Development and evolution of dolphin, whale blowholes

Modern cetaceans -- which include dolphins, whales and porpoises -- are well adapted for aquatic life. They have blubber to insulate and fins to propel and steer. Today's cetaceans also sport a unique type of nasal passage: It rises at an angle relative to the roof of the mouth -- or palate -- and exits at the top of the head as a blowhole.

This is an apt adaptation for an air-breathing animal at home in the water. Yet as embryos, the cetacean nasal passage starts out in a position more typical of mammals: parallel to the palate and exiting at the tip of the snout, or rostrum. Cetacean experts have long puzzled over how the nasal passage switches during embryonic and fetal development from a palate-parallel pathway to an angled orientation terminating in a blowhole.

"The shift in orientation and position of the nasal passage in cetaceans is a developmental process that's unlike any other mammal," said Rachel Roston, a postdoctoral researcher at the University of Washington School of Dentistry. "It's an interesting question to see what parts remain connected, what parts shift orientation and how might they work together through a developmental process to bring about this change."

New research by Roston and V. Louise Roth, a professor of biology at Duke University, is shedding light on this process. By measuring anatomical details of embryos and fetuses of pantropical spotted dolphins, they determined the key anatomical changes that flip the orientation of the nasal passage up. Their findings, published July 19 in the Journal of Anatomy, are an integrative model for this developmental transition for cetaceans.

"We discovered that there are three phases of growth, primarily in the head, that can explain how the nasal passage shifts in orientation and position," said lead author Roston, who began this study as a doctoral student at Duke.

The three phases of growth are:
 

1. Initially parallel, the roof of the mouth and the nasal passage become separated as the area between them grows into a triangular shape. This phase begins during embryonic development after the face starts forming, which, for the pantropical spotted dolphin, is in the first two months after fertilization.
2. The snout grows longer at an angle to the nasal passage, further separating the nostrils from the tip of the snout. This phase begins later in fetal development and may continue even after birth.
3. The skull folds backward, and the head and body become more aligned. This rotates the nasal passage up so that it becomes nearly vertical relative to the body axis. This phase begins in late embryonic development and continues through fetal development.

"While the nose moves to the top of the head, many of the important angular changes are actually in the bottom, or base, of the skull. That's not necessarily something you'd expect to find!" said Roston.

The three phases of growth do not unfold in a step-by-step process, but instead overlap with each other temporally, Roston said. They represent distinct developmental transformations that, put together, shift the nasal passage to the top of the head.

Roston and Roth developed this model using anatomical data obtained by photographs and CT scans of 21 embryonic and fetal pantropical spotted dolphin specimens held by the Smithsonian Institution's National Museum of Natural History and the Natural History Museum of Los Angeles County. The specimens represented a wide range of embryonic and fetal development.

For comparison, they obtained data from eight fin whale fetuses, also at the National Museum of Natural History, and found significant differences between them and the pantropical spotted dolphin. In fin whales, the skull folded in a region in the back of the skull, near where the skull joins with the vertebral column. In the pantropical spotted dolphin, the folding is centered near the middle of the skull.

The model Roston and Roth developed could inform how scientists view cetacean evolution. These creatures began to evolve from a four-legged, land-dwelling mammalian ancestor, which had a nasal passage parallel to the palate, more than 50 million years ago. As cetaceans evolved, the blowhole gradually migrated from the tip of the snout to the back of the snout, and then gradually up to the top of the skull.

In addition, the two species represent different branches of the cetacean family tree that diverged more than 30 million years ago. Dolphins -- along with porpoises, orcas, sperm whales and beaked whales -- are odontocetes, commonly known as toothed whales. Fin whales are from a group called the baleen whales, named for their distinct feeding apparatus.

"I'm struck by two interesting discoveries that emerged from this work," said Roth. "Although they both develop blowholes, there are key differences between a baleen and a toothed whale in how they reorient their nasal passages during development. Moreover, surprisingly, accompanying the processes of developing upwardly oriented nostrils there are profound changes within the braincase."

In the future, examining more species from both lineages could indicate whether all baleen and toothed whales differ in this manner, Roston said.

"This model gives us a hypothesis for the developmental steps that had to occur to make that anatomical transformation happen, and will serve as a point of comparison for additional studies of growth and development in whales, dolphins and porpoises," said Roston.

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New theory of life’s multiple origins

The history of life on Earth has often been likened to a four-billion-year-old torch relay. One flame, lit at the beginning of the chain, continues to pass on life in the same form all the way down. But what if life is better understood on the analogy of the eye, a convergent organ that evolved from independent origins? What if life evolved not just once, but multiple times independently?

In a new paper, published in the Journal of Molecular Evolution, Santa Fe Institute researchers Chris Kempes and David Krakauer argue that in order to recognize life's full range of forms, we must develop a new theoretical frame.

In their three-layered frame, Kempes and Krakauer call for researchers to consider, first, the full space of materials in which life could be possible; second, the constraints that limit the universe of possible life; and, third, the optimization processes that drive adaptation. In general, the framework considers life as adaptive information and adopts the analogy of computation to capture the processes central to life.

