Giant impact caused difference between Moon's hemispheres

Moon.

The stark difference between the Moon's heavily-cratered farside and the lower-lying open basins of the Earth-facing nearside has puzzled scientists for decades.

Now, new evidence about the Moon's crust suggests the differences were caused by a wayward dwarf planet colliding with the Moon in the early history of the solar system. A report on the new research has been published in AGU's Journal of Geophysical Research: Planets.

The mystery of the Moon's two faces began in the Apollo era when the first views of its farside revealed the surprising differences. Measurements made by the Gravity Recovery and Interior Laboratory (GRAIL) mission in 2012 filled in more details about the structure of the Moon -- including how its crust is thicker and includes an extra layer of material on its farside.

There are a number of ideas that have been used to try and explain the Moon's asymmetry. One is that there were once two moons orbiting Earth and they merged in the very early days of the Moon's formation. Another idea is that a large body, perhaps a young dwarf planet, found itself in an orbit around the Sun that put it on a collision course with the Moon. This latter giant impact idea would have happened somewhat later than a merging-moons scenario and after the Moon had formed a solid crust, said Meng Hua Zhu of the Space Science Institute at Macau University of Science and Technology and lead author of the new study. Signs of such an impact should be visible in the structure of the lunar crust today.

"The detailed gravity data obtained by GRAIL has given new insight into the structure of the lunar crust underneath the surface," Zhu said.

The new findings from GRAIL gave Zhu's team of researchers a clearer target to aim for with the computer simulations they used to test different early-Moon impact scenarios. The study's authors ran 360 computer simulations of giant impacts with the Moon to find out whether such an event millions of years ago could reproduce the crust of today's Moon as detected by GRAIL.

They found the best fit for today's asymmetrical Moon is a large body, about 480 miles (780 kilometers) in diameter, smacking into the nearside of the Moon at 14,000 miles per hour (22,500 kilometers per hour). That would be the equivalent of an object a bit smaller than the dwarf planet Ceres moving at a speed about one-quarter as fast as the meteor pebbles and sand grains that burn up as "shooting stars" in Earth's atmosphere. Another good fit for the impact combinations the team modeled is a slightly smaller, 450-mile (720-kilometer) diameter, object hitting at a mildly faster 15,000 miles per hour (24,500 kilometers per hour).

Under both these scenarios, the model shows the impact would have thrown up vast amounts of material that would fall back on the Moon's surface, burying the primordial crust on the farside in 3 to 6 miles (5 to 10 kilometers) of debris. That is the added layer of crust detected on the farside by GRAIL, according to Zhu.

The new study suggests the impactor was not likely an early second moon of Earth's. Whatever the impactor was -- an asteroid or a dwarf planet -- it was probably on its own orbit around the Sun when it encountered the Moon, said Zhu.

The giant impact model also provides a good explanation for the unexplained differences in isotopes of potassium, phosphorus and rare-earth elements like tungsten-182 between the surfaces of the Earth and Moon, the researchers explain. These elements could have come from the giant impact, which would have added that material to the Moon after its formation, according to the study's authors.

"Our model can thus explain this isotope anomaly in the context of the giant impact scenario of the Moon's origin." the researchers write.

The new study not only suggests an answer to ongoing questions about the Moon, but may also provide insight into the structure of other asymmetrical worlds in our solar system like Mars wrote the researchers.

Read more at Science Daily

Research reveals insulin-producing beta cells may change function in diabetes

Diabetes concept.

A revolutionary new study using only materials derived from humans has revealed that insulin-producing beta cells can change their function in diabetes -- and that this change may be reversible.

Research led by the University of Exeter is the first to look at the cells using an entirely animal-free model, instead using a completely human cell system in laboratories for the first time. The team found that the RNA messaging system which tells proteins how to behave in cells is different in diabetes. The changes lead to some of the beta cells no longer producing insulin which regulates blood sugar, and instead producing somatostatin, which can block the the secretion of other important hormones including insulin itself.

The research is published in Human Molecular Genetics and funded by Animal Free Research UK. The study may give new insights into how high blood sugar can alter the behaviour of important hormone-producing cells, and pave the way to new treatments.

