It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Friday, October 27, 2023
AI can alert urban planners and policymakers to cities’ decay
More than two-thirds of the world’s population is expected to live in cities by 2050, according to the United Nations. As urbanization advances around the globe, researchers at the University of Notre Dame and Stanford University said the quality of the urban physical environment will become increasingly critical to human well-being and to sustainable development initiatives.
However, measuring and tracking the quality of an urban environment, its evolution and its spatial disparities is difficult due to the amount of on-the-ground data needed to capture these patterns. To address the issue, Yong Suk Lee, assistant professor of technology, economy and global affairs in the Keough School of Global Affairs at the University of Notre Dame, and Andrea Vallebueno from Stanford University used machine learning to develop a scalable method to measure urban decay at a spatially granular level over time.
“As the world urbanizes, urban planners and policymakers need to make sure urban design and policies adequately address critical issues such as infrastructure and transportation improvements, poverty and the health and safety of urbanites, as well as the increasing inequality within and across cities,” Lee said. “Using machine learning to recognize patterns of neighborhood development and urban inequality, we can help urban planners and policymakers better understand the deterioration of urban space and its importance in future planning.”
Traditionally, the measurement of urban quality and quality of life in urban spaces has used sociodemographic and economic characteristics such as crime rates and income levels, survey data of urbanites’ perception and valued attributes of the urban environment, or image datasets describing the urban space and its socioeconomic qualities. The growing availability of street view images presents new prospects in identifying urban features, Lee said, but the reliability and consistency of these methods across different locations and time remains largely unexplored.
In their study, Lee and Vallebueno used the YOLOv5 model (a form of artificial intelligence that can detect objects) to detect eight object classes that indicate urban decay or contribute to an unsightly urban space — things like potholes, graffiti, garbage, tents, barred or broken windows, discolored or dilapidated façades, weeds and utility markings. They focused on three cities: San Francisco, Mexico City and South Bend, Indiana. They chose neighborhoods in these cities based on factors including urban diversity, stages of urban decay and the authors’ familiarity with the cities.
Using comparative data, they evaluated their method in three contexts: homelessness in the Tenderloin District of San Francisco between 2009 and 2021, a set of small-scale housing projects carried out in 2017 through 2019 in a subset of Mexico City neighborhoods, and the western neighborhoods of South Bend in the 2011 through 2019 period — a part of the city that had been declining for decades but also saw urban revival initiatives.
Researchers found that the trained model could adequately detect the objects it sought across different cities and neighborhoods, and did especially well where there are denser populations, such as San Francisco.
For instance, the maps allowed researchers to assess the temporal and geographic variation in homelessness in the San Francisco area, an issue that has grown over the years.
The model struggled in the more suburban area of South Bend, according to Lee, demonstrating a need to tweak the model and the types of objects identified in less dense populations. In addition, the researchers found there is still a risk for bias that should be addressed.
“Our findings indicate that trained models such as ours are capable of detecting the incidences of decay across different neighborhoods and cities, highlighting the potential of this approach to be scaled in order to track urban quality and change for urban centers across the U.S. and cities in other countries where street view imagery is available,” he said.
Lee said the model has potential to provide valuable information using data that can be collected in a more efficient way compared to using coarser, traditional economic data sources, and that it could be a valuable and timely tool for the government, nongovernmental organizations and the public.
“We found that our approach can employ machine learning to effectively track urban quality and change across multiple cities and urban areas,” Lee said. “This type of data could then be used to inform urban policy and planning and the social issues that are impacted by urbanization, including homelessness.”
Contact: Tracy DeStazio, associate director of media relations, 574-631-9958 or tdestazi@nd.edu
A new sounding rocket mission is headed to space to understand how explosive stellar deaths lay the groundwork for new star systems. The Integral Field Ultraviolet Spectroscopic Experiment, or INFUSE, sounding rocket mission, will launch from the White Sands Missile Range in New Mexico on Oct. 29, 2023, at 9:35 p.m. MDT.
For a few months each year, the constellation Cygnus (Latin for “swan”) swoops through the northern hemisphere’s night sky. Just above its wing is a favorite target for backyard astronomers and professional scientists alike: the Cygnus Loop, also known as the Veil Nebula.
The Cygnus Loop is the remnant of a star that was once 20 times the size of our Sun. Some 20,000 years ago, that star collapsed under its own gravity and erupted into a supernova. Even from 2,600 light-years away, astronomers estimate the flash of light would have been bright enough to see from Earth during the day.