Several significant possibilities emerge when we consider life within the new framework. First, life originates multiple times -- some apparent adaptations are actually "a new form of life, not just an adaptation," explains Krakauer -- and it takes a far broader range of forms than conventional definitions allow.

Culture, computation, and forests are all forms of life in this frame. As Kempes explains, "human culture lives on the material of minds, much like multicellular organisms live on the material of single-celled organisms."

When researchers focus on the life traits of single organisms, they often neglect the extent to which organisms' lives depend upon entire ecosystems as their fundamental material, and also ignore the ways that a life system may be more or less living. Within the Kempes-Krakauer framework, by contrast, another implication appears: life becomes a continuum rather than a binary phenomenon. In this vein, the authors point to a variety of recent efforts that quantitatively place life on a spectrum.

By taking a broader view of life's principles, Kempes and Krakauer hope to generate more fertile theories for studying life. With clearer principles for finding life forms, and a new range of possible life forms that emerges from new principles, we'll not only clarify what life is, explains Krakauer, we'll also be better equipped "to build devices to find life," to create it in labs, and to recognize to what degree the life we see is living.

From Science Daily

Building bonds between males leads to more offspring for chimpanzees

If you're a male chimp looking for love -- or offspring -- it pays to make friends with other males.

A study led by the University of Michigan, in collaboration with Arizona State and Duke universities, examined why male chimpanzees form close relationships with each other, and found that male chimpanzees that build strong bonds with the alpha male of the group, or with a large network of other males, are more successful at siring offspring. The results are published in the journal iScience.

"One big question that biologists have had for a long time is why you see so many friendly behaviors such as cooperation and alliance in animals," said lead study author and U-M postdoctoral researcher Joseph Feldblum. "One would expect to see these social bonds -- or strong, friendly social relationships -- only if they provide some sort of fitness benefit to the individuals. Males wouldn't spend all this time grooming other males and forgoing trying to find females or food unless you get some kind of benefit from it."

One benefit would be the opportunity to sire more offspring, but no previous studies have looked at the link between social relationships and reproductive success in chimpanzees. Much of the research in this area has been done in female primates, who are primarily concerned with accessing resources in order to reproduce quickly. For males, the biggest task is getting reproductive access to females, says Feldblum, also an assistant professor in the U-M Department of Anthropology and member of the Michigan Society of Fellows.

"Chimps cooperate frequently, and often in these very dramatic ways: You see things like grooming, all kinds of complex alliance formation and group territorial defense," Feldblum said. "The question is: What do males get out of it and how?"

It turns out, they get babies.

One function of these social bonds, the researchers found, is to help males gain access to mating opportunities they wouldn't otherwise be able to get without help from their friends. To examine the link between sociality and paternity success, the researchers examined behavioral and genetic data from a population of chimpanzees living in western Tanzania. The group is part of the ongoing study of chimpanzees in Gombe Stream National Park, begun by Jane Goodall in 1960.

The researchers began by constructing a base model that captures the effects of male age, dominance rank and genetic relatedness to the mother on male siring success. They first used the model to look at 56 siring events with known paternity between 1980 and 2014. Then, they tested whether adding measures of male social bonds to the models improved their ability to predict which male would sire a given offspring.

They found that males with more strong association ties -- males with the highest number of social bonds with other males -- had a higher likelihood of siring offspring. In fact, two or more strong association ties meant a male chimpanzee was more than 50% more likely to sire a given offspring, after accounting for the chimp's age, relation to the mother and dominance rank score.

Next, the researchers wanted to understand how a chimp's relationship to the alpha male underpinned male reproductive success. To do this, they examined the role of strong bonds with the alpha male, looking at 45 siring events by non-alpha males. They generated the same base model, this time comparing the model with models that included several measures of bond strength with the alpha male, among other measures.

The model that fit best included what is called the composite sociality index, which includes grooming and association with the alpha male. It showed that subordinate males with strong bonds with the alpha male, as well as those with many strong association ties, were more likely to sire a given offspring.

"Sucking up to the boss is nothing new," said co-author Anne Pusey of Duke University. "We show that it's always paid off."

But the researchers also found that two factors -- a strong bond with the alpha male and many strong association ties -- both independently contributed to reproductive success.

In animal behavior, coalition formation is when two or more individuals jointly direct aggression toward a third or another group of individuals. According to previous research, individuals that are more central in the network of coalitions tend to rise in rank and sire more offspring.

In the current work, the researchers showed that males who form stronger ties are also more likely to form coalitions, and the researchers hypothesize that this larger alliance network helps males gain mating opportunities. They also found that forming these many strong bonds leads to chimps' improvement in rank within the group; those that made it to the alpha position were also more likely to sire offspring.

A clearer idea of the benefits of social relationships in chimpanzees provides clues about the evolution of friendship in humans.