Professor Lorna Harries, of the University of Exeter Medical School, who led the research, said: "These insights are really exciting. Only recently, Exeter researchers discovered that people with type 1 diabetes still retain some insulin-producing cells, but the environment produced by diabetes can be toxic for these cells that remain. Our work could lead to new changes to protect these cells, which could help people maintain some ability to make their own insulin. The method we used of creating an all-human cell system for the first time is significant -- I don't think we'd have seen these changes in mouse cells."

Carla Owen, Chief Executive of Animal Free Research UK which funded the research, said: "This is pioneering research at its best -- we supported the Exeter team to create a novel method to investigate how diabetes affects humans, rather than animals. Their breakthrough findings would never have been discovered in animals, highlighting the importance of using a human-relevant approach to understanding human diseases. We're proud to be supporting the next phase to take this discovery forward and closer to treatments for people living with diabetes."

The team examined what happens to human beta cells when exposed to an environment that replicated type 2 diabetes.

Beta cell loss occurs in both type 1 and type 2 diabetes. Scientists have previously assumed this was because the microenvironment around the cells causes them to die.

However, the team found for the first time that a proportion of the cells are no longer beta cells that are making insulin. They had actually started to make a different hormone called somatostatin -- characteristic of a delta cell.

The team than analysed post mortem pancreas tissue from people with either type 1 or type 2 diabetes. This revealed that they have more delta cells than they should have, suggesting that diabetes might be causing some of the beta cells to turn into delta cells in people as well as in cells in the laboratory.

Similar findings have been reported in animal models, but the changes are different. In mice, most of the changes are beta to alpha cells, not delta cells. Alpha cells make a different hormone called glucagon. This means that the consequences of changes in cell type might be different between mice and humans.

In the next step, the team investigated why the cells might change from beta cells to delta cells, by looking at gene regulation. They looked at differences in the genes that make the decision as to which type of RNA message is made which helps cells to deal with their environment. In samples from the pancreas of people with type 2 diabetes, they found that about a quarter of genes show disruption to the expected pattern of messages made compared with samples from people with no diabetes. This indicates that the differences in the regulators translate to differences in messages made. The type of RNA message made controls every aspect of cell life or behaviour, and the authors speculate this could be why the treated cells behave differently.

Read more at Science Daily

A new way of diagnosing and treating disease -- without cutting skin

Laser light

University of British Columbia researchers have developed a specialized microscope that has the potential ability to both diagnose diseases that include skin cancer and perform incredibly precise surgery -- all without cutting skin.

The researchers describe the technology in a study published today in Science Advances.

"Our technology allows us to scan tissue quickly, and when we see a suspicious or abnormal cell structure, we can perform ultra-precise surgery and selectively treat the unwanted or diseased structure within the tissue -- without cutting into the skin," said Yimei Huang, co-lead author of the study and a former postdoctoral fellow at the department of dermatology and skin science at UBC and BC Cancer.

Huang co-led the study with Zhenguo Wu, a UBC PhD student.

The device is a specialized type of multiphoton excitation microscope that allows imaging of living tissue up to about one millimeter in depth using an ultrafast infrared laser beam. What sets the researchers' microscope apart from previous technology is that it's capable of not only digitally scanning living tissue, but also treating the tissue by intensifying the heat produced by the laser.

When applied to treating diseases of the skin, the microscope allows medical professionals to pinpoint the exact location of the abnormality, diagnose it and treat it instantly. It could be used to treat any structure of the body that is reached by light and that requires extremely precise treatment, including nerves or blood vessels in the skin, eye, brain or other vital structures.

"We can alter the pathway of blood vessels without impacting any of the surrounding vessels or tissues," said study co-author Harvey Lui, professor at the department of dermatology and skin science at UBC and the Vancouver Coastal Health Research Institute, and a dermatologist at BC Cancer. "For diagnosing and scanning diseases like skin cancer, this could be revolutionary."

The researchers wanted to make multiphoton microscope technology more versatile while also increasing its precision.

"We wanted to be able to identify what was happening under the skin from many different angles and to have the capability of imaging different body sites," said senior author Haishan Zeng, professor of dermatology, pathology and physics at UBC and distinguished scientist with BC Cancer.

"Once we achieved that, we wondered whether we could transform this diagnostic device into a treatment device by simply turning up the power of the laser."

The results were incredibly exciting.

