pnas.org

Natural ecosystems are increasingly threatened by global agricultural supply chains, and a narrow policy focus on forests has fueled agricultural expansion into ecologically significant but severely overlooked non-forest ecosystems, including grasslands and open wetlands. While a few emerging policies attempt to protect non-forest ecosystems, a globally consistent assessment of their conversion extent and drivers, especially related to livestock production and commodity-specific supply chain demand, remains lacking. Here, we conducted a spatially explicit analysis to identify pasture and cropland expansion into non-forest ecosystems between 2005 and 2020, as well as conversion-linked primary agricultural commodities and their underlying demand drivers (end uses and final market destinations). We found that the conversion rate of natural non-forest ecosystems was nearly four times that of lands with tree cover exceeding 5 m (a common forest height threshold), with Brazil contributing 13% of the global total and Russia, India, China, and the United States each contributing about 6%. While drivers varied greatly across regions, globally 50% of the conversion was linked to pasture, and 27, 17, and 6% to cropland for food, feed, and other uses (mainly bioenergy), respectively. Among conversion-linked commodities, most livestock-associated products served domestic demand, while 32% of feed crops and 20% of all crops were exported, with export shares reaching 70 to 80% in Brazil and Argentina. These findings reveal important areas for non-forest ecosystem conservation and highlight the need for integrated policies to prevent leakage across different ecosystems and different sustainable development goals while also aligning local actions with global supply chain governance.

A groundbreaking 2026 study reveals that early humans in Europe used a sophisticated system of geometric signs 40,000 years ago, with complexity matching early writing systems[^1]. Researchers analyzed over 3,000 signs on 260 Aurignacian artifacts from the Swabian Jura region, dated between 43,000-34,000 years ago[^2].

This study evaluates the largest automated speed enforcement program in the United States—2,000 cameras deployed across New York City from 2014 to 2023. Leveraging data on 700,000 collisions and 18 million speeding tickets, the analysis finds that cameras lead to persistent and sustained reductions in crashes. These results demonstrate that automated enforcement can meaningfully improve road safety while avoiding the harms associated with conventional traffic safety approaches.

Preprint

Seven studies using experimental and naturalistic methods reveal that upper-class individuals behave more unethically than lower-class individuals. In studies 1 and 2, upper-class individuals were more likely to break the law while driving, relative to lower-class individuals. In follow-up laboratory studies, upper-class individuals were more likely to exhibit unethical decision-making tendencies (study 3), take valued goods from others (study 4), lie in a negotiation (study 5), cheat to increase their chances of winning a prize (study 6), and endorse unethical behavior at work (study 7) than were lower-class individuals. Mediator and moderator data demonstrated that upper-class individuals’ unethical tendencies are accounted for, in part, by their more favorable attitudes toward greed.

Seven studies using experimental and naturalistic methods reveal that upper-class individuals behave more unethically than lower-class individuals. In studies 1 and 2, upper-class individuals were more likely to break the law while driving, relative to lower-class individuals. In follow-up laboratory studies, upper-class individuals were more likely to exhibit unethical decision-making tendencies (study 3), take valued goods from others (study 4), lie in a negotiation (study 5), cheat to increase their chances of winning a prize (study 6), and endorse unethical behavior at work (study 7) than were lower-class individuals. Mediator and moderator data demonstrated that upper-class individuals’ unethical tendencies are accounted for, in part, by their more favorable attitudes toward greed.

Here, we present archaeobotanical data for ancient barley grains in association with sickle blades and grinding stones from the cave of Toda in the foothills of southern Uzbekistan.

These analyses revealed that the East Asian specimens of Harbin and Dali show an exceptionally high concordance with the Denisovan profile, surpassing all other examined Middle Pleistocene hominin specimens, including Neanderthals. Specifically, 15 out of 18 of Dali’s features and 16 out of 18 of Harbin’s matched Denisovan predictions. These findings are robust to overall skull size and to correlations between phenotypes. We also found that Kabwe