"Together with bonobos, chimpanzees are our closest living relatives, and help us to identify which features of human social life are unique. This study suggests that strong bonds among males have deep evolutionary roots and provided the foundation for the more complex relationships that we see in humans," said senior author Ian Gilby, a researcher at ASU. "This research also highlights the value of long-term studies like these, which are essential for understanding the biology of a species that lives for many decades and is slow to reproduce."

Feldblum says more research is needed to tease out how coalition formations and these social bonds lead to siring success.

"Is it that if your ally is nearby, you're more likely to mate with an estrus female, or does having your allies around you protect you from harassment from other males?" Feldblum said. "Or because your ally will support you if a conflict erupts, your stress levels are lower and you can devote more energy to mating efforts? This last step we still don't know."

Gilby is an associate professor at the School of Human Evolution and Social Change at ASU, and a research affiliate in the Institute of Human Origins, which curates the data used in this study. Pusey, professor emerita at Duke, has spent the last 30 years of her career assembling, organizing and digitizing this unique dataset.

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Mutated enzyme weakens connection between brain cells that help control movement

In one type of a rare, inherited genetic disorder that affects control of body movement, scientists have found a mutation in an enzyme impairs communication between neurons and what should be the inherent ability to pick up our pace when we need to run, instead of walk, across the street.

The disorder is spinocerebellar ataxia, or SCA, a neurodegenerative condition resulting from different genetic mutations whose debilitating bottom line can include ataxia -- loss of control of body movement -- and atrophy of the cerebellum, a small part of the brain jam packed with neurons, which coordinates movement and balance, says Dr. Ferenc Deak, neuroscientist at the Medical College of Georgia at Augusta University.

The enzyme is ELOVL4, which produces very long chain fatty acids, and its mutation is known to cause the specific SCA type 34. Animal models with this SCA type have problems with motor control by age two months, and scientists from MCG and the University of Oklahoma Health Sciences Center wanted to know precisely why.

"We found a dramatically diminished synaptic response. The information was to go faster, go faster and they never really got the message," Deak, co-corresponding author of the study in the journal Molecular Neurobiology, says of these communication connections between neurons. "They were transmitting the signal, but when they had to adjust their synaptic connection to coordinate the different movement, that did not happen in the mutant knock-in rat," he says of the SCA34 model generated using the gene editing technique CRISPR cas9.

Despite the different gene mutations that are causative in SCA, a common bottom line appears to be altered output of the cerebellum and an impact on Purkinje cells, big brain cells in the cerebellum, which can receive about 100 times the input of usual neurons. The big cells also exclusively inhibit communication, so they shut down signals that would interfere with something like a muscle being activated. Loss of these key cells is clear in many forms of SCA, Deak says.

Much like an air traffic controller at a busy airport, these big brain cells obviously monitor a lot of different input simultaneously, and they are the only neuron sending out messages from that part of the brain.

Purkinje cells get a lot of their input from granule cells, one of the smallest neurons in the brain but largest in number. Both cell types express a lot of ELOVL4 and also depend on the enzyme, Deak says. ELOVL4 was known to be important to the communication between these and other cells, but why remained elusive.

The new studies found mutation of ELOVL4 resulted in significant reduction of the ability of synapses that bring messages to and away from Purkinje cells to strengthen their signaling, which is essential in this case to coordinating movement, so you could speed up your pace if needed or move your hands wildly about on command.

Their findings point to the essential role of ELOVL4 in motor function and synaptic plasticity, Deak says.

They also suggest that patients with SCA34 have an impairment and asynchrony in the communication between key neurons in the cerebellum well before their brain shows clear signs of degeneration.

Deak notes that over time, the impaired responses between these constantly communicating cells may lead to the degeneration of the cerebellum often found in patients when they first go to their doctor with complaints about problems with walking, talking and other movement.

But in their model of SCA34, the structure of the cerebellum looked normal up to six months of age, even though the animal models clearly had the expected motor deficits, the scientists report.

They found the synapses also were intact and functioning at a basic level that enables the rats to, for example, walk normally, but in these knock-in rats the usual plasticity or flexibility was lacking. Rather synapses in the mutant couldn't increase signaling and make that transition.

ELOVL4 can make both saturated and unsaturated very long chain fatty acids -- dubbed "long" because of the large number of carbon atoms they contain -- depending on which tissue the enzyme is in. In the cerebellum, it enables Purkinje and granule cells to make saturated very long chain fatty acids, which were known to be important to synaptic function, Deak says. But exactly how they are important was an unknown.

The scientists think the weakened synaptic responsiveness they found is a quantity problem: the mutated enzyme makes about 70% of the usual amount of very long chain fatty acids, which appears to be the threshold for gait problems. If the cells produced none, it would result in excessive seizures and death as Deak has seen in other models.

Their current research includes finding ways to deliver more saturated very long chain fatty acids to the brain. The scientists have a patent pending on one way to make this maneuver, which is made tougher by the fact that when you produce saturated very long chain fatty acids they have the consistency of candle wax, Deak says, which the rats don't even digest, just poop out.