"We are not only the first to achieve fast video-rate imaging that enables clinical applications, but also the first to develop this technology for therapeutic uses," said Zeng.

The researchers have partnered with several UBC departments, including mechanical engineering, electrical engineering and ophthalmology, to develop different versions of the technology. Exploration includes research into the development of a miniature version that could be used to perform microscopic examinations and treatment during endoscopy -- a non-surgical procedure used to examine a person's digestive tract using an endoscope, a flexible tube with a light and camera attached to it.

Read more at Science Daily

Jawless fish take a bite out of the blood-brain barrier

Lamprey mouth.

A jawless parasitic fish could help lead the way to more effective treatments for multiple brain ailments, including cancer, trauma and stroke.

One major challenge in treating cancers and other disorders of the brain is ensuring that medicines reach their targets. A team of biomedical engineers and clinician-scientists at the University of Wisconsin-Madison and the University of Texas at Austin borrowed molecules from the immune system of the parasitic sea lamprey to deliver anti-cancer drugs directly to brain tumors.

They published their results today (May 15, 2019) in the journal Science Advances.

Unlike most currently used medicines, which target specific features on or inside individual cells in our body's organs and tissues, the lamprey-derived molecules take aim at a different target -- the extracellular matrix, a tangled mesh of proteins and sugars that supports and surrounds all cells in the brain.

The researchers believe the molecules could be adapted and combined with a wide array of other therapies, offering hope to treat numerous brain ailments beyond tumors, such as multiple sclerosis, Alzheimer's disease or even traumatic injuries.

"This set of targeting molecules appears somewhat agnostic to the disease," says Eric Shusta, a professor of chemical and biological engineering at UW-Madison. "We believe it could be applied as a platform technology across multiple conditions."

The technology takes advantage of the fact that many diseases disrupt one of the body's natural defense mechanisms: the blood-brain barrier, which lines the blood vessels of the central nervous system and protects the brain from potential threats such as circulating toxins or pathogens.

Many drugs -- including the lamprey-derived molecules -- cannot reach targets in the brain when they are injected into the bloodstream, because the blood-brain barrier normally prevents large molecules from leaving the blood vessels in the brain.

Yet, in conditions such as brain cancer, stroke, trauma and multiple sclerosis, the barrier becomes leaky in and around the disease locations. A leaky barrier offers a unique point of entry. It will allow the matrix-targeting lamprey molecules to access the brain and deliver drugs precisely on target.

"Molecules like this normally couldn't ferry cargo into the brain, but anywhere there's a blood-brain barrier disruption, they can deliver drugs right to the site of pathology," says Shusta.

Knowing that brain tumors often cause the barrier to leak, the researchers linked the lamprey-derived molecules to a Food and Drug Administration-approved chemotherapy called doxorubicin. The treatment prolonged survival in mouse models of glioblastoma, the incurable brain cancer that afflicted Senators John McCain and Ted Kennedy.

The matrix-targeting strategy means a wide variety of therapies could be linked to the lamprey-derived molecules. They could also be combined with techniques that temporarily open the blood brain barrier at specific brain sites. And it's possible that drugs delivered to the matrix could accumulate to a much higher therapeutic dose than medicines aimed at the inside of cells.

"Similar to water soaking into a sponge, the lamprey molecules will potentially accumulate much more of the drug in the abundant matrix around cells compared to specific delivery to cells," says collaborator John Kuo, a neurosurgeon-scientist and professor of neurosurgery in the Dell Medical School at the University of Texas at Austin.

Additionally, brain cells actively pump out many chemicals -- a useful trick to protect against toxic compounds, but a major headache for achieving effective therapeutic doses for medicines.

Targeting the matrix that surrounds the cells sidesteps that pumping problem.

"This could be a way to hold therapies in place that don't otherwise accumulate well in the brain so they can be more effective," says Ben Umlauf, a postdoctoral scholar in Shusta's group who isolated the lamprey-derived molecules.

Lampreys and humans have similar immune systems. But instead of producing antibodies to neutralize threats (that's how vaccines help protect us against measles), they produce small crescent-shaped defensive molecules called VLRs. To obtain their drug-delivery molecules, the researchers "vaccinated" lampreys with components of the brain extracellular matrix and then hunted through many thousands of VLRs to find one that stuck specifically to the brain matrix.