Supernovae are part of a great life cycle. They spray heavy metals forged in a star’s core into the clouds of surrounding dust and gas. They are the source of all chemical elements in our universe heavier than iron, including those that make up our own bodies. From the churned-up clouds and star stuff left in their wake, gases and dust from supernovae gradually clump together to form planets, stars, and new star systems.
“Supernovae like the one that created the Cygnus Loop have a huge impact on how galaxies form,” said Brian Fleming, a research professor at the University of Colorado Boulder and principal investigator for the INFUSE mission.
The Cygnus Loop provides a rare look at a supernova blast still in progress. Already over 120 light-years across, the massive cloud is still expanding today at approximately 930,000 miles per hour (about 1.5 million kilometers per hour).
What our telescopes capture from the Cygnus Loop is not the supernova blast itself. Instead, we see the dust and gas superheated by the shock front, which glows as it cools back down.
“INFUSE will observe how the supernova dumps energy into the Milky Way by catching light given off just as the blast wave crashes into pockets of cold gas floating around the galaxy,” Fleming said.
To see that shock front at its sizzling edge, Fleming and his team have developed a telescope that measures far-ultraviolet light – a kind of light too energetic for our eyes to see. This light reveals gas at temperatures between 90,000 and 540,000 degrees Fahrenheit (about 50,000 to 300,000 degrees Celsius) that is still sizzling after impact.
INFUSE is an integral field spectrograph, the first instrument of its kind to fly to space. The instrument combines the strengths of two ways of studying light: imaging and spectroscopy. Your typical telescopes have cameras that excel at creating images – showing where light is coming from, faithfully revealing its spatial arrangement. But telescopes don’t separate light into different wavelengths or “colors” – instead, all of the different wavelengths overlap one another in the resulting image.
Spectroscopy, on the other hand, takes a single beam of light and separates it into its component wavelengths or spectrum, much as a prism separates light into a rainbow. This procedure reveals all kinds of information about what the light source is made of, its temperature, and how it is moving. But spectroscopy can only look at a single sliver of light at a time. It’s like looking at the night sky through a narrow keyhole.
The INFUSE instrument captures an image and then “slices” it up, lining up the slices into one giant “keyhole.” The spectrometer can then spread each of the slices into its spectrum. This data can be reassembled into a 3-dimensional image that scientists call a “data cube” – like a stack of images where each layer reveals a specific wavelength of light.
Using the data from INFUSE, Fleming and his team will not only identify specific elements and their temperatures, but they’ll also see where those different elements lie along the shock front.
“It’s a very exciting project to be a part of,” said lead graduate student Emily Witt, also at CU Boulder, who led most of the assembly and testing of INFUSE and will lead the data analysis. “With these first-of-their-kind measurements, we will better understand how these elements from the supernova mix with the environment around them. It’s a big step toward understanding how material from supernovas becomes part of planets like Earth and even people like us.”
To get to space, the INFUSE payload will fly aboard a sounding rocket. These nimble, crewless rockets launch into space for a few minutes of data collection before falling back to the ground. The INFUSE payload will fly aboard a two-stage Black Brant 9 sounding rocket, aiming for a peak altitude of about 150 miles (240 kilometers), where it will make its observations, before parachuting back to the ground to be recovered. The team hopes to upgrade the instrument and launch again. In fact, parts of the INFUSE rocket are themselves repurposed from the DEUCE mission, which launched from Australia in 2022.
University of Maryland researchers studying how lithium batteries fail have developed a new technology that could enable next-generation electric vehicles (EVs) and other devices that are less prone to battery fires while increasing energy storage.
The innovative method, presented in a paper published Wednesday in the journal Nature, suppresses the growth of lithium dendrites—damaging branch-like structures that develop inside so-called all-solid-state lithium batteries, preventing firms from broadly commercializing the promising technology. But this new design for a battery “interlayer,” led by Department of Chemical and Biomolecular Engineering Professor Chunsheng Wang, stops dendrite formation, and could open the door for production of viable all-solid-state batteries for EVs.
At least 750,000 registered EVs in the U.S. run on lithium-ion batteries—popular because of their high energy storage but containing a flammable liquid electrolyte component that burns when overheated. While no government agency tracks vehicle fires by type of car, and electric car battery fires appear to be relatively rare, they pose particular risks; the National Transportation Safety Board reports that first responders are vulnerable to safety risks, including electric shock and the exposure to toxic gasses emanating from damaged or burning batteries.
