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)
Tuesday, October 03, 2023
Migratory birds can be taught to adjust to climate change, study shows
European Pied Flycatcher in Sweden. Credit: Wikipedia
One result of climate change is that spring is arriving earlier. However, migratory birds are not keeping up with these developments and arrive too late for the peak in food availability when it is time for breeding. By getting the birds to fly a little further north, researchers in Lund, Sweden, and the Netherlands have observed that these birds can give their chicks a better start in life.
Global warming is causing problems for birds in Sweden and elsewhere. Warmer springs mean that caterpillars hatch, grow and pupate earlier compared with just a few decades ago. This has consequences for birds that cannot eat caterpillars that have entered the pupal stage.
Therefore, when the food supply runs out at an ever earlier time in the spring, more and more chicks starve during the breeding season. This is a big problem for migratory birds that spend winters in Africa, as they do not know how early spring arrives in Sweden. Could the problem be solved if the migratory birds simply came home and started breeding earlier?
"It seems that our non-migratory birds are doing this to a certain extent. But, of course, they are present and can feel how early spring will come. We thought that perhaps the migratory birds could fly further north until they find a place with suitable well-developed caterpillars," says Jan-Åke Nilsson, biology researcher at Lund University in Sweden.
To test this in practice, the researchers decided to help some pied flycatchers along the way. The research is published in the journal Nature Ecology & Evolution.
The biologists caught pied flycatchers that had arrived prior to breeding in the Netherlands. The birds were then driven during the night to Vombs Fure, an area of pine forest outside Lund in Skåne, where they were released. The peak of caterpillar availability in Skåne is about two weeks later than in the Netherlands—a distance of around 600 kilometers that a pied flycatcher could cover in just two nights.
"The birds that were given a lift from the Netherlands to Skåne synchronized very well with the food peak. As they started to breed about 10 days earlier the 'Swedish' pied flycatchers they had a dramatically better breeding success than the Swedish ones as well as a better success than the pied flycatchers that remained in the Netherlands," says Jan-Åke Nilsson.
In addition, it was shown that the chicks of the Dutch pied flycatchers that had received migration assistance did not stop in the Netherlands when they returned after their first spring migration. Instead, they continued on to the area of pine forest outside Lund where they were born.
Furthermore, they arrived earlier than the Swedish pied flycatchers and thereby had more well-fed chicks at Vombs Fure the year after the researchers gave the pied flycatchers a helping hand to find Skåne.
"The number of small birds, particularly migratory birds, has decreased drastically throughout Europe. By flying a little further north, these birds, at least in principle, could synchronize with their food resources and there is hope that robust populations of small birds can be maintained, even though springs are arriving ever earlier," concludes Jan-Åke Nilsson.
More information: Koosje P. Lamers et al, Adaptation to climate change through dispersal and inherited timing in an avian migrant, Nature Ecology & Evolution (2023). DOI: 10.1038/s41559-023-02191-w
Clothes that are produced quickly and just as quickly go out of style and into the trash bin can have dire effects on the environment, polluting the air with carbon and choking landfills with chemicals that can seep into the water supply.
A Penn State Smeal College of Business-led team of researchers found a new business model may address the issue of overconsumption without burdening companies operating within the fiercely competitive fashion industry.
The researchers found that consumers are willing to pay more money for clothes they can customize and keep the items longer. The findings, published in the Journal of Operations Management, suggest that clothing companies that adopt a mass customization model can remain profitable while decreasing the fashion industry's environmental impacts.
"What we were asking is: How do we find a way to provide product variety while not suffering significant cost on initial manufacturing expenses?" said corresponding author Dan Guide, Smeal Chaired Professor of Operations and Supply Chain Management. "The big idea is that we'd like for people to stop disposing of stuff as fast as they do."
Aydin Alptekinoglu, professor of operations and supply chain management and Robert G. Schwartz University Endowed Fellow in Business Administration, served as first author on the paper.
