a new phenomenon, not found in the earlier work, that extracts angular momentum from the Earth–Moon system over a broader range of parameters. The final angular momentum is more consistent with the actual angular momentum of the Earth–Moon system. We develop a simple model that exhibits the phenomenon.
Monday, May 25, 2015
Climate, dust, and fire across the Eocene-Oligocene transition, Patagonia
Selkin et al
The Eocene-Oligocene transition (EOT) is typically interpreted as a time of drastic global cooling and drying associated with massive growth of a glacial icecap in Antarctica and the shift to an "icehouse" climate. The effects of this transition on the terrestrial environments, floras, and faunas of the Southern Hemisphere, however, have been unclear. Here we document simultaneous changes in fire regime and plant community in Patagonia, Argentina. Decreases in the concentration of magnetite in loessites from the Eocene-Oligocene Vera Member of the Sarmiento Formation correlate with decreases in the fraction of burnt palm phytoliths as well as more consistently palm-dominated phytolith assemblages. Association of magnetite and burnt palm phytoliths suggests intense wildfires, which appear to have been suppressed for ∼200 k.y. shortly after the EOT. The disappearance of fire-related characteristics near the EOT is possible if changes in regional wind patterns—consistent with observed changes in sediment particle sizes—caused changes in seasonal precipitation. These results imply a more important role for fire in structuring Eocene-Oligocene landscapes than previously thought.
Oldest Pathology in a Tetrapod Bone Illuminates the Origin of Terrestrial Vertebrates
Bishop et al
The origin of terrestrial tetrapods was a key event in vertebrate evolution, yet how and when it occurred remains obscure, due to scarce fossil evidence. Here, we show that the study of palaeopathologies, such as broken and healed bones, can help elucidate poorly understood behavioural transitions such as this. Using high-resolution finite element analysis, we demonstrate that the oldest known broken tetrapod bone, a radius of the primitive stem tetrapod Ossinodus pueri from the mid-Viséan (333 million years ago) of Australia, fractured under a high-force, impact-type loading scenario. The nature of the fracture suggests that it most plausibly occurred during a fall on land. Augmenting this are new osteological observations, including a preferred directionality to the trabecular architecture of cancellous bone. Together, these results suggest that Ossinodus, one of the first large (>2m length) tetrapods, spent a significant proportion of its life on land. Our findings have important implications for understanding the temporal, biogeographical and physiological contexts under which terrestriality in vertebrates evolved. They push the date for the origin of terrestrial tetrapods further back into the Carboniferous by at least two million years. Moreover, they raise the possibility that terrestriality in vertebrates first evolved in large tetrapods in Gondwana rather than in small European forms, warranting a re-evaluation of this important evolutionary event.
Also with the evolution of tetrapods lecture from the Royal Tyrrell Museum's Lecture Series, some of the earliest tetrapods known, like Ichthyostega and Acanthostega, were secondarily aquatic...meaning, yes, they returned to the water, this makes for some interesting implications.
Sunday, May 24, 2015
For a full decade, Gudmundur Olafsson was unable to move his right ankle. That's because it wasn't there. Olafsson's amputated lower leg was the delayed casualty of an accident from his childhood in Iceland, when he was hit by an oil truck. “I lived in pain for 28 years,” says Olafsson. “After 50-plus operations, I had it off.” For years after the operation he wore a Proprio Foot, a prosthetic with a motorized, battery-powered ankle, sold by the Reykjavik-based company Ossur. The Proprio is essentially a wearable robot, with algorithms and sensors that automatically adjust the angle of the foot during different points in its wearer's stride. Olafsson's ankle moved on autopilot.
But 14 months ago Ossur upgraded his hardware. Now, at age 48, Olafsson can move his right ankle by thinking about it. When the electrical impulse from his brain reaches the base of his leg, a pair of sensors embedded in his muscle tissue connect the neural dots, and wirelessly transmit that signal to the Proprio Foot. Since the command reaches the foot before the wearer's residual muscles actually contract, there's no unnatural lag between intention and action. That makes Olafsson part of a highly exclusive club. Along with David Ingvasson, a fellow Ossur tester, he's one of the only people on the planet who owns a brain-controlled bionic limb. Ossur unveiled its implanted myoelectric sensor (IMES) technology today at an event in Copenhagen, and is now preparing large-scale clinical trials, in the hopes of reaching the market in three to five years.