All-solid-state batteries could lead to cars that are safer than current electric or internal combustion models, but creating a strategy to bypass the drawbacks was laborious, Wang said. When these batteries are operated at the high capacities and charging-discharging rates that electric vehicles demand, lithium dendrites grow toward the cathode side, causing short circuits and a decay in capacity.
He and Postdoctoral Associate Hongli Wan began to develop a theory for the formation of lithium dendrite growth in 2021; it remains a matter of scientific debate, the researchers said.
“After we figured out that part, we proposed the idea to redesign the interlayers that would effectively suppress the lithium dendrite growth,” he said.
Their solution is unique because of the stabilizing of the battery’s interfaces between the solid electrolyte and the anode (where electrons from a circuit enter the battery) and the electrolyte and the cathode (where energy flows out of the battery). The new battery structure adds a fluorine-rich interlayer that stabilizes the cathode side, as well as a modification of the anode’s interlayer with magnesium and bismuth—suppressing the lithium dendrite.
“Solid-state batteries are next-generation because they can achieve high energy and safety. In current batteries, if you achieve high energy, you’ll sacrifice safety,” said Wang.
Researchers have other challenges to solve before the product enters the market. To commercialize all-solid-state batteries, experts will have to scale down the solid electrolyte layer to achieve a similar thickness to the lithium-ion batteries’ electrolyte, which will improve energy density—or how much power the battery can store. High costs of basic materials are another challenge, the team said.
Aiming to release the new batteries to the market by 2026, advanced battery manufacturer Solid Power plans to begin trials of the new technology to assess its potential for commercialization. Continuing research aims to further boost energy density, the researchers said.
SPIE--INTERNATIONAL SOCIETY FOR OPTICS AND PHOTONICS
IMAGE:
LEVERAGING SPATIAL COHERENCE AS A PHYSICAL PRIOR TO GUIDE THE TRAINING OF A DEEP NEURAL NETWORK, TWC-SWIN METHOD EXCELS AT CAPTURING BOTH LOCAL AND GLOBAL IMAGE FEATURES AND ELIMINATES IMAGE DEGRADATION CAUSED BY ARBITRARY TURBULENCE.
CREDIT: X. TONG ET AL., DOI 10.1117/1.AP.5.6.066003.
Holographic imaging has always been challenged by unpredictable distortions in dynamic environments. Traditional deep learning methods often struggle to adapt to diverse scenes due to their reliance on specific data conditions.
To tackle this problem, researchers at Zhejiang University delved into the intersection of optics and deep learning, uncovering the key role of physical priors in ensuring the alignment of data and pre-trained models. They explored the impact of spatial coherence and turbulence on holographic imaging and proposed an innovative method, TWC-Swin, to restore high-quality holographic images in the presence of these disturbances. Their research is reported in the Gold Open Access journal Advanced Photonics.
Spatial coherence is a measure of how orderly light waves behave. When light waves are chaotic, holographic images become blurry and noisy, as they carry less information. Maintaining spatial coherence is crucial for clear holographic imaging.
Dynamic environments, like those with oceanic or atmospheric turbulence, introduce variations in the refractive index of the medium. This disrupts the phase correlation of light waves and distorts spatial coherence. Consequently, the holographic image may become blurred, distorted, or even lost.
The researchers at Zhejiang University developed the TWC-Swin method to address these challenges. TWC-Swin, short for "train-with-coherence swin transformer," leverages spatial coherence as a physical prior to guide the training of a deep neural network. This network, based on the Swin transformer architecture, excels at capturing both local and global image features.
To test their method, the authors designed a light processing system that produced holographic images with varying spatial coherence and turbulence conditions. These holograms were based on natural objects, serving as training and testing data for the neural network. The results demonstrate that TWC-Swin effectively restores holographic images even under low spatial coherence and arbitrary turbulence, surpassing traditional convolutional network-based methods. Furthermore, the method reportedly exhibits strong generalization capabilities, extending its application to unseen scenes not included in the training data.
CAPTION
Qualitative analysis of performance across varying intensities of oceanic and atmospheric turbulence. The network trained with coherence as physical prior information can effectively overcome the impact of oceanic and atmospheric turbulence on imaging and improve image quality.
CREDIT
Credit: X. Tong et al., doi 10.1117/1.AP.5.6.066003.