Very long chain fatty acids are essential to life but their exact roles are mostly elusive, the scientists say.

"What we know from our work is that they are a very important component for certain cell membranes," Deak says, like the membranes of some excitatory and inhibitory neurons as well as skin cells. In fact, the scientists have shown that when ELOVL4 is missing in the skin, body fluids seep through the skin, our largest natural barrier. In generating other ELOVL4 mutant mice models they had to overexpress ELOVL4 specifically in the skin to enable survival, Deak said.

Deak's research has shown that these saturated very long chain fatty acids also like to accumulate and strengthen vesicles, tiny traveling compartments that can move about inside cells, so they are better able to get to their destination before they fuse with a cell membrane. Fusing is necessary for neurotransmission -- one of the things vesicles in the brain transport is chemical messengers called neurotransmitters -- but unregulated fusion is bad.

The scientists documented its impact when they found that mice with two mutant copies of ELOVL4 died of seizures. While they were making these findings in the laboratory, there were reports out of Saudi Arabia about children having the same mutations and issues, he says. In fact, it was Deak's research interest in seizures that prompted his pursuit of better understanding the roles of very long chain fatty acids. He suspects they have a role in his other interest as well: the aging brain and Alzheimer's.

A team led by Dr. Martin-Paul Agbaga created the "knock-in" rat model of the human condition SCA34, which has been identified in one French-Canadian family and three Japanese families. In these individuals, skin problems can surface from shortly after birth to adolescence, and movement problems and typically progressive movement issues start surfacing in their 30s.

Agbaga, co-corresponding author of the new paper and one of Deak's longtime collaborators, is a vision scientist and cell biologist at the University of Oklahoma Health Sciences Center Department of Ophthalmology and Dean McGee Eye Institute.

Dr. Robert E. Anderson, professor of vision research at the Dean McGee Eye Institute, founder of the ELOVL4 research group in Oklahoma, and a worldwide leader of research on lipid pathophysiology in the retina, is a coauthor on the paper. Deak came to MCG from the University of Oklahoma Health Sciences Center last year.

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Nearby star-forming region yields clues to the formation of our solar system

A region of active star formation in the constellation Ophiuchus is giving astronomers new insights into the conditions in which our own solar system was born. In particular, a new study of the Ophiuchus star-forming complex shows how our solar system may have become enriched with short-lived radioactive elements.

Evidence of this enrichment process has been around since the 1970s, when scientists studying certain mineral inclusions in meteorites concluded that they were pristine remnants of the infant solar system and contained the decay products of short-lived radionuclides. These radioactive elements could have been blown onto the nascent solar system by a nearby exploding star (a supernova) or by the strong stellar winds from a type of massive star known as a Wolf-Rayet star.

The authors of the new study, published August 16 in Nature Astronomy, used multi-wavelength observations of the Ophiuchus star-forming region, including spectacular new infrared data, to reveal interactions between the clouds of star-forming gas and radionuclides produced in a nearby cluster of young stars. Their findings indicate that supernovas in the star cluster are the most likely source of short-lived radionuclides in the star-forming clouds.

"Our solar system was most likely formed in a giant molecular cloud together with a young stellar cluster, and one or more supernova events from some massive stars in this cluster contaminated the gas which turned into the sun and its planetary system," said coauthor Douglas N. C. Lin, professor emeritus of astronomy and astrophysics at UC Santa Cruz. "Although this scenario has been suggested in the past, the strength of this paper is to use multi-wavelength observations and a sophisticated statistical analysis to deduce a quantitative measurement of the model's likelihood."

First author John Forbes at the Flatiron Institute's Center for Computational Astrophysics said data from space-based gamma-ray telescopes enable the detection of gamma rays emitted by the short-lived radionuclide aluminum-26. "These are challenging observations. We can only convincingly detect it in two star-forming regions, and the best data are from the Ophiuchus complex," he said.

The Ophiuchus cloud complex contains many dense protostellar cores in various stages of star formation and protoplanetary disk development, representing the earliest stages in the formation of a planetary system. By combining imaging data in wavelengths ranging from millimeters to gamma rays, the researchers were able to visualize a flow of aluminum-26 from the nearby star cluster toward the Ophiuchus star-forming region.

"The enrichment process we're seeing in Ophiuchus is consistent with what happened during the formation of the solar system 5 billion years ago," Forbes said. "Once we saw this nice example of how the process might happen, we set about trying to model the nearby star cluster that produced the radionuclides we see today in gamma rays."

Forbes developed a model that accounts for every massive star that could have existed in this region, including its mass, age, and probability of exploding as a supernova, and incorporates the potential yields of aluminum-26 from stellar winds and supernovas. The model enabled him to determine the probabilities of different scenarios for the production of the aluminum-26 observed today.

"We now have enough information to say that there is a 59 percent chance it is due to supernovas and a 68 percent chance that it's from multiple sources and not just one supernova," Forbes said.

This type of statistical analysis assigns probabilities to scenarios that astronomers have been debating for the past 50 years, Lin noted. "This is the new direction for astronomy, to quantify the likelihood," he said.