"We hypothesized and showed that providing customization to cater for individual consumer tastes but at a mass scale—the idea of mass customization applied to fashion—might help delay the eventual disposal," Alptekinoglu said. "In fact, we think mass customization can be the basis for a new business model in fashion that is more sustainable and more profitable."
According to Guide, fast fashion refers to how the fashion industry often produces clothes made of inexpensive, plastic-based synthetic materials called polymers. Because the clothes are cheap and tend to wear out quickly, consumers are more likely to throw them out and buy new instead of attempting to repair them. The clothes typically end up in landfills and the chemicals that make up these cheap polymers can infiltrate the water supply.
"The big problem with these artificial fibers is that they are a complex blend of polymers," Guide said. "They're really many different types of plastic, which we tend to do a lousy job of sorting, so these polymers become too complicated to recycle and the plastics can, for example, end up seeping into the water supply."
Recycling is often not an option either because the polymers are often too complex to efficiently recover, added Guide.
Making business sense
According to Guide, by proving people will pay more for their personalized clothes, businesses can compensate by selling fewer clothes for more money, rather than selling more units of disposable clothing for less money.
No business will adopt a practice that will hurt its ability to compete, or hurt their investors, said Guide.
"Our business school and, in particular, my supply chain department does a lot of work with companies," Guide said. "So, when we talk to managers and engineers, I would feel very comfortable going into those businesses and those plants and telling them this is a way that you can make money while still doing good. I love that message for companies."
According to the researchers, the solution is also practical because the technology currently exists to allow many people to personalize their products online. For example, customers can upload their pictures to a website to review different sunglass styles, or virtually try on clothes.
Equally important, flexible manufacturing technologies exist to support such product customization at a mass scale. For example, 3D printing and various other automation technologies make one-of-a-kind, serial production possible. Alptekinoglu said he expects that the economics of such technologies, which are constantly improving, will naturally point the fashion industry toward mass customization.
Studies
To test the business model, the researchers conducted a pre-test, followed by two studies to investigate consumers' reactions to varying degrees of the mass customization of T-shirts.
In the first study, 237 undergraduate students were randomly assigned to participate in person, where the team examined the effects of four customers' involvement points—design, fabrication and use—on their willingness to pay for and hold onto the T-shirts. The customers could opt for ready-made T-shirts produced by the firm, or what the researchers termed "use."
Alternatively, they could personalize their T-shirt by selecting from a range of existing colors and images provided by the firm, or "assembly." For more extensive customization, customers could create their own custom color and select from the firm's library of pre-existing images, or "fabrication." For the ultimate level of personalization, called "design," customers had the freedom to design a completely unique T-shirt by crafting their own custom color and image.
In the second study, the focus shifted to exploring different approaches to a single point of customer involvement in mass customization. The team recruited 501 U.S. participants, randomly assigning them to five different groups representing distinct customization conditions. The researchers specifically investigated the influence of providing sample images in the design condition on how much the participants would pay for and how long they would keep the customized products.
By randomly assigning participants to one of these conditions, the researchers were able to test how different aspects of customer involvement affect the overall mass customization experience and its consequences.
Future work
According to the researchers, there is still more work to be done.
"While the basic idea is applicable to many other industries with significant interest in mass customization, like auto and furniture, the current supply chain structures and consumer behavioral dynamics in those industries can be vastly different," Alptekinoglu said. "So, expanding to other product categories while respecting those differences might be very useful."
One of the limitations of the study is that the researchers recruited mostly students from western cultures, so a next research step would be to investigate if there are similar customer behaviors in other countries and cultures.
Guide said another action step would be more outreach to move this research from the laboratory and into real life.
"I'm used to taking what I'm doing and bringing it to a company to get them to tell me what they think about the concept," Guide said. "I'd like to see us make an effort to get this information out to these managers."
Guide said that the research team's unique interdisciplinary approach—in this case, joining supply chain with marketing scientists together—will be helpful in investigating solutions to fast fashion's environmental impact.