Qualitative analysis of performance across varying intensities of oceanic and atmospheric turbulence. The network trained with coherence as physical prior information can effectively overcome the impact of oceanic and atmospheric turbulence on imaging and improve image quality.
CREDIT
Credit: X. Tong et al., doi 10.1117/1.AP.5.6.066003.
This research breaks new ground in addressing image degradation in holographic imaging across diverse scenes. By integrating physical principles into deep learning, the study sheds light on a successful synergy between optics and computer science. As the future unfolds, this work paves the way for enhanced holographic imaging, empowering us to see clearly through the turbulence.
A new Antarctic ice sheet modeling study from scientists at UC San Diego’s Scripps Institution of Oceanography suggests that meltwater flowing out to sea from beneath Antarctic glaciers is making them lose ice faster.
The model’s simulations suggest this effect is large enough to make a meaningful contribution to global sea-level rise under high greenhouse gas emissions scenarios.
The extra ice loss caused by this meltwater flowing out to sea from beneath Antarctic glaciers is not currently accounted for in the models generating major sea-level rise projections, such as those of the Intergovernmental Panel on Climate Change (IPCC). If this process turns out to be an important driver of ice loss across the entire Antarctic ice sheet, it could mean current projections underestimate the pace of global sea-level rise in decades to come.
“Knowing when and how much global sea-level will rise is critical to the welfare of coastal communities,” said Tyler Pelle, the study’s lead author and a postdoctoral researcher at Scripps. “Millions of people live in low-lying coastal zones and we can’t adequately prepare our communities without accurate sea-level rise projections.”
The study, published October 27 in Science Advances and funded by the National Science Foundation (NSF), NASA, and the Cecil H. and the Ida M. Green Foundation for Earth Sciences at the Institute of Geophysics and Planetary Physics at Scripps, modeled the retreat of two glaciers in East Antarctica through the year 2300 under different emissions scenarios and projected their contributions to sea-level rise. Unlike previous Antarctic ice sheet models, this one included the influence of this flow of meltwater from beneath glaciers out to sea, which is known as subglacial discharge.
The two glaciers the study focused on, named Denman and Scott, together hold enough ice to cause nearly 1.5 meters (5 feet) of sea-level rise. In a high emissions scenario (IPCC’s SSP5-8.5 scenario, which assumes no new climate policy and features 20% higher CO2 emissions by 2100), the model found that subglacial discharge increased the sea-level rise contribution of these glaciers by 15.7%, from 19 millimeters (0.74 inches) to 22 millimeters (0.86 inches) by the year 2300.
These glaciers, which are right next to each other, sit atop a continental trench that is more than two miles deep; once their retreat reaches the trench’s steep slope, their contribution to sea-level rise is expected to accelerate dramatically. With the added influence of subglacial discharge, the model found that the glaciers retreated past this threshold about 25 years earlier than they did without it.
“I think this paper is a wake up call for the modeling community. It shows you can’t accurately model these systems without taking this process into account,” said Jamin Greenbaum, co-author of the study and a researcher at Scripps’ Institute of Geophysics and Planetary Physics.
A key takeaway, beyond the understudied role of subglacial discharge in accelerating sea-level rise, is the importance of what humanity does in the coming decades to rein in greenhouse gas emissions, said Greenbaum. The low emissions scenario runs of the model did not show the glaciers retreating all the way into the trench and avoided the resulting runaway contributions to sea-level rise.
“If there is a doomsday story here it isn’t subglacial discharge,” said Greenbaum. “The real doomsday story is still emissions and humanity is still the one with its finger on the button.”
In Antarctica, subglacial meltwater is generated from melting that occurs where the ice sits on continental bedrock. The main sources of the heat melting the ice in contact with the ground are friction from the ice grinding across the bedrock and geothermal heat from Earth’s interior permeating up through the crust.
Prior research suggested that subglacial meltwater is a common feature of glaciers around the world and that it is present under severalother massive Antarctic glaciers, including the infamousThwaites Glacier in West Antarctica.
When subglacial discharge flows out to sea it is thought to accelerate melting of the glacier’s ice shelf – a long floating tongue of ice that extends out to sea beyond the last part of the glacier that is still in contact with solid ground (known as the grounding line). Subglacial discharge is thought to speed up ice shelf melting and glacial retreat by causing ocean mixing that stirs in additional ocean heat within the cavity beneath a glacier's floating ice shelf. This enhanced ice shelf melting then causes the upstream glacier to accelerate, which can drive sea level rise.