Importantly, in the mouse studies, the lamprey-derived molecules circulated throughout the body without accumulating in healthy brain tissue or other organs. This targeted delivery is especially important in cancer treatments, since many therapies frequently cause debilitating adverse reactions due to indiscriminate effects on healthy cells.

In the future, the researchers plan to link the matrix-targeting molecules to additional anti-cancer drugs, such as immunotherapy agents that activate a patient's own immune system to destroy tumors.

They also see promise in using the molecules as diagnostic tools to detect blood-brain barrier disruption by linking the matrix binders with probes for advanced imaging with PET scanners or MRI machines.

And because the molecules appear to be quite adaptable, the researchers speculate that many other medicines for the brain could become more effective if they were targeted to the matrix.

"I'm excited about trying this strategy in different disease model systems," says Kuo. "There are several disease processes that disrupt the blood-brain barrier and we could conceive of delivering a variety of different therapies with these molecules."

Read more at Science Daily

Brain's insular cortex processes pain and drives learning from pain

Pain concept (touching cactus).

Acute pain, e.g. hitting your leg against a sharp object, causes an abrupt, unpleasant feeling. In this way, we learn from painful experiences to avoid future harmful situations. This is called "threat learning" and helps animals and humans to survive. But which part of the brain actually warns other parts of the brain of painful events so that threat learning can occur?

We've known for a while that a brain area called amygdala is important for threat learning. But now, scientists from the lab of Ralf Schneggenburger at EPFL have discovered that the insular cortex sends such "warnings." The insular cortex, folded deep within the lateral sulcus of the brain, is known to code for feelings about our own body. Moreover, neurons in the insular cortex connect to neurons in the amygdala, but the function of this brain connection was previously little studied.

The insular cortex being similar between mice and men, the scientists turned to mice for their study. The researchers used light-activated ion channels that were genetically engineered into specific neurons in the brains of mice. This allowed them to switch off the electrical activity of neurons in the insular cortex by shining brief pulses of laser-light during the threat-learning behavior.

By switching off the insular cortex during the painful event, the scientists found that mice became essentially fearless against a mild electric shock to the foot. In addition, the ability of the mice to learn from the painful event was greatly reduced.

The study demonstrates that, besides informing our brain about bodily states, the insular cortex can send a strong warning signal to other brain areas involved in forming a memory of the unpleasant event. "Because silencing the insular cortex takes away the unpleasant feeling normally associated with a painful event, our study suggests that neurons in the insular cortex cause the subjective feeling of pain, and induce learning about the pain in other brain areas," says Schneggenburger.

"Because of this, activity in the insular cortex could have powerful consequences on shaping brain connectivity in other brain areas, which fits with studies that show aberrant activity in the insular cortex in humans with certain psychiatric diseases. Thus, our study of the neuronal mechanisms of how pain is encoded in the brain -- together with future studies of the underlying plasticity mechanisms -- might be relevant for the development of treatments for psychiatric diseases such as anxiety and post-traumatic stress disorders."

From Science Daily

Scientists find new type of cell that helps tadpoles' tails regenerate

Tadpole.

Researchers at the University of Cambridge have uncovered a specialised population of skin cells that coordinate tail regeneration in frogs. These 'Regeneration-Organizing Cells' help to explain one of the great mysteries of nature and may offer clues about how this ability might be achieved in mammalian tissues.

It has long been known that some animals can regrow their tails following amputation -- Aristotle observed this in the fourth century B.C. -- but the mechanisms that support such regenerative potential remain poorly understood.

Using 'single-cell genomics', scientists at the Wellcome Trust/ Cancer Research UK Gurdon Institute at the University of Cambridge developed an ingenious strategy to uncover what happens in different tadpole cells when they regenerate their tails.

Recent Cambridge-led advances in next-generation sequencing mean that scientists can now track which genes are turned on (being expressed) throughout a whole organism or tissue, at the resolution of individual cells. This technique, known as 'single-cell genomics', makes it possible to distinguish between cell types in more detail based on their characteristic selection of active genes.

These breakthroughs are beginning to reveal a map of cellular identities and lineages, as well as the factors involved in controlling how cells choose between alternative pathways during embryo development to produce the range of cell types in adults.