"We have a team who are used to working with each other," Guide said. "And each member knows an area—such as behavioral marketing and analytical modeling—and that interdisciplinary approach helps us look at the question of sustainability that is solution-based, that businesses will be willing to adopt."
More information: Aydin Alptekinoglu et al, Can mass customization slow fast fashion down? The impact on time‐to‐disposal and willingness‐to‐pay, Journal of Operations Management (2023). DOI: 10.1002/joom.1255
Charged ions interacting with the Earth’s magnetic field often create auroras near the planet’s poles. The aurora australis or the “southern lights,” are captured here by a NASA satellite. Credit: NASA Earth Observatory.
The iron atoms that make up the Earth's solid inner core are tightly jammed together by astronomically high pressures—the highest on the planet.
But even here, there's space for wiggle room, researchers have found.
A study led by The University of Texas at Austin and collaborators in China found that certain groupings of iron atoms in the Earth's inner core are able to move about rapidly, changing their places in a split second while maintaining the underlying metallic structure of the iron—a type of movement known as "collective motion" that's akin to dinner guests changing seats at a table.
The results, which were informed by laboratory experiments and theoretical models, indicate that atoms in the inner core move around much more than previously thought.
The results could help explain numerous intriguing properties of the inner core that have long vexed scientists, as well as help shed light on the role the inner core plays in powering Earth's geodynamo—the elusive process that generates the planet's magnetic field.
"Now, we know about the fundamental mechanism that will help us with understanding the dynamic processes and evolution of the Earth's inner core," said Jung-Fu Lin, a professor at the UT Jackson School of Geosciences and one of the study's lead authors.
It's impossible for scientists to directly sample the Earth's inner core because of its extremely high temperatures and pressures. So, Lin and collaborators re-created it in miniature in the lab by taking a small iron plate and shooting it with a fast-moving projectile. The temperature, pressure and velocity data collected during the experiment was then put into a machine-learning computer model of atoms in the inner core.
Scientists think that iron atoms in the inner core are arranged in a repeating hexagonal configuration. According to Lin, most computer models portraying the lattice dynamics of iron in the inner core show only a small number of atoms—usually fewer than a hundred. But using an AI algorithm, the researchers were able to significantly beef up the atomic environment, creating a "supercell" of about 30,000 atoms to more reliably predict iron's properties.
At this supercell scale, the scientists observed groups of atoms moving about, changing places while still maintaining the overall hexagonal structure.
The researchers said that the atomic movement could explain why seismic measurements of the inner core show an environment that's much softer and malleable than would be expected at such pressures, said co-lead author Youjun Zhang, a professor at Sichuan University.
A model of iron atoms on the move in Earth's inner core. Credit: Youjun Zhang et al.
"Seismologists have found that the center of the Earth, called the inner core, is surprisingly soft, kind of like how butter is soft in your kitchen," he said. "The big discovery that we've found is that solid iron becomes surprisingly soft deep inside the Earth because its atoms can move much more than we ever imagined. This increased movement makes the inner core less rigid, weaker against shear forces."
The researchers said that searching for an answer to explain the "surprisingly soft" physical properties reflected in the seismic data is what motivated their research.
About half of the geodynamo energy that generates the Earth's magnetic field can be attributed to the inner core, according to the researchers, with the outer core making up the rest. The new insight on inner core activity at the atomic scale can help inform future research on how energy and heat are generated in the inner core, how it relates to the dynamics of the outer core, and how they work together to generate the planet's magnetic field that is a key ingredient for a habitable planet.
More information: Youjun Zhang et al, Collective motion in hcp-Fe at Earth's inner core conditions, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2309952120
The CAS-ESM team discussed the simulation results of fully coupled atmospheric CO2seasonal variations while examining visualizations on the suspended dome screen at the Earth System Numerical Simulation Facility (EarthLab). Credit: Guoqiang Li
The Chinese Academy of Sciences Earth System Model (CAS-ESM2.0), a sophisticated Earth modeling tool, has achieved a major breakthrough in fully coupled atmospheric CO2 simulation, as revealed in Advances in Atmospheric Sciences.