The notion that subglacial discharge causes additional ice shelf melting is widely accepted in the scientific community, said Greenbaum. But it hasn’t been included in sea-level rise projections because many researchers weren’t sure if the process’ effect was sufficiently large to increase sea-level rise, mainly because its effects are localized around the glacier’s ice shelf.
Pelle said subglacial discharge came onto his radar in 2021 when he and his colleagues observed that East Antarctica’s Denman Glacier’s ice shelf was melting faster than expected given local ocean temperatures. Puzzlingly, Denman’s neighbor Scott Glacier’s ice shelf was melting much more slowly despite virtually identical ocean conditions.
To test whether subglacial discharge could reconcile the melt rates seen at the Denman and Scott ice shelves, as well as whether subglacial meltwater might accelerate sea-level rise, the team combined models for three different environments: the ice sheet, the space between the ice sheet and bedrock, and the ocean.
Once the researchers married the three models into one they ran a series of projections up to 2300 using a NASA supercomputer.
The projections featured three main scenarios: a control that featured no additional ocean warming, a low emissions pathway (SSP1-2.6), and a high emissions pathway (SSP5-8.5). For each scenario, the researchers created projections with and without the effect of present-day levels of subglacial discharge.
The model’s simulations revealed that adding in subglacial discharge reconciled the melt rates seen at Denman and Scott Glaciers. As for why Scott Glacier was melting so much slower than Denman, Pelle said the model showed that “a strong subglacial discharge channel drained across the Denman Glacier grounding line, while a weaker discharge channel drained across the Scott Glacier grounding line.” The strength of the discharge channel at Denman, Pelle explained, was behind its speedy melt.
For the control and low-emissions model runs the contributions to sea-level rise were close to zero or even slightly negative with or without subglacial discharge at 2300. But in a high emissions scenario, the model found that subglacial discharge increased the sea-level rise contribution of these glaciers from 19 millimeters (0.74 inches) to 22 millimeters (0.86 inches) in 2300.
In the high emissions scenario that included subglacial discharge, Denman and Scott Glaciers retreated into the two-mile-deep trench beneath them by 2240, about 25 years earlier than they did in the model runs without subglacial discharge. Once the grounding lines of the Denman and Scott Glaciers retreat past the lip of this trench their yearly sea-level rise contribution explodes, reaching a peak of 0.33 millimeters (0.01 inches) per year – roughly half of the present-day annual sea-level rise contribution of the entire Antarctic ice sheet.
Pelle said the trench’s steep slope is behind this explosive increase in sea-level rise contribution. As the glacier retreats down slope, its ice shelf begins losing thicker and thicker slabs of ice from its leading edge. This process of ice loss quickly outpaces ice accumulation at the ice sheet’s interior, causing further glacial retreat. Researchers refer to this process as "Marine Ice Sheet Instability," and it can promote explosive ice loss from glaciers like Denman and Scott.
Researchers refer to topography such as the trench beneath Denman and Scott Glaciers as a retrograde slope and worry that it creates a positive feedback loop by which glacial retreat begets more retreat. Large areas of the West Antarctic Ice Sheet, such as Thwaites Glacier, also have retrograde slopes that, while not as dramatic as the Denman-Scott trench, contribute to fears of broader ice sheet instability.
“Subglacial meltwater has been inferred beneath most if not all Antarctic glaciers, including Thwaites, Pine Island, and Totten glaciers,” said Pelle. “All these glaciers are retreating and contributing to sea-level rise and we are showing that subglacial discharge could be accelerating their retreat. It’s urgent that we model these other glaciers so we can get a handle on the magnitude of the effect subglacial discharge is having.”
The researchers behind this study are doing just that. Pelle said they are in the process of submitting a research proposal to extend their new model to the entire Antarctic ice sheet.
Future iterations of the model may also attempt to couple the subglacial environment with the ice sheet and ocean models so that the amount of subglacial meltwater dynamically responds to these other factors. Greenbaum said that the current version of their model kept the amount of subglacial meltwater constant throughout the model runs, and that making it respond dynamically to the surrounding environment would likely make the model more true to life.
“This also means that our results are probably a conservative estimate of the effect of subglacial discharge,” said Greenbaum. “That said, we can’t yet say how much sea-level rise will be accelerated by this process – hopefully it’s not too much.”