The new findings also show that the amount of short-lived radionuclides incorporated into newly forming star systems can vary widely. "Many new star systems will be born with aluminum-26 abundances in line with our solar system, but the variation is huge -- several orders of magnitude," Forbes said. "This matters for the early evolution of planetary systems, since aluminum-26 is the main early heating source. More aluminum-26 probably means drier planets."

The infrared data, which enabled the team to peer through dusty clouds into the heart of the star-forming complex, was obtained by coauthor João Alves at the University of Vienna as part of the European Southern Observatory's VISION survey of nearby stellar nurseries using the VISTA telescope in Chile.

"There is nothing special about Ophiuchus as a star formation region," Alves said. "It is just a typical configuration of gas and young massive stars, so our results should be representative of the enrichment of short-lived radioactive elements in star and planet formation across the Milky Way."

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Cities are making mammals bigger

A new study shows urbanization is causing many mammal species to grow bigger, possibly because of readily available food in places packed with people.

The finding runs counter to many scientists' hypothesis that cities would trigger mammals to get smaller over time. Buildings and roads trap and re-emit a greater degree of heat than green landscapes, causing cities to have higher temperatures than their surroundings, a phenomenon known as the urban heat island effect. Animals in warmer climates tend to be smaller than the same species in colder environments, a classic biological principle called Bergmann's Rule.

But Florida Museum of Natural History researchers discovered an unexpected pattern when they analyzed nearly 140,500 measurements of body length and mass from more than 100 North American mammal species collected over 80 years: City-dwelling mammals are both longer and heftier than their rural counterparts.

"In theory, animals in cities should be getting smaller because of these heat island effects, but we didn't find evidence for this happening in mammals," said study lead author Maggie Hantak, a Florida Museum postdoctoral researcher. "This paper is a good argument for why we can't assume Bergmann's Rule or climate alone is important in determining the size of animals."

Hantak and her collaborators created a model that examined how climate and the density of people living in a given area -- a proxy for urbanization -- influence the size of mammals. As temperatures dropped, both body length and mass increased in most mammal species studied, evidence of Bergmann's Rule at work, but the trend was stronger in areas with more people.

Surprisingly, mammals in cities generally grew larger regardless of temperature, suggesting urbanization rivals or exceeds climate in driving mammal body size, said Robert Guralnick, Florida Museum curator of biodiversity informatics.

"That wasn't what we expected to find at all," he said. "But urbanization represents this new disturbance of the natural landscape that didn't exist thousands of years ago. It's important to recognize that it's having a huge impact."

About a decade ago, scientists began to raise the alarm that warmer temperatures brought by climate change are causing many animal species to grow smaller over time. While many of the consequences of shifting body size are unknown, researchers cautioned that smaller animals may have smaller or fewer offspring, creating a feedback loop, and shrinking prey could also put pressure on meat-eaters to find more resources.

Guralnick and Hantak said they hope their findings will lead more researchers to add urbanization to their analyses of changing body size.

"When we think about what's going to happen to mammalian body size over the next 100 years, a lot of people frame that as global warming causing animals to get smaller," Guralnick said. "What if that isn't the biggest effect? What if it's that urbanization is going to lead to fatter mammals?"

Not all animals respond to human-induced environmental changes in the same way, Hantak added. The researchers also investigated how the effects of climate and urbanization may be tempered or amplified by the behavior and habits of certain species.

They found animals that use hibernation or torpor, a temporary way of slowing metabolic rate and dropping body temperature, shrank more dramatically in response to increases in temperature than animals without these traits. The finding could have important implications for conservation efforts, Hantak said.

"We thought species that use torpor or hibernation would be able to hide from the effects of unfavorable temperatures, but it seems they're actually more sensitive," she said.

While cities radically transform the landscape, they provide animals with new opportunities as well as threats, Guralnick said. The abundance of food, water and shelter and relative lack of predators in cities may help certain species succeed in comparison with their neighbors in rural areas. The results of the 2020 U.S. Census show that almost all human population growth over the past decade has occurred in the nation's metro areas. As urbanization ramps up, animals could be divided into "winners and losers," and mammal distributions may shift, he said.

"Animals that like living in urban environments could have a selective advantage while other species may lose out because of the continued fragmentation of landscapes," Guralnick said. "This is relevant to how we think about managing suburban and urban areas and our wildlands in 100 years."

While bigger is often better biologically, the long-term consequences to urban mammals of eating a diet of human food waste have yet to be determined, Hantak said.

"When you change size, it could change your whole lifestyle," she said.

Hantak and her collaborators were able to conduct the study thanks to thousands of measurements collected by natural historians in the field and museums. The research team used information from three databases: VertNet, the National Science Foundation's National Ecological Observatory Network (NEON) and the North American Census of Small Mammals (NASCM). Cumulatively, this data offers a broadscale view of how increasing urbanization is impacting mammals with very different life histories, from wolves, bobcats and deer to bats, shrews and rodents, Guralnick said.