The study was conducted by researchers from the Institute of Atmospheric Physics of the Chinese Academy of Sciences, Beijing Normal University and Stony Brook University.
Their findings highlight CAS-ESM2.0's exceptional capability in two-way coupling of terrestrial and marine carbon cycles, along with atmospheric CO2, enabling accurate spatiotemporal assessments of atmospheric CO2 changes.
Atmospheric CO2, a pivotal greenhouse gas, has surged since the Industrial Revolution, significantly affecting both the global climate, leading to warming through the greenhouse effect, and ecosystems by enhancing plant photosynthesis. It remains central to worldwide climate and environmental research.
Earth system models play a vital role in studying atmospheric CO2 concentration changes and their complex interactions with climate across different spatiotemporal scales. Achieving full coupling of atmospheric CO2 in these models has long been a challenge, particularly in emissions-driven simulations, where CO2 interacts with land and ocean carbon cycles. This complexity presents numerous challenges and uncertainties.
CAS-ESM2 is capable of reasonably simulating the increasing trend of atmospheric CO2 from 1850 to 2014, as well as the response of land and ocean net carbon fluxes. Credit: Jiawen Zhu and GPVis Visualization Team
Over several decades, CAS-ESM has undergone continuous development, culminating in the release of CAS-ESM2.0. This latest version has completed the sixth phase of the Coupled Model Intercomparison Project (CMIP6) Diagnosis, Evaluation, and Characterization of Klima (DECK) simulations (concentration-driven runs) and submitted the results to CMIP6.
The team's subsequent efforts focused on enhancing CAS-ESM2.0 to achieve two-way coupling among atmospheric CO2, the physical climate system, and the carbon cycle in land and ocean. This breakthrough empowers CAS-ESM2.0 to simulate CO2-carbon-climate interactions and autonomously calculate atmospheric CO2 concentrations.
Leveraging CAS-ESM2.0's capabilities, the researchers conducted a coupled carbon-climate simulation in alignment with CMIP6's historical emissions-driven experiment proposal. The results are remarkable, with CAS-ESM2.0 demonstrating excellent agreement with observations, accurately reproducing the rising trend of annual CO2 levels from 1850 to 2014 and capturing the seasonal CO2 cycle.
CAS-ESM's potential applications, given its ability to simulate CO2-carbon-climate interactions, are manifold. It offers a valuable tool for investigating scientific issues related to carbon-climate interactions, enabling quantification of model biases associated with specific processes, such as fire and vegetation dynamics, and revealing the underlying mechanisms.
Furthermore, CAS-ESM holds promise in supporting China's goal of carbon neutrality. By employing CAS-ESM to assess net carbon fluxes at each stage of the carbon-neutrality journey, policymakers can receive invaluable insights to refine strategies on carbon neutrality.
More information: Jiawen Zhu et al, CAS-ESM2.0 Successfully Reproduces Historical Atmospheric CO2 in a Coupled Carbon-Climate Simulation, Advances in Atmospheric Sciences (2023). DOI: 10.1007/s00376-023-3172-9
With the help of advanced sonar, the researchers can observe the water column and, in this case, the gas bubbles rising from the ocean floor to the surface. The sonar also penetrates the bottom sediments, which provides important information about the properties of the seabed and, for example, whether there is gas hidden in the sediments. Credit: Christian Stranne
During a research expedition led by Linnaeus University and Stockholm University to the deepest parts of the Baltic Sea in the Landsort Deep researchers recently discovered an area with extensive emissions of the powerful greenhouse gas methane from the bottom sediments.
The area where the methane leak was discovered is located in the Landsort Deep (Landsortsdjupet), about 30 kilometers southeast of the coastal town Nynäshamn. Christian Stranne, associate professor of marine geophysics at Stockholm University, is surprised by the discovery.
"We know that methane gas can bubble out from shallow coastal seabeds in the Baltic Sea, but I have never seen such an intense bubble release before and definitely not from such a deep area," says Christian Stranne.