“The first time, to be honest, I started to cry."
This is a bigger breakthrough in the field of robotics and advanced prosthetics than it might appear. Brain-controlled bionic limbs make headlines on a regular basis, with the implication that the science has been solved, and experimental systems are already transitioning to products. But most of those devices are confined to laboratories, and many require complex surgery, such as transplanting muscle tissue or implanting electrodes in a subject's brain. These devices look like the real thing in brief, sometimes compelling video clips. But so far, prosthetics that respond to thoughts are not so much a reality as a promise.
To Erik Trinkaus, the jaw of the oldest modern human found in Europe has always looked strange. Its huge wisdom teeth and hefty, buttressed lower jaw reminded him of Neandertals, and he argued that this fossil, 37,000 to 42,000 years old, was the product of generations of mixing between modern humans and our extinct cousins. “It wasn't a popular idea,” admits Trinkaus, a paleoanthropologist at Washington University in St. Louis. Other paleoanthropologists insisted that the young man whose remains were found in 2002 in Peştera cu Oase cave in Romania was just a chunky example of our own species.
Now, 15 years later, Trinkaus has been vindicated by ancient DNA. The young Oase man inherited as much as one-tenth of his DNA from a Neandertal ancestor, and that ancestor lived only 200 years or so previously, according to a talk this month at Cold Spring Harbor Laboratory in New York. “One of Oase's ancestors—its great-great-great-grandparent—is Neandertal,” reported Qiaomei Fu, a geneticist at the Chinese Academy of Sciences–Max Planck Society Joint Laboratory for Human Evolution in Beijing and a postdoc in the lab of population geneticist David Reich at Harvard Medical School. The finding is “important as the first direct evidence of a very recent admixture event in Europe,” says population geneticist Laurent Excoffier of the University of Bern.
Europe just after the arrival of modern humans has long seemed a likely setting for such close encounters, given that Neandertals and modern humans overlapped there about 45,000 to 39,000 years ago. But until now, ancient DNA pointed to a different time and place for such a liaison. By sequencing the genomes of fossil Neandertals and comparing them with today's human genomes, paleogeneticists had found that living Europeans and Asians—but not Africans—have inherited just 1% to 4% of their DNA from Neandertals. DNA from fossils of two modern humans from what is now Russia also suggested that their Neandertal heritage was faint (see http://scim.ag/RussDNA). So researchers proposed that modern humans and Neandertals had rare and relatively early encounters, perhaps in the Middle East, when moderns swept out of Africa 60,000 to 50,000 years ago.
The DNA from Oase 1, a lower jaw without a skull, complicates that picture, Fu reported at the Biology of Genomes meeting. Working in a team led by paleogeneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, she and her colleagues captured 2.2 million base pairs of the fossil's DNA. Then, they sequenced 78,055 locations where the genomes of Neandertals and modern humans are known to differ. They found that the Oase man had far more Neandertal DNA—composing 4.8% to 11.3% of his genome—than either the ancient modern humans from Russia or living Europeans and Asians, Fu said.
What's more, the young man had inherited the Neandertal DNA in “large chunks,” including several segments more than 50 million base pairs long; one chunk spanned half the length of chromosome 12. Those unbroken stretches of Neandertal DNA suggest that the interbreeding must have been just four to six generations back. If the mixing had been more ancient, the long DNA segments would have been broken up by the reshuffling of chromosomes that takes place every generation. “This is quite amazing,” Fu said in her talk. “We're quite excited about that.”
If modern humans and Neandertals had several successful matings, why do living humans' genomes record only the earlier event?
Saturday, May 23, 2015
A large-scale anomaly in Enceladus’ microwave emission
Ries et al
The Cassini spacecraft flew by Enceladus on 6 November 2011, configured to acquire synthetic aperture RADAR imaging of most of the surface with the RADAR instrument. The pass also recorded microwave thermal emission from most of the surface. We report on global patterns of thermal emission at 2.17 cm based on this data set in the context of additional unresolved data both from the ground and from Cassini.