"Museum collections have the power to tell us stories about the natural world," he said. "Because we have these collections, we can ask questions about what mammals looked like before humans dominated the landscape. Digitizing specimen data unlocks these resources so that everyone can make discoveries about our planet."

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Pollinators: First global risk index for species declines and effects on humanity

Disappearing habitats and use of pesticides are driving the loss of pollinator species around the world, posing a threat to "ecosystem services" that provide food and wellbeing to many millions -- particularly in the Global South -- as well as billions of dollars in crop productivity.

This is according to an international panel of experts, led by the University of Cambridge, who used available evidence to create the first planetary risk index of the causes and effects of dramatic pollinator declines in six global regions.

The bees, butterflies, wasps, beetles, bats, flies and hummingbirds that distribute pollen, vital for the reproduction of over 75% of food crops and flowering plants -- including coffee, rapeseed and most fruits -- are visibly diminishing the world over, yet little is known of the consequences for human populations.

"What happens to pollinators could have huge knock-on effects for humanity," said Dr Lynn Dicks from Cambridge's Department of Zoology. "These small creatures play central roles in the world's ecosystems, including many that humans and other animals rely on for nutrition. If they go, we may be in serious trouble."

Dicks assembled a 20-strong team of scientists and indigenous representatives to attempt an initial evaluation of the drivers and risks for pollinator declines worldwide. The research is published today in Nature Ecology & Evolution.

The top three global causes of pollinator loss are habitat destruction, followed by land management -- primarily the grazing, fertilizers and crop monoculture of farming -- and then widespread pesticide use, according to the study. The effect of climate change comes in at number four, although data are limited.

Perhaps the biggest direct risk to humans across all regions is "crop pollination deficit": falls in quantity and quality of food and biofuel crops. Experts ranked the risk of crop yield "instability" as serious or high across two-thirds of the planet -- from Africa to Latin America -- where many rely directly on pollinated crops through small-holder farming.

"Crops dependent on pollinators fluctuate more in yield than, for example, cereals," said Dicks. "Increasingly unusual climatic phenomena, such as extreme rainfall and temperature, are already affecting crops. Pollinator loss adds further instability -- it's the last thing people need."

A major 2016 report to which Lynn Dicks contributed suggested there has been up to a 300% increase in pollinator-dependent food production over the past half century, with an annual market value that may be as much as US$577 billion.

Reduced species diversity was seen as a high-ranking global risk to humans, which not only risks food security but a loss of "aesthetic and cultural value." These species have been emblems of nature for millennia, argue the experts, and too little consideration is given to how their declines affect human wellbeing.

"Pollinators have been sources of inspiration for art, music, literature and technology since the dawn of human history," said Dicks. "All the major world religions have sacred passages about bees. When tragedy struck Manchester in 2017, people reached for bees as a symbol of community strength."

"Pollinators are often the most immediate representatives of the natural world in our daily lives. These are the creatures that captivate us early in life. We notice and feel their loss. Where are the clouds of butterflies in the late summer garden, or the myriad moths fluttering in through open windows at night?"

"We are in the midst of a species extinction crisis, but for many people that is intangible. Perhaps pollinators are the bellwether of mass extinction," said Dicks.

Loss of access to "managed pollinators" such as industrial beehives was ranked as a high risk to North American society, where they boost crops including apples and almonds, and have suffered serious declines from disease and 'colony collapse disorder'.

The impact of pollinator decline on wild plants and fruits was viewed a serious risk in Africa, Asia-Pacific and Latin America -- regions with many low-income countries where rural populations rely on wild-growing foods.

In fact, Latin America was viewed as the region with most to lose. Insect-pollinated crops such as cashew, soybean, coffee and cocoa are essential to regional food supply and international trade right across the continent. It is also home to large indigenous populations reliant on pollinated plants, with pollinator species such as hummingbirds embedded in oral culture and history.

Asia Pacific was another global region where pollinator decline was perceived to pose serious risks to human well-being. China and India are increasingly reliant on fruit and vegetable crops that need pollinators, some of which now require people to pollinate by hand.

The researchers caution that not enough is known about the state of pollinator populations in the Global South, as evidence of decline is still primarily from wealthy regions such as Europe (where at least 37% of bee and 31% of butterfly species are in decline). Pollination deficits and biodiversity loss were seen as the biggest risks to Europeans, with potential to affect crops ranging from strawberries to oilseed rape.

Dr Tom Breeze, co-author and Ecological Economics Research Fellow at the University of Reading, said: "This study highlights just how much we still don't know about pollinator decline and the impacts this has on human societies, particularly in parts of the developing world.

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Having a good listener improves your brain health

Supportive social interactions in adulthood are important for your ability to stave off cognitive decline despite brain aging or neuropathological changes such as those present in Alzheimer's disease, a new study finds.