A poorly understood phenomenon
The research project aims to expand knowledge about methane and its sources and sinks in the oxygen-free environments in the deeper parts of the Baltic Sea. The project is led by Marcelo Ketzer, professor of environmental science at Linnaeus University.
"Knowledge about the factors that control how much methane is produced in these deeper areas and where the methane goes is limited. How does the system react to, for example, eutrophication or a warmer climate? I knew from one of my previous projects that the methane levels in the sediments in this area are higher than elsewhere in the Baltic Sea, but I never expected methane to bubble out into the sea in this way," says Marcelo Ketzer.
The researchers determined the area's extent to be about 20 square kilometers (equivalent to almost 4,000 football pitches) and it lies at a depth of around 400 meters. During the expedition, a large number of sediment cores and water samples were collected, and now the researchers hope that further analyses will be able to provide answers to why so much methane gas is released from this specific area.
"We already have a pretty good idea of why it looks the way it does. The size of the sediment grains in the area and the form of the seafloorgive us an indication. It seems like deep ocean currents are causing sediments to accumulate in this particular area, but we need to do more detailed analyses before we can say anything definitive," says Marcelo Ketzer.
The bubbles rise to the surface of the sea
Another interesting discovery made during the expedition concerns how high up through the water column the methane bubbles rise.
"At the depths we are working with here, you can expect the methane bubbles to reach at most perhaps 150–200 meters from the seabed. The methane in the bubbles dissolves in the ocean and therefore they usually gradually decrease in size as they rise towards the sea surface," says Christian Stranne.
"It is actually quite a complicated balance between pressure effects and diffusion of gases that together determine how size and gas composition develop in a bubble, but the net effect for smaller bubbles is that they lose both size and rise velocity with increased distance from the bottom."
To the researchers' great surprise, they could see some bubbles rising to 370 meters from the ocean floor.
"Bubbles from deep-sea sediments (around a thousand meters and deeper) can rise significantly higher due to a coating of 'frozen methane' that forms around the bubble," says Stranne.
"This summer I participated in a French expedition to the Amazon outlet where we observed bubbles rising up to 700 meters above the seabed. But I don't know of any study where such persistent bubbles have been observed at these depths—it could be a new world record, and it could force us to re-evaluate the role of deep basins in the Baltic Sea, in terms of contribution to the surface water methane content."
Oxygen-free bottoms mighty be the explanation
The researchers have so far not been able to find out exactly how high the bubbles reach. From the sonar, they can see bubbles to at least 40 meters from the sea surface, but it may well be that some bubbles reach significantly higher than that. One of the explanations may be that the bubbles are unusually large, but the researchers have an alternative explanation that they consider more likely.
"Rather, we believe that it is linked to the oxygen-free conditions in the deep water of the Baltic Sea. If there is no oxygen, the levels of dissolved methane in the ocean can be relatively high, which in turn leads to the bubbles not losing methane as quickly. The bubbles are thus kept more intact in this environment, which means that methane transport towards the sea surface becomes more efficient," says Stranne.
"It is a hypothesis that we are currently investigating and if it proves to be correct, it could have consequences—if the oxygen conditions in the Baltic Sea deteriorate further, it would probably lead to a greater transport of methane from the deeper parts of the Baltic Sea, but it remains to be investigated how much may leak into the atmosphere."
Marcelo Ketzer and Christian Stranne believe that methane gas emissions similar to those discovered in the Landsort Deep may also occur in other places in the Baltic Sea.
"Now we know what to look for and we look forward to testing this model in other areas of the Baltic Sea with similar geological conditions. There are potentially another half dozen places to explore," Marcelo Ketzer adds.
Artist's rendition of the upcoming NASA Solar Cruiser mission due to launch in February 2025, an example of the type of solar sail being developed for this most recent study. Credit: NASA
A recent study submitted to Acta Astronautica and currently available on the arXiv preprint server explores the potential for using aerographite solar sails for traveling to Mars and interstellar space, which could dramatically reduce both the time and fuel required for such missions.