Using this technology, Can Aztekin and Dr Tom Hiscock -- under the direction of Dr Jerome Jullien -- made a detailed analysis of cell types involved in regeneration after damage in African clawed frog tadpoles (Xenopus laevis). Details are published today in the journal Science.

Dr Tom Hiscock says: "Tadpoles can regenerate their tails throughout their life; but there is a two-day period at a precise stage in development where they lose this ability. We exploited this natural phenomenon to compare the cell types present in tadpoles capable of regeneration and those no longer capable."

The researchers found that the regenerative response of stem cells is orchestrated by a single sub-population of epidermal (skin) cells, which they termed Regeneration-Organizing Cells, or ROCs.

Can Aztekin says: "It's an astonishing process to watch unfold. After tail amputation, ROCs migrate from the body to the wound and secrete a cocktail of growth factors that coordinate the response of tissue precursor cells. These cells then work together to regenerate a tail of the right size, pattern and cell composition."

In mammals, many tissues such as the skin epidermis, the intestinal epithelium and the blood system, undergo constant turnover through life. Cell lost through exhaustion or damage are replenished by stem cells. However, these specialised cells are usually dedicated to tissue sub-lineages, while the ability to regenerate whole organs and tissues has been lost in all but a minority of tissues such as liver and skin.

Read more at Science Daily

Sedimentary, my dear Johnson: Is NASA looking at the wrong rocks for clues to Martian life?

Mars robotic rover illustration.

In 2020, NASA and European-Russian missions will look for evidence of past life on Mars. But while volcanic, igneous rock predominates on the Red Planet, virtually the entire Earth fossil record comes from sedimentary rocks.

Addressing the problem in Frontiers in Earth Science, Swedish scientists have begun compiling evidence of fossilized microbes in underexplored igneous rock environments on Earth, to help guide where to search for a Martian fossil record -- and what to look for.

"We propose a 'volcanic microfossil atlas' to help select target sites for missions seeking evidence of extraterrestrial life, such as the NASA Mars mission 2020 and ExoMars," says lead author Dr. Magnus Ivarsson. "The atlas could also help us recognize what Mars microfossils might look like, by identifying biosignatures associated with different types of fossilized microbes."

Earth's deep biosphere

Ivarsson and colleagues study life buried in deep rock and deep time: fossilized remains of mysterious microbes, that have lived up to a kilometer below the deepest ocean floors for as long as 3.5 billion years.

"The majority of the microorganisms on Earth are believed to exist in the deep biosphere of the ocean and continental crust," reveals Ivarsson. "Yet we are just now beginning to explore -- through deep drilling projects -- this hidden biosphere."

In a watery world that never sees sunlight, bacteria, fungi and other microbes have adapted to feed on the igneous rock that surrounds them -- or even on each other. They spread through micro-fractures and cavities, forming complex and extended communities.

"Upon death, the microbial communities become fossilized on the walls of their rocky home. These microfossils can provide a history of microbial life in volcanic rock."

A volcanic microfossil atlas

Crucially, Earth's oceanic crust is geochemically very similar to the volcanic rocks that dominate the Martian landscape.

"Our aim is to be able to use the oceanic crust microfossil record as a model system to guide Martian exploration," Ivarsson explains. "Our review of existing knowledge is an important first step, but a more comprehensive understanding of the deep life is needed to show where and what to search for."

To achieve this, says Ivarsson, we need to collect more data on microfossil appearance and location -- but also, on their chemical composition.

"These fossils often preserve immense morphological detail. For example, we can distinguish broad classes of fungi through the appearance of spores, fruiting bodies, mycelia and other growth states -- or of bacteria, through the presence of cauliflower-like formations, generations of biofilms preserved as laminated sheets, and other characteristic community structures.

"But analysis of lipids and carbon isotopes in microfossils will make it possible to discriminate more precise groups based on their metabolism.

"Altogether this information will help to identify which types of microorganism are most likely to have been preserved on Mars, and which geochemical conditions most favour fossilization."

A fossil record on Mars

The microfossil atlas would therefore also help to determine which samples should be targeted for return to Earth, given the limited payload of the Mars missions.