Part of Greenbaum’s upcoming fieldwork in Antarctica, supported by NSF and NASA, aims to directly investigate the impacts of subglacial meltwater in both the East and West Antarctic ice sheets. In collaboration with the Australian Antarctic Division and the Korea Polar Research Institute, Greenbaum and his collaborators will be visiting the ice shelves of Denman and Thwaites Glaciers in East and West Antarctica, respectively, looking for direct evidence that subglacial freshwater is discharging into the ocean beneath the glaciers’ ice shelves and contributing to warming.
In addition to Pelle and Greenbaum, the study was co-authored by Christine Dow of the University of Waterloo, Adrian Jenkins of Northumbria University, and Mathieu Morlighem of Dartmouth College.
ITHACA, N.Y. – More than merely cracks in the ice, crevasses play an important role in circulating seawater beneath Antarctic ice shelves, potentially influencing their stability, finds Cornell University-led research based on a first-of-its-kind exploration by an underwater robot.
The remotely operated Icefin robot’s climb up and down a crevasse in the base of the Ross Ice Shelf produced the first 3D measurements of ocean conditions near where it meets the coastline, a critical juncture known as the grounding zone.
The robotic survey revealed a new circulation pattern – a jet funneling water sideways through the crevasse – in addition to rising and sinking currents, and diverse ice formations shaped by shifting flows and temperatures. Those details will improve modeling of ice shelf melting and freezing rates at grounding zones, where few direct observations exist, and of their potential contribution to global sea-level rise.
“Crevasses move water along the coastline of an ice shelf to an extent previously unknown, and in a way models did not predict,” said Peter Washam, a polar oceanographer and research scientist at Cornell University. “The ocean takes advantage of these features, and you can ventilate the ice shelf cavity through them.”
Washam is the lead author of “Direct Observations of Melting, Freezing and Ocean Circulation in an Ice Shelf Basal Crevasse,” published in Science Advances.
The scientists in late 2019 deployed the Icefin vehicle – roughly 12 feet long and less than 10 inches around – on a tether down a 1,900-foot borehole drilled with hot water, near where Antarctica’s largest ice shelf meets the Kamb Ice Stream. Such so-called grounding zones are key to controlling the balance of ice sheets, and the places where changing ocean conditions can have the most impact.
On the team’s last of three dives, Matthew Meister, a senior research engineer, drove Icefin into one of five crevasses found near the borehole. Equipped with thrusters, cameras, sonar and sensors for measuring water temperature, pressure and salinity, the vehicle climbed nearly 150 feet up one slope and descended the other.
The survey detailed changing ice patterns as the crevasse narrowed, with scalloped indentations giving way to vertical runnels, then green-tinted marine ice and stalactites. Melting at the crevasse base and salt rejection from freezing near the top moved water up and down around the horizontal jet, driving uneven melting and freezing on the two sides, with more melting along the lower downstream wall.
“Each feature reveals a different type of circulation or relationship of the ocean temperature to freezing,” Washam said. “Seeing so many different features within a crevasse, so many changes in the circulation, was surprising.”
The researchers said the findings highlight crevasses’ potential to transport changing ocean conditions – warmer or colder – through an ice shelf’s most vulnerable region.
“If water heats up or cools off, it can move around in the back of the ice shelf quite vigorously, and crevasses are one of the means by which that happens,” Washam said. “When it comes to projecting sea-level rise, that’s important to have in the models.”
The research was funded by Project RISE UP (Ross Ice Shelf and Europa Underwater Probe), part of NASA’s Planetary Science and Technology from Analog Research program, with logistical support provided by the National Science Foundation through the U.S. Antarctic Program. It was facilitated by the New Zealand Antarctic Research Institute, Aotearoa New Zealand Antarctic Science Platform and the Victoria University of Wellington Hot Water Drilling initiative.
JOURNAL
Science Advances
ARTICLE TITLE
Direct Observations of Melting, Freezing and Ocean Circulation in an Ice Shelf Basal Crevasse
ARTICLE PUBLICATION DATE
27-Oct-2023
UCLA researcher finds first proof of menopause in wild chimpanzees
A study of the Ngogo community in Uganda shows humans aren’t the only primates with long post-fertile life stage
Female chimpanzees in Uganda’s Ngogo community experienced a menopausal transition similar to women.
Fertility among chimpanzees studied declined after age 30, and no births were observed after age 50.