This study comes while ongoing research into the use of solar sails is being conducted by a plethora of organizations along with the successful LightSail2 mission by The Planetary Society, and holds the potential to develop faster and more efficient propulsion systems for long-term space missions.
"Solar sail propulsion has the potential for rapid delivery of small payloads (sub-kilogram) throughout the solar system," Dr. René Heller, who is an astrophysicist at the Max Planck Institute for solar system Research and a co-author on the study, tells Universe Today. "Compared to conventional chemical propulsion, which can bring hundreds of tons of payload to low-Earth orbit and deliver a large fraction of that to the moon, Mars, and beyond, this sounds ridiculously small. But the key value of solar sail technology is speed."
Unlike conventional rockets, which rely on fuel in the form of a combustion of chemicals to exert an external force out the back of the spacecraft, solar sails don't require fuel. Instead, they use sunlight for their propulsion mechanism, as the giant sails catch solar photons much like wind sails catching the wind when traveling across water. The longer the solar sails are deployed, the more solar photons are captured, which gradually increases the speed of the spacecraft.
For the study, the researchers conducted simulations on how fast a solar sail made of aerographite with a mass up to 1 kilogram (2.2 pounds), including 720 grams of aerographite with a cross-sectional area of 104 square meters, could reach Mars and the interstellar medium, also called the heliopause, using two trajectories from Earth known as direct outward transfer and inward transfer methods, respectively.
The direct outward transfer method for both the trip to Mars and the heliopause involved the solar sail both deploying and departing directly from a polar orbit around the Earth. The researchers determined that Mars being in opposition (directly opposite Earth from the sun) at the time of solar sail deployment and departure from Earth would yield the best results for both velocity and travel time.
This same polar orbit deployment and departure was also used for the heliopause trajectory, as well. For the inward transfer method, the solar sail would be delivered to approximately 0.6 astronomical units (AU) from the sun via traditional chemical rockets, where the solar sail would deploy and begin its journey to either Mars or the heliopause. But how does an aerographite solar sail make this journey more feasible?
Image taken by The Planetary Society’s LightSail 2 on 25 November 2019 during its mission orbiting the Earth. The curved appearance of the sails is from the spacecraft’s 185-degree fisheye camera lens, and the image was processed with color-correction along with removal of parts of the distortion. Credit: The Planetary Society
"With its low density of 0.18 kilograms per cubic meter, aerographite undercuts all conventional solar sail materials," Julius Karlapp, who is a Research Assistant at the Dresden University of Technology and lead author of the study, tells Universe Today. "Compared to Mylar (a metallized polyester foil), for example, the density is four orders of magnitude smaller. Assuming that the thrust developed by a solar sail is directly dependent on the mass of the sail, the resulting thrust force is much higher. In addition to the acceleration advantage, the mechanical properties of aerographite are amazing."
Through these simulations, the researchers found the direct outward transfer method and inward transfer method resulted in the solar sail reaching Mars in 26 days and 126 days, respectively, with the first 103 days being the travel time from Earth to the deployment point at 0.6 AU.
For the journey to the heliopause, both methods resulted in 5.3 years and 4.2 years, respectively, with the first 103 days of the inward transfer method also being devoted to the travel time from the Earth to the deployment point at 0.6 AU, as well. The reason the heliopause is reached in a faster time with the inward transfer method is due to the solar sail achieving maximum speed at 300 days, as opposed to achieving maximum speed with the outward transfer method at approximately two years.
Current travel times to Mars range between 7 and 9 months, which only happens during specified launch windows every two years while relying on the positions of both planets to be aligned at both launch and arrival of any spacecraft going to, or coming from, Mars. Estimating current travel times to the heliopause can be done using NASA's Voyager 1 and Voyager 2 probes, which reached the heliopause at approximately 35 years and 41 years, respectively.
The researchers note that one major question of using solar sails is deceleration, or slowing down, upon arriving at the destination, specifically Mars, and while they mention aerocapture as one solution, they admit this still requires further study.