"Both NASA's Mars 2020 and the ExoMars missions are capable of detecting larger fossilized structures from volcanic rocks, such as mm-sized mineralized fungal mycelia, or larger microstromatolites in open vesicles.

Read more at Science Daily

Earliest evidence of the cooking and eating of starch

Fire in hearth.

New discoveries made at the Klasies River Cave in South Africa's southern Cape, where charred food remains from hearths were found, provide the first archaeological evidence that anatomically modern humans were roasting and eating plant starches, such as those from tubers and rhizomes, as early as 120,000 years ago.

The new research by an international team of archaeologists, published in the Journal of Human Evolution, provides archaeological evidence that has previously been lacking to support the hypothesis that the duplication of the starch digestion genes is an adaptive response to an increased starch diet.

"This is very exciting. The genetic and biological evidence previously suggested that early humans would have been eating starches, but this research had not been done before," says Lead author Cynthia Larbey of the Department of Archaeology at the University of Cambridge. The work is part of a systemic multidisciplinary investigation into the role that plants and fire played in the lives of Middle Stone Age communities.

The interdisciplinary team searched for and analysed undisturbed hearths at the Klasies River archaeological site.

"Our results showed that these small ashy hearths were used for cooking food and starchy roots and tubers were clearly part of their diet, from the earliest levels at around 120,000 years ago through to 65,000 years ago," says Larbey. "Despite changes in hunting strategies and stone tool technologies, they were still cooking roots and tubers."

Professor Sarah Wurz from the School of Geography, Archaeology and Environmental Studies at the University of the Witwatersrand in Johannesburg, South Africa (Wits University) and principal investigator of the site says the research shows that "early human beings followed a balanced diet and that they were ecological geniuses, able to exploit their environments intelligently for suitable foods and perhaps medicines."

By combining cooked roots and tubers as a staple with protein and fats from shellfish, fish, small and large fauna, these communities were able to optimally adapt to their environment, indicating great ecological intelligence as early as 120,000 years ago.

"Starch diet isn't something that happens when we started farming, but rather, is as old as humans themselves," says Larbey. Farming in Africa only started in the last 10,000 years of human existence.

Humans living in South Africa 120,000 years ago formed and lived in small bands.

"Evidence from Klasies River, where several human skull fragments and two maxillary fragments dating 120,000 years ago occur, show that humans living in that time period looked like modern humans of today. However, they were somewhat more robust," says Wurz.

Klasies River is a very famous early human occupation site on the Cape coast of South Africa excavated by Wurz, who, along with Susan Mentzer of the Senckenberg Institute and Eberhard Karls Universit?t Tübingen, investigated the small (c. 30cm in diameter) hearths.

Read more at Science Daily

Scientists propose rethinking 'endangered species' definition to save slow-breeding giants

Elephants.

Conservation decisions based on population counts may fail to protect large, slow-breeding animals from irrevocable decline, according to new research coinciding with Endangered Species Day.

"Critical thresholds in so-called vital rates -- such as mortality and fertility rates among males and females of various ages -- can signal an approaching population collapse long before numbers drop below a point of no return," says lead author Dr. Shermin de Silva, President & Founder of Asian elephant conservation charity Trunks & Leaves. "We propose that conservation efforts for Asian elephants and other slow-breeding megafauna be aimed at maintaining their 'demographic safe space': that is, the combination of key vital rates that supports a non-negative growth rate."

A mammoth insight

Published in Frontiers in Ecology and Evolution, the study suggests that a combination of key vital rates governing population growth is a better indicator of a species' viability than short-term trends in population size and distribution.

"History bears this out," argues de Silva. "Genomic studies of the last mammoths isolated on Wrangel Island -- between Russia and Alaska -- have shown that although they were able to persist for thousands of years beyond the extinction of mainland populations with just ~300 individuals, they had accumulated numerous genetic mutations that may have eventually contributed to their extinction."

In other words populations of megafauna can become biologically inviable long before they disappear, if pushed beyond their 'demographic safe space.'

Females and calves key to saving the Asian elephant

The group applied the 'demographic safe space' concept to the case of the Asian elephant.

"Asian elephants are classified as 'Endangered' under the IUCN Red List because populations are thought to have declined by at least 50% in less than a century," explains de Silva. "There are fewer than 50,000 wild Asian elephants living today."