The observed thermal emission is consistent with dielectric constants of pure water or methane ice, but cannot discriminate between the two. The emissivity is similar to those of other icy satellites (≈≈0.7), consistent with volume scattering. The most intriguing result, however, is an anomaly in the thermal emission of Enceladus’ leading hemisphere. Evidence presented here suggests the anomaly is buried at depths on the order of a few meters. This anomaly is located in similar geographic location to anomalies previously detected with the CIRS and ISS instruments on Mimas, Tethys, and Dione (Howett, C.J.A. et al. . Icarus 216, 221–226; Howett, C.J.A. et al. . Icarus 221, 1084–1088; Howett, C.J.A. et al. . Icarus 241, 239–247; Schenk, P. et al. . Icarus 211, 740–757), but also corresponds with a geological feature on Enceladus’ leading terrain (Crow-Willard, E., Pappalardo, R.T. . Global geological mapping of Enceladus. In: EPSC-DPS Joint Meeting 2011. p. 635). Simple models show that the Crow-Willard and Pappalardo (Crow-Willard, E., Pappalardo, R.T. . Global geological mapping of Enceladus. In: EPSC-DPS Joint Meeting 2011. p. 635) model is a better fit to the data. Our best-supported hypothesis is that the leading hemisphere smooth terrain is young enough (<75 13="" 2="" a="" albedo="" an="" and="" anomaly="" at="" blockquote="" but="" cm.="" cm="" consistent="" depth="" electromagnetic="" gardening="" ground="" impact="" in="" increase="" is="" m="" measurements="" micrometeorite="" myr="" no="" observations="" of="" old="" picture="" radar="" region="" shallower="" show="" skin="" space="" than="" that="" the="" variation="" which="" with="">75>
Neural prosthetic devices implanted in the brain's movement center, the motor cortex, can allow patients with amputations or paralysis to control the movement of a robotic limb -- one that can be either connected to or separate from the patient's own limb. However, current neuroprosthetics produce motion that is delayed and jerky -- not the smooth and seemingly automatic gestures associated with natural movement. Now, by implanting neuroprosthetics in a part of the brain that controls not the movement directly but rather our intent to move, Caltech researchers have developed a way to produce more natural and fluid motions.
In a clinical trial, the Caltech team and colleagues from Keck Medicine of USC have successfully implanted just such a device in a patient with quadriplegia, giving him the ability to perform a fluid hand-shaking gesture and even play "rock, paper, scissors" using a separate robotic arm.
The results of the trial, led by principal investigator Richard Andersen, the James G. Boswell Professor of Neuroscience, and including Caltech lab members Tyson Aflalo, Spencer Kellis, Christian Klaes, Brian Lee, Ying Shi and Kelsie Pejsa, are published in the May 22 edition of the journal Science.
"When you move your arm, you really don't think about which muscles to activate and the details of the movement -- such as lift the arm, extend the arm, grasp the cup, close the hand around the cup, and so on. Instead, you think about the goal of the movement. For example, 'I want to pick up that cup of water,'" Andersen says. "So in this trial, we were successfully able to decode these actual intents, by asking the subject to simply imagine the movement as a whole, rather than breaking it down into a myriad components."
3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya
Harmand et al
Human evolutionary scholars have long supposed that the earliest stone tools were made by the genus Homo and that this technological development was directly linked to climate change and the spread of savannah grasslands. New fieldwork in West Turkana, Kenya, has identified evidence of much earlier hominin technological behaviour. We report the discovery of Lomekwi 3, a 3.3-million-year-old archaeological site where in situ stone artefacts occur in spatiotemporal association with Pliocene hominin fossils in a wooded palaeoenvironment. The Lomekwi 3 knappers, with a developing understanding of stone’s fracture properties, combined core reduction with battering activities. Given the implications of the Lomekwi 3 assemblage for models aiming to converge environmental change, hominin evolution and technological origins, we propose for it the name ‘Lomekwian’, which predates the Oldowan by 700,000 years and marks a new beginning to the known archaeological record.