In the study publishing August 16 in JAMA Network Open, researchers observed that simply having someone available most or all of the time whom you can count on to listen to you when you need to talk is associated with greater cognitive resilience -- a measure of your brain's ability to function better than would be expected for the amount of physical aging- or disease-related changes in the brain, which many neurologists believe can be boosted by engaging in mentally stimulating activities, physical exercise, and positive social interactions.

"We think of cognitive resilience as a buffer to the effects of brain aging and disease," says lead researcher Joel Salinas, MD, the Lulu P. and David J. Levidow Assistant Professor of Neurology at NYU Grossman School of Medicine and member of the Department of Neurology's Center for Cognitive Neurology. "This study adds to growing evidence that people can take steps, either for themselves or the people they care about most, to increase the odds they'll slow down cognitive aging or prevent the development of symptoms of Alzheimer's disease -- something that is all the more important given that we still don't have a cure for the disease."

An estimated 5 million Americans are living with Alzheimer's disease, a progressive condition that affects mostly those over 65 and interferes with memory, language, decision-making, and the ability to live independently. Salinas says that while the disease usually affects an older population, the results of this study indicate that people younger than 65 would benefit from taking stock of their social support. For every unit of decline in brain volume, individuals in their 40s and 50s with low listener availability had a cognitive age that was four years older than those with high listener availability.

"These four years can be incredibly precious. Too often we think about how to protect our brain health when we're much older, after we've already lost a lot of time decades before to build and sustain brain-healthy habits," says Salinas. "But today, right now, you can ask yourself if you truly have someone available to listen to you in a supportive way, and ask your loved ones the same. Taking that simple action sets the process in motion for you to ultimately have better odds of long-term brain health and the best quality of life you can have."

Salinas also recommends that physicians consider adding this question to the standard social history portion of a patient interview: asking patients whether they have access to someone they can count on to listen to them when they need to talk. "Loneliness is one of the many symptoms of depression, and has other health implications for patients," says Salinas. "These kinds of questions about a person's social relationships and feelings of loneliness can tell you a lot about a patient's broader social circumstances, their future health, and how they're really doing outside of the clinic."

How the Study Was Conducted

Researchers used one of the longest running and most closely monitored community-based cohorts in the U.S., the Framingham Heart Study (FHS), as the source of their study's 2,171 participants, with an average age of 63. FHS participants self-reported information on the availability of supportive social interactions including listening, good advice, love and affection, sufficient contact with people they're close with, and emotional support.

Study participants' cognitive resilience was measured as the relative effect of total cerebral brain volume on global cognition, using MRI scans and neuropsychological assessments taken as part of the FHS. Lower brain volumes tend to associate with lower cognitive function, and in this study, researchers examined the modifying effect of individual forms of social support on the relationship between cerebral volume and cognitive performance.

The cognitive function of individuals with greater availability of one specific form of social support was higher relative to their total cerebral volume. This key form of social support was listener availability and it was highly associated with greater cognitive resilience.

Researchers note that further study of individual social interactions may improve understanding of the biological mechanisms that link psychosocial factors to brain health. "While there is still a lot that we don't understand about the specific biological pathways between psychosocial factors like listener availability and brain health, this study gives clues about concrete, biological reasons why we should all seek good listeners and become better listeners ourselves," says Salinas.

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Metabolism changes with age, just not when you might think

Most of us remember a time when we could eat anything we wanted and not gain weight. But a new study suggests your metabolism, the rate at which you burn calories, actually peaks much earlier and starts its inevitable decline later than you might think.

The findings appear in the journal Science.

"As we age, there are a lot of physiological changes that occur in the phases of our life such as during puberty and in menopause. . What's odd is that the timing of our 'metabolic life stages' doesn't appear to match the markers we associate with growing up and getting older," said study co-author Jennifer Rood, PhD, Associate Executive Director for Cores and Resources at Pennington Biomedical Research Center.

Four Pennington Biomedical researchers were part of an international team of scientists who analyzed the average calories burned by more than 6,600 people as they went about their daily lives. The participants' ages ranged from one week old to 95 years, and they lived in 29 different countries. The other Pennington Biomedical scientists are Peter Katzmarzyk, PhD, Associate Executive Director for Population and Public Health Sciences; Corby Martin, PhD, Professor and Director, Ingestive Behavior Laboratory; and Eric Ravussin, PhD, Associate Executive Director for Clinical Science.

Most previous large-scale studies measured how much energy the body uses for basic vital functions -- breathing, digesting, and pumping blood -- the calories you need just to stay alive. But basic functions account for just 50 percent to 70 percent of the calories we burn each day. They don't include the energy we spend doing everything else: washing the dishes, walking the dog, breaking a sweat at the gym, even just thinking or fidgeting.

To come up with a number for total daily energy expenditure, the researchers turned to the "doubly labeled water" method. It's a urine test that involves having a person drink water in which the hydrogen and oxygen in the water molecules have been replaced with naturally occurring "heavy" forms, and then measures how quickly they're flushed out.

Scientists have used the technique -- considered the gold standard for measuring daily energy expenditure during normal daily life outside of the lab -- to measure energy expenditure in humans since the 1980s. But previous studies were limited in size and scope due to cost. To get around that limitation, multiple labs shared their data in a single database, to see if they could tease out truths hidden or only hinted at in previous studies.