"Aerocapture maneuvers for hyperbolic trajectories (like flying from Earth to Mars) use the atmosphere to gradually reduce velocity due to drag," Dr. Martin Tajmar, who is a physicist and Professor of Space System at the Dresden University of Technology and a co-author on the study, tells Universe Today.
"Therefore, less fuel is required to enter the Martian orbit. We use this braking maneuver to eliminate the need for additional braking thrusters, which in turn reduces the mass of the spacecraft. We're currently researching what alternative strategies might work for us. Yet the braking method is only one of many different challenges we are currently facing."
While solar sail technology has been proposed by NASA as far back as the 1970s, a recent example of solar sail technology is the NASA Solar Cruiser, which is currently scheduled to launch in February 2025.
More information: Julius Karlapp et al, Ultrafast transfer of low-mass payloads to Mars and beyond using aerographite solar sails, arXiv (2023). DOI: 10.48550/arxiv.2308.16698
Humans are arguably the most adaptable species on Earth. The species' enormous capacity to adapt and live in different environments is thanks to cumulative culture, the transmission and continuous improvement of knowledge and technologies between individuals and generations.
Now, researchers from the School of Arts & Sciences have uncovered a source of inherent tension between individuals and the groups they live in. In a study published in Evolutionary Human Sciences, they show that individuals may be better off with fewer social connections, but groups do best when they consist of very dense social networks.
"Our capacity to accumulate cultural knowledge is part of what makes us human, and it's what has enabled us to settle and live all over the globe," says theoretical biologist Erol Akçay, an associate professor of biology. "In the real world, groups and individuals can benefit from either accumulating more traits or higher proficiency or both."
Akçay and evolutionary biologist Marco Smolla used a model to investigate the coevolution of social networks and cumulative culture. Specifically, they explored the relative benefits of specialist versus generalist cultures for individuals and groups.
Importantly, their model relied on the assumption that in order to learn socially an individual must be exposed to new skills or information multiple times.
"We were interested in complicated traits that a person would need to be exposed to multiple times in order to learn, for example, foraging tactics or making tools," says Smolla, who is a former postdoctoral fellow in Penn's Department of Biology and now a researcher at the Max Planck Institute for Evolutionary Anthropology.
The researchers found that groups benefit most when they have a specialist culture where everyone is highly connected. "Social learning is more effective, and more culture accumulates in these specialist cultures where everyone becomes very proficient at the same handful of traits because there are no wasted learning opportunities," Akçay says. "But there's a conflict between individual-level incentives and what's best for the group."
The model showed that once groups are densely connected, there is an individual incentive to make fewer connections because it allows individuals to focus more and learn more effectively. The researchers also found that while individuals benefit from being innovative, too much innovation is disadvantageous for the group. This mismatch between individual and group interests eventually leads to the disintegration of specialist cultures which results in populations cycling between generalist and specialist cultures.
"Cumulative culture becomes a public good because to maintain it groups have to have this connected network structure, but maintaining that network is individually costly," Akçay says. "I do wonder if these cycling dynamics connect in some way to the archaeological phenomenon where you have a very vibrant culture that builds up and then suddenly collapses."
The researchers also explored how environmental stability might impact social learning and culture. They found that environmental stability promotes more specialized cultures, whereas highly variable environments favor generalist cultures. "Rapid environmental turnover favors disconnected groups because individuals are selected to increase their repertoire size in order to maximize the probability of learning at least some high-payoff traits," Smolla says.
The conflict between individuals and groups could also explain the cross-cultural ubiquity of social rituals that function to maintain social networks and the presence of social norms that enforce social learning at the expense of individual innovation.
"Our results provide a novel hypothesis for the evolution of rituals and social norms that promote social connections," Smolla says. "Such rituals can enforce connectivity and cultural convergence, which might give the group an advantage over competing groups."
More information: Marco Smolla et al, Pathways to cultural adaptation: the coevolution of cumulative culture and social networks, Evolutionary Human Sciences (2023). DOI: 10.1017/ehs.2023.21