The data can help researchers better understand why menopause and post-fertile survival occur in nature and how it evolved in the human species.
A team of researchers studying the Ngogo community of wild chimpanzees in western Uganda’s Kibale National Park for two decades has published a report in Science showing that females in this population can experience menopause and postreproductive survival.
Prior to the study, “Demographic and hormonal evidence for menopause in wild chimpanzees,” these traits had only been found among mammals in a few species of toothed whales, and among primates — only in humans. These new demographic and physiological data can help researchers better understand why menopause and post-fertile survival occur in nature, and how it evolved in the human species.
“In societies around the world, women past their childbearing years play important roles, both economically and as wise advisors and caregivers,” said Brian Wood, UCLA associate professor of anthropology. “How this life history evolved in humans is a fascinating yet challenging puzzle.”
Wood, first author of the paper, worked closely with Kevin Langergraber from Arizona State University, Jacob Negrey of University of Arizona, and Ngogo Chimpanzee Project founders and co-directors John Mitani and David Watts.
“The (study) results show that under certain ecological conditions, menopause and post-fertile survival can emerge within a social system that’s quite unlike our own and includes no grandparental support,” Wood said, referring to the grandmother hypothesis.
That hypothesis, which has been used to explain the existence of human postmenopausal survival, proposes that females in their postreproductive years may be able to pass on more of their genes by helping to raise the birth rates of their own children or by caring directly for grandchildren, thereby increasing grandchildren’s odds of survival. And indeed, several studies of human grandmothers have found these positive effects. But chimpanzees have very different living arrangements than humans. Older female chimpanzees typically do not live near their daughters or provide care for grandchildren, yet females at Ngogo often live past their childbearing years.
While substantial postreproductive life spans have not previously been observed in other long-term studies of wild chimpanzees, they have sometimes been seen in chimpanzees and other primates in captivity, who receive good nutrition and medical care. This raises the possibility that the postreproductive life spans of female Ngogo chimpanzees may be a temporary response to unusually favorable ecological conditions, as this population enjoys a stable and abundant food supply and low levels of predation. Another possibility, however, is that postreproductive life spans are actually an evolved, species-typical trait in chimpanzees but have not been observed in other chimpanzee populations because of the recent negative impacts of humans.
“Chimpanzees are extremely susceptible to dying from diseases that originate in humans and to which they have little natural immunity,” Langergraber said. “Chimpanzee researchers, including us at Ngogo, have learned over the years how devastating these disease outbreaks can be to chimpanzee populations, and how to reduce their chances of happening.”
An extraordinary effort
The team of researchers examined mortality and fertility rates of 185 female chimpanzees from demographic data collected from 1995 to 2016. They calculated the fraction of adult life spent in a postreproductive state for all the observed females and measured hormone levels in urine samples from 66 females of varying reproductive statuses and ages, ranging from 14 to 67 years.
Thousands of hours of fieldwork at Ngogo were needed to collect the observations and samples needed for this study. Hormone samples were analyzed by Tobias Deschner and Melissa Emery Thompson.
“This study is the result of an extraordinary amount of effort,” Negrey said. “It’s only because our team has spent decades monitoring these chimpanzees that we can be confident some females live long after they’ve stopped reproducing. We also spent thousands of hours in the forest to collect urine samples from these chimpanzees with which to study hormonal signals of menopause.”
The researchers measured hormone levels associated with human menopause, which include increasing levels of follicle-stimulating hormone and luteinizing hormone, as well as decreasing levels of ovarian steroid hormones including estrogens and progestins.
As with other chimpanzee populations and humans, fertility in the chimpanzees studied declined after age 30, with no births observed after age 50. The hormone data showed that the Ngogo females experienced a menopausal transition similar to that of humans, beginning around age 50.
Also like humans, it was not unusual for these female chimpanzees to live past 50. A female who reached adulthood at age 14 was postreproductive for about one-fifth of her adult life, about half as long as a human hunter-gatherer.
“We now know that menopause and post-fertile survival arise across a broader range of species and socio-ecological conditions than formerly appreciated, providing a solid basis for considering the roles that improved diets and lowered risks of predation would have played in human life history evolution,” Wood said.
The researchers say that it will also be critical to track the behavior of older chimpanzees and observe how they interact with and influence other group members.
“To allow such work, it is essential to support the long-term study of primates in the wild,” Wood said.