Friday, May 22, 2015
Researchers at the University of California, Berkeley, have developed algorithms that enable robots to learn motor tasks through trial and error using a process that more closely approximates the way humans learn, marking a major milestone in the field of artificial intelligence.
They demonstrated their technique, a type of reinforcement learning, by having a robot complete various tasks -- putting a clothes hanger on a rack, assembling a toy plane, screwing a cap on a water bottle, and more -- without pre-programmed details about its surroundings.
"What we're reporting on here is a new approach to empowering a robot to learn," said Professor Pieter Abbeel in UC Berkeley's Department of Electrical Engineering and Computer Sciences. "The key is that when a robot is faced with something new, we won't have to reprogram it. The exact same software, which encodes how the robot can learn, was used to allow the robot to learn all the different tasks we gave it."
Robopoclypse now. ;)
Think it’s hard to find a place to charge your smartphone at the airport? Try finding a power outlet in the ocean.
Imagine you’re a robotic Navy mini-sub whose batteries are running low after a long mission monitoring, say, traffic around Chinese artificial islands in the South Pacific. Currently, you’d have to recharge at a land base or a surface ship. The former keeps you close to friendly shores while the latter gives away your presence. But if Navy program manager Mike Wardlaw makes it work, sometime in the early 2020s the Navy will start deploying unmanned, underwater pods where robots can recharge undetected — and securely upload the intelligence they’ve gathered to Navy networks.
Sec Mabus states UCLASS is a stepping stone to an unmanned fight and ought to be focused on ISR:
Ray Mabus likes robots. The Navy Secretary has declared the F-35 will be “the last manned strike fighter” the service ever buys and invested heavily in unmanned aircraft, boats, and submersibles. But Mabus has frustrated drone advocates on one major program: the Unmanned Carrier-Launched Surveillance and Strike (UCLASS) aircraft.
This morning, Mabus defended the Navy’s plans for a relatively modest UCLASS optimized for the “surveillance” aspect of its mission rather than the “strike” part — but he also promised UCLASS would be “the bridge” to a future unmanned strike plane, the one that replaces F-35. Given that the F-35 will be around for decades, however, this two-stage approach is unlikely to satisfy UCLASS critics like Senate ARmed Services chairman John McCain, House Seapower chairman Rep. Randy Forbes, and key players in the Pentagon itself, all of whom want a strike drone ASAP to deal with China.
Mabus said today at a DefenseOne leadership breakfast that “I’m for a full-up penetrating strike fighter” — eventually. “We see UCLASS as getting to that,” he said — but, he made clear, not as being that.
“For UCLASS…we ought to have endurance, we ought to have range, we ought to have payload,” he said, notably omitting stealth. “It should be an ISR [intelligence, surveillance, and reconnaissance] platform, it should be a refueling platform, but it also should be a strike platform [for] uncontested or minimally contested environments.”
In the longer term, he said, “it ought to be the bridge to a full-up strike fighter — an autonomous strike fighter — that [operates] in contested environments.”
Senator Forbes replies:
“Building ‘bridges’ sounds great, but at some point you need to cross them,” Rep. Forbes snapped in an email when I asked about Mabus’s comments. “While I understand the Navy’s desire to ‘crawl, walk, and run,’ I am concerned that in the race between anti-access and power projection capabilities, we are falling further and further behind. The carrier air wing is going to need a long-range, deep penetrating strike asset, and it is going to need it soon. Given that the UCLASS program is supposed to deliver its first operational aircraft to the fleet in 2022-23, I am concerned that the program seems to be driven by the needs of today and not those of tomorrow.”
The Sikorsky S-97 Raider hit an important milestone Friday with the successful first flight of its experimental rotorcraft.
The S-97, with two pilots, took off at the company's West Palm Beach, Fla., facility about 7 a.m. and performed all of its proscribed movements over roughly an hour. The flight test took on the basics — three take-offs and landings, and all cardinal movements at 10 knots — before more advanced tests over the year.
"This was, we feel, a really spectacular day for Sikorsky and aviation in general," said Mark Miller, Sikorsky's vice president for research and engineering. "It's not every day you have a first flight, and when you add on top of that a very differentiated, new and compelling product like the S-97 Raider, it makes it even more special.
"We're very excited, it was everything we wanted it to be and more, and it's the start of a new generation of helicopters and capabilities that we're really excited about," Miller said.
With the platform, Sikorsky officials said the company was firmly planting its flag for the Army's future vertical lift - light concept and armed aerial scout requirement. The S-97 was envisioned at one point as a contender replacement for the US Army's OH-58 Kiowa Scout, but the Army changed plans and scuttled the armed aerial scout for budgetary reasons, using the AH-64 Apache on an interim basis.
breaking my rules today...
The original snake ancestor was a nocturnal, stealth-hunting predator that had tiny hindlimbs with ankles and toes, according to research published in the open access journal BMC Evolutionary Biology.
The study, led by Yale University, USA, analyzed fossils, genes, and anatomy from 73 snake and lizard species, and suggests that snakes first evolved on land, not in the sea, which contributes to a longstanding debate. They most likely originated in the warm, forested ecosystems of the Southern Hemisphere around 128 million years ago.
Snakes show incredible diversity, with over 3,400 living species found in a wide range of habitats, such as land, water and in trees. But little is known about where and when they evolved, and how their original ancestor looked and behaved.
Lead author Allison Hsiang said: "While snake origins have been debated for a long time, this is the first time these hypotheses have been tested thoroughly using cutting-edge methods. By analyzing the genes, fossils and anatomy of 73 different snake and lizard species, both living and extinct, we've managed to generate the first comprehensive reconstruction of what the ancestral snake was like."
By identifying similarities and differences between species, the team constructed a large family tree and illustrated the major characteristics that have played out throughout snake evolutionary history.
Their results suggest that snakes originated on land, rather than in water, during the middle Early Cretaceous period (around 128.5 million years ago), and most likely came from the ancient supercontinent of Laurasia. This period coincides with the rapid appearance of many species of mammals and birds on Earth.
The ancestral snake likely possessed a pair of tiny hindlimbs, and targeted soft-bodied vertebrate and invertebrate prey that were relatively large in size compared to prey targeted by lizards at the time. While the snake was not limited to eating very small animals, it had not yet developed the ability to manipulate prey much larger than itself by using constriction as a form of attack, as seen in modern Boa constrictors.
While many ancestral reptiles were most active during the daytime (diurnal), the ancestral snake is thought to have been nocturnal. Diurnal habits later returned around 50-45 million years ago with the appearance of Colubroidea - the family of snakes that now make up over 85% of living snake species. As colder night time temperatures may have limited nocturnal activity, the researchers say that the success of Colubroidea may have been facilitated by the return of these diurnal habits.
ACADEMIC BUN FIGHT! Potential PaleoArchean Trace Fossils Mimic Biogenic Cenozoic Microbial Corrosion
Paleoarchean trace fossils in altered volcanic glass
Staudigel et al
Microbial corrosion textures in volcanic glass from Cenozoic seafloor basalts and the corresponding titanite replacement microtextures in metamorphosed Paleoarchean pillow lavas have been interpreted as evidence for a deep biosphere dating back in time through the earliest periods of preserved life on earth. This interpretation has been recently challenged for Paleoarchean titanite replacement textures based on textural and geochronological data from pillow lavas in the Hooggenoeg Complex of the Barberton Greenstone Belt in South Africa. We use this controversy to explore the strengths and weaknesses of arguments made in support or rejection of the biogenicity interpretation of bioalteration trace fossils in Cenozoic basalt glasses and their putative equivalents in Paleoarchean greenstones. Our analysis suggests that biogenicity cannot be taken for granted for all titanite-based textures in metamorphosed basalt glass, but a cautious and critical evaluation of evidence suggests that biogenicity remains the most likely interpretation for previously described titanite microtextures in Paleoarchean pillow lavas.
But are disputed!
Questioning the biogenicity of titanite mineral trace fossils in Archean pillow lavas
Grosch et al
Staudigel et al. (1) compare early Archean titanite microtextures to recent microtubules in Cenozoic volcanic seafloor glass to support a biogenic origin. However, given the 3.5 billion years of Earth history since eruption of the Archean lavas, many geological processes have affected these rocks, complicating the simple case for trace fossils. Using hollow and partially mineralized microtextures in modern seafloor basalt as an analog for argued microbial alteration of Archean glass is, in our opinion, a weak line of argument and an overextrapolated interpretation in support of biogenicity. The many assumptions required in their proposed bioalteration model are not supported by microbiological experiments or geological observations. For example, Staudigel et al. (1) require that hollow microbial tunnels are filled in by some process forming titanite, but when and how this occurs is not substantiated. The authors also contradict earlier work by abandoning organic carbon linings to the microtextures as evidence in support of biogenicity. Staudigel et al. provide no new data to support a biogenic origin, and we highlight that they have further complicated their lines of argument.
And then the original authors counter!
Reply to Grosch and McLoughlin: Glass bioalteration trace fossils can be preserved by titanite in Paleoarchean greenstones
Staudigel et al
Before debating the criticism that Grosch and McLoughlin (1) extend toward our paper (2), we point out that we agree on important issues, such as the difficulty of interpreting titanite textures in greenstones with complex metamorphic histories. We further agree with them that their images are too ambiguous to be certain of the presence of any biotextures.
We welcome Grosch and McLoughlin’s (1) clarification of their textural continuum of titanite textures in figure 1 of ref. 1, even though we are missing a genetic interpretation. We distinguish two types of titanite textures: (i) well-crystallized blade-like titanite crystals that have no resemblance to Cenozoic glass bioalteration and (ii) some “filamentous” textures that indeed closely resemble candidate biotextures. Lumping two visually distinct texture types into one group does not automatically give license to infer one process for their formation. Furthermore, we suggest here that none of the images conjure any simple metamorphic or biotic interpretations. In particular the candidate biotextures lack any obvious connections to glass surfaces or cracks in the glass, prohibiting a direct morphological comparison with Cenozoic biotextures.
Thursday, May 21, 2015
The J-20 combat aircraft, a new generation of combat aircraft, is currently engaged in intensive trial flights. According to photos circulating online, a newly designed J-20 coded 2013 carried out a series of low altitude maneuvers that demonstrated its relatively advanced performance.
Concerning the question of when the aircraft will be on active service, military expert Song Xinzhi said in a Beijing Television broadcast that J-20 is still using an prototype engine and it would be optimistic to expect it to come into service within one or two years.
From the photo we can clearly see features of the nose including the radome layout, the cockpit, and the canards.
An online report from Russia indicated that the maiden flight of the first prototype was made in January 2011, that China has already tested the sixth prototype of J-20, and that the J-20 at its initial stage is already an aircraft carrier killer.
According to the report, it takes five to six years for a new fighter to enter service. Therefore, it is very likely that this fighter will be equipped with a full set of avionics and arms in 2017.
Could the J-20 be operational within two years? Song Xinzhi points out that J-20 is still using a prototype engine which can only meet the demands of trial flights. A better engine is needed to unleash its full performance potential.
Machine learning can pinpoint rodent species that harbor diseases and geographic hotspots vulnerable to new parasites and pathogens. So reports a new study in the Proceedings of the National Academy of Sciences led by Barbara A. Han, a disease ecologist at the Cary Institute of Ecosystem Studies.
Most emerging infectious diseases are transmitted from animals to humans, with more than a billion people suffering annually. Safeguarding public health requires effective surveillance tools.
Han comments: "Historically, emerging infectious diseases have been dealt with reactively, with efforts focused on containing outbreaks after they've spread. We were interested in how machine learning could inform early warning surveillance by revealing the distribution of rodent species that are effective disease reservoirs."
Reappraisal of hydrocarbon biomarkers in Archean rocks
French et al
Hopanes and steranes found in Archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes, but the syngeneity of these hydrocarbon biomarkers is controversial. To resolve this debate, we performed a multilaboratory study of new cores from the Pilbara Craton, Australia, that were drilled and sampled using unprecedented hydrocarbon-clean protocols. Hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit, but when they were detectable, they had total hopane (less than 37.9 pg per gram of rock) and total sterane (less than 32.9 pg per gram of rock) concentrations comparable to those measured in blanks and negative control samples. In contrast, hopanes and steranes measured in the exteriors of conventionally drilled and curated rocks of stratigraphic equivalence reach concentrations of 389.5 pg per gram of rock and 1,039 pg per gram of rock, respectively. Polycyclic aromatic hydrocarbons and diamondoids, which exceed blank concentrations, exhibit individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1,000 ng per gram of rock in hydropyrolysates from the ultraclean cores. These results demonstrate that previously studied Archean samples host mixtures of biomarker contaminants and indigenous overmature hydrocarbons. Therefore, existing lipid biomarker evidence cannot be invoked to support the emergence of oxygenic photosynthesis and eukaryotes by ∼2.7 billion years ago. Although suitable Proterozoic rocks exist, no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation, so future exploration for Archean biomarkers should screen for rocks with milder thermal histories.
Wednesday, May 20, 2015
A systematic revision of Proconsul with the description of a new genus of early Miocene hominoid
McNulty et al
For more than 80 years, Proconsul has held a pivotal position in interpretations of catarrhine evolution and hominoid diversification in East Africa. The majority of what we ‘know’ about Proconsul, however, derives from abundant younger fossils found at the Kisingiri localities on Rusinga and Mfangano Islands rather than from the smaller samples found at Koru—the locality of the type species, Proconsul africanus—and other Tinderet deposits. One outcome of this is seen in recent attempts to expand the genus “Ugandapithecus” (considered here a junior subjective synonym of Proconsul), wherein much of the Tinderet sample was referred to that genus based primarily on differentiating it from the Kisingiri specimens rather than from the type species, P. africanus. This and other recent taxonomic revisions to Proconsul prompted us to undertake a systematic review of dentognathic specimens attributed to this taxon. Results of our study underscore and extend the substantive distinction of Tinderet and Ugandan Proconsul (i.e., Proconsul sensu stricto) from the Kisingiri fossils, the latter recognized here as a new genus. Specimens of the new genus are readily distinguished from Proconsul sensu stricto by morphology preserved in the P. africanus holotype, but also in I1s, lower incisors, upper and lower canines, and especially mandibular characteristics. A number of these differences are more advanced among Kisingiri specimens in the direction of crown hominoids. Proconsul sensu stricto is characterized by a suite of unique features that strongly unite the included species as a clade. There have been decades of contentious debate over the phylogenetic placement of Proconsul (sensu lato), due in part to there being a mixture of primitive and more advanced morphology within the single genus. By recognizing two distinct clades that, in large part, segregate these character states, we believe that better phylogenetic resolution can be achieved.
New material of Pseudoloris parvulus (Microchoerinae, Omomyidae, Primates) from the Late Eocene of Sossís (northeastern Spain) and its implications for the evolution of Pseudoloris
Minwer-Barakat et al
The species Pseudoloris parvulus, identified in several Middle and Late Eocene European sites, was previously known in the Iberian Peninsula by a single mandible preserving P4–M3 from Sossís (Southern Pyrenean Basins, northeastern Spain), described in the 1960s. Further field work at this Late Eocene site has led to the recovery of a large number of mammal remains, including the additional material of P. parvulus described in this paper. Some specimens of P. parvulus from this locality have also been recently found in the collections of the Naturhistorisches Museum Basel, Switzerland. The whole sample consists of 11 mandible fragments including several teeth, three upper dental series and nearly 80 isolated teeth including all of the dental elements, and represents the most complete sample of the genus described from the Iberian Peninsula. This abundant material allows us to provide an emended diagnosis for the species and to observe several directional changes in the dental morphology of the lineage including the species Pseudoloris saalae, Pseudoloris isabenae, Pseudoloris pyrenaicus and P. parvulus. These directional changes include the progressive reduction of the paraconid in the lower molars and the increase in size of the hypocone, metaconule and paraconule in the upper molars. Moreover, despite the overall resemblance among all of the samples ascribed to P. parvulus, we also recognize some differences, particularly an increase in size and better development of the hypocone from the oldest populations of the species, such as Le Bretou, to the most recent ones, like Sossís and Perrière. Therefore, this study sheds new light on the evolution of this genus, which inhabited Europe from the Middle Eocene to the Early Oligocene.
Paleomagnetic study on mid-Paleoproterozoic rocks from the Rio de la Plata craton: Implications for Atlantica
Rapalini et al
The first successful paleomagnetic study on middle Paleoproterozoic rocks from the Rio de la Plata craton is reported. Samples collected from the Soca and Isla Mala granitic bodies, located in southern Uruguay, provided characteristic remanences that were used to compute the first paleomagnetic poles for the craton for ca. 2.05–2.02 Ga. The poles were complemented by a virtual geomagnetic pole from the slightly older Marincho and Mahoma complexes. The paleomagnetic results suggest fast apparent polar wander at high paleolatitudes for the Rio de la Plata craton. Comparison with coeval poles from the Guiana, Congo–São Francisco and West African cratons indicates that a configuration of Atlantica that resembles their Western Gondwana fit is not supported by paleomagnetic data. The geologic similarities in these four cratons are supportive of a major crustal forming event between 2.2–2.0 Ga. A modified configuration for Atlantica is proposed that is consistent with our new (and older) paleomagnetic data. Atlantica was assembled at 2.1–2.05 Ga at polar latitudes and drifted towards the equator soon afterwards.
Tuesday, May 19, 2015
Quantitative inferences on the locomotor behaviour of extinct species applied to Simocyon batalleri (Ailuridae, Late Miocene, Spain)
Fabre et al
Inferences of function and ecology in extinct taxa have long been a subject of interest because it is fundamental to understand the evolutionary history of species. In this study, we use a quantitative approach to investigate the locomotor behaviour of Simocyon batalleri, a key taxon related to the ailurid family. To do so, we use 3D surface geometric morphometric approaches on the three long bones of the forelimb of an extant reference sample. Next, we test the locomotor strategy of S. batalleri using a leave-one-out cross-validated linear discriminant analysis. Our results show that S. batalleri is included in the morphospace of the living species of musteloids. However, each bone of the forelimb appears to show a different functional signal suggesting that inferring the lifestyle or locomotor behaviour of fossils can be difficult and dependent on the bone investigated. This highlights the importance of studying, where possible, a maximum of skeletal elements to be able to make robust inferences on the lifestyle of extinct species. Finally, our results suggest that S. batalleri may be more arboreal than previously suggested.
The two-domain tree of life is linked to a new root for the Archaea
Raymann et al
One of the most fundamental questions in evolutionary biology is the origin of the lineage leading to eukaryotes. Recent phylogenomic analyses have indicated an emergence of eukaryotes from within the radiation of modern Archaea and specifically from a group comprising Thaumarchaeota/“Aigarchaeota” (candidate phylum)/Crenarchaeota/Korarchaeota (TACK). Despite their major implications, these studies were all based on the reconstruction of universal trees and left the exact placement of eukaryotes with respect to the TACK lineage unclear. Here we have applied an original two-step approach that involves the separate analysis of markers shared between Archaea and eukaryotes and between Archaea and Bacteria. This strategy allowed us to use a larger number of markers and greater taxonomic coverage, obtain high-quality alignments, and alleviate tree reconstruction artifacts potentially introduced when analyzing the three domains simultaneously. Our results robustly indicate a sister relationship of eukaryotes with the TACK superphylum that is strongly associated with a distinct root of the Archaea that lies within the Euryarchaeota, challenging the traditional topology of the archaeal tree. Therefore, if we are to embrace an archaeal origin for eukaryotes, our view of the evolution of the third domain of life will have to be profoundly reconsidered, as will many areas of investigation aimed at inferring ancestral characteristics of early life and Earth.