Pooling and analyzing energy expenditures across the entire lifespan revealed some surprises.

"Some people think of their teens and 20s as the age when their calorie-burning potential hits its peak," Dr. Katzmarzyk said. "But the study shows that, pound for pound, infants had the highest metabolic rates of all."

Energy needs shoot up during the first 12 months of life. By their first birthdays, babies burn calories 50 percent faster for their body size than adults.

And that's not just because infants are busy tripling their birth weight in their first year.

"The babies grow rapidly, which accounts for much of the effect. However, after you control for this, their energy expenditures tend to be higher than what you would expect for their body size," Dr. Martin said.

An infant's explosive metabolism may help explain why children who don't get enough to eat during this developmental stage are less likely to survive and grow up to be healthy adults.

"More research is needed to better understand the metabolism of babies. We need to know what is driving higher energy expenditures," Dr. Martin said.

After the initial surge in infancy, a person's metabolism slows by about 3 percent each year until our 20s, when it levels off into a new normal.

Surprisingly, the growth spurts of adolescence didn't generate an increase in daily calorie needs after researchers took body size into account. Another surprise? People's metabolisms were most stable from their 20s through their 50s. Calorie needs during pregnancy grew no more than expected.

The findings suggest that other factors lie behind the so-called "middle-age spread."

The data suggest that our metabolisms don't really start to decline again until after age 60. The slowdown is gradual, only 0.7 percent a year. But a person in their 90s needs 26 percent fewer calories each day than someone in midlife.

Lost muscle mass as we get older may be partly to blame, the researchers say, since muscle burns more calories than fat. But it's not the whole picture.

"We took dwindling muscle mass into account. After 60, a person's cells slow down," Dr. Ravussin said.

The patterns held even when differing activity levels were taken into account.

Aging goes hand in hand with so many other physiological changes that it has been difficult to parse what drives the shifts in energy expenditure. But the new research supports the idea that it's more than age-related changes in lifestyle or body composition.

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Study reveals missing link between high-fat diet, microbiota and heart disease

A high-fat diet disrupts the biology of the gut's inner lining and its microbial communities -- and promotes the production of a metabolite that may contribute to heart disease, according to a study published Aug. 13 in the journal Science.

The discoveries in animal models support a key role for the intestines and microbiota in the development of cardiovascular disease, said Mariana Byndloss, DVM, PhD, assistant professor of Pathology, Microbiology and Immunology at Vanderbilt University Medical Center.

The intestines, she noted, have been relatively understudied by scientists seeking to understand the impact of obesity.

"Before COVID, obesity and metabolic syndrome were considered the pandemic of the 21st century. Right now, roughly 40% of the U.S. population is obese, and that percentage is predicted to climb," Byndloss said. "Our research has revealed a previously unexplored mechanism for how diet and obesity can increase risk of cardiovascular disease -- by affecting the relationship between our intestines and the microbes that live in our gut."

In previous studies, Byndloss and Andreas Bäumler, PhD, at the University of California at Davis, found that the epithelial cells lining the intestines and gut microbes share a mutually beneficial relationship that promotes a healthy gut environment. They wondered if diseases like obesity affect this relationship.

The collaborating research teams found that a high-fat diet causes inflammation and damages intestinal epithelial cells in animal models. The high-fat diet impairs the function of energy-generating mitochondria, Byndloss explained, causing the intestinal cells to produce more oxygen and nitrate.

These factors, in turn, stimulate the growth of harmful Enterobacteriaceae microbes, such as E. coli, and boost bacterial production of a metabolite called TMA (trimethylamine). The liver converts TMA to TMAO (trimethylamine-N-oxide), which has been implicated in promoting atherosclerosis and increasing the relative risk for all-cause mortality in patients.

"It was known that exposure to a high-fat diet causes dysbiosis -- an imbalance in the microbiota favoring harmful microbes, but we didn't know why or how this was happening," Byndloss said. "We show one way that diet directly affects the host and promotes the growth of bad microbes."

The researchers demonstrated that a drug currently approved for treatment of inflammatory bowel disease restored the function of intestinal epithelial cells and blunted the increase in TMAO in the animal models. The drug, called 5-aminosalicylic acid, activates mitochondrial bioenergetics in the intestinal epithelium.

"This is evidence that it's possible to prevent the negative outcomes associated with a high-fat diet," Byndloss said. A drug such as 5-aminosalicylic acid might be used in conjunction with a probiotic to both restore a healthy intestinal environment and boost beneficial microbe levels, she added.

"Only by fully understanding the relationship between the host -- us -- and gut microbes during health and disease are we going to be able to design therapies that will be effective in controlling obesity and obesity-associated outcomes like cardiovascular disease."

Byndloss and her team plan to extend their studies into animal models of cardiovascular disease. They also are exploring the role of the host-microbe relationship in the development of other diseases including colorectal cancer.

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