Studies show that wild Asian elephants breed extremely slowly, the majority producing just one calf in six years or more. Using mathematical modeling, de Silva and colleagues found that near-optimal reproduction and high calf survival is necessary to maintain non-negative population growth in the face of even modestly increased mortality among adult female age classes.

The approach shows a clear conservation priority for Asian elephants, a species in which the vast majority is tuskless.

"Measures to enhance survival of calves, and particularly females, are key to saving the Asian elephant," emphasizes de Silva.

"But while the attention of the world has been focused on the ivory trade, for critically endangered Asian elephant populations the greatest threat is habitat loss -- followed by illegal trade in live animals and parts.

"Habitat loss can create something known as 'extinction debt' by slowing down birth rates and increasing mortality rates. For slow breeding long-lived species, even incremental changes make a big difference, but their longevity can obscure the risk of extinction."

A demographic safe space for all megafauna

Conservation efforts for other large, slow-breeding species -- such as giraffes, rhinos, Bactrian camels and eastern gorillas -- could also benefit from modelling the interaction between vital rates. Data for these species in the wild are a scarce yet urgent necessity, suggest the authors.

"Rather than rely on simple population counts or estimates of near-term extinction probability, we urge that conservation resources for slow-breeding megafauna also be invested in identifying demographic tipping points and how to maintain populations within their safe spaces.

Read more at Science Daily

Neanderthals and modern humans diverged at least 800,000 years ago, research on teeth shows

Neanderthal vs human skull

Neanderthals and modern humans diverged at least 800,000 years ago, substantially earlier than indicated by most DNA-based estimates, according to new research by a UCL academic.

The research, published in Science Advances, analysed dental evolutionary rates across different hominin species, focusing on early Neanderthals. It shows that the teeth of hominins from Sima de los Huesos, Spain -- ancestors of the Neanderthals -- diverged from the modern human lineage earlier than previously assumed.

Sima de los Huesos is a cave site in Atapuerca Mountains, Spain, where archaeologists have recovered fossils of almost 30 people. Previous studies date the site to around 430,000 years ago (Middle Pleistocene), making it one of the oldest and largest collections of human remains discovered to date.

Dr Aida Gomez-Robles (UCL Anthropology), said: "Any divergence time between Neanderthals and modern humans younger than 800,000 years ago would have entailed an unexpectedly fast dental evolution in the early Neanderthals from Sima de los Huesos."

"There are different factors that could potentially explain these results, including strong selection to change the teeth of these hominins or their isolation from other Neanderthals found in mainland Europe. However, the simplest explanation is that the divergence between Neanderthals and modern humans was older than 800,000 years. This would make the evolutionary rates of the early Neanderthals from Sima de los Huesos roughly comparable to those found in other species."

Modern humans share a common ancestor with Neanderthals, the extinct species that were our closest prehistoric relatives. However, the details on when and how they diverged are a matter of intense debate within the anthropological community.

Ancient DNA analyses have generally indicated that both lineages diverged around 300,000 to 500,000 years ago, which has strongly influenced the interpretation of the hominin fossil record.

This divergence time, however, is not compatible with the anatomical and genetic Neanderthal similarities observed in the hominins from Sima de los Huesos. The Sima fossils are considered likely Neanderthal ancestors based on both anatomical features and DNA analysis.

Dr Gomez-Robles said: "Sima de los Huesos hominins are characterised by very small posterior teeth (premolars and molars) that show multiple similarities with classic Neanderthals. It is likely that the small and Neanderthal-looking teeth of these hominins evolved from the larger and more primitive teeth present in the last common ancestor of Neanderthals and modern humans."

Dental shape has evolved at very similar rates across all hominin species, including those with very expanded and very reduced teeth. This new study examined the time at which Neanderthals and modern humans should have diverged to make the evolutionary rate of the early Neanderthals from Sima de los Huesos similar to those observed in other hominins.

The research used quantitative data to measure the evolution of dental shape across hominin species assuming different divergent times between Neanderthals and modern humans, and accounting for the uncertainty about the evolutionary relationships between different hominin species.

"The Sima people's teeth are very different from those that we would expect to find in their last common ancestral species with modern humans, suggesting that they evolved separately over a long period of time to develop such stark differences."

Read more at Science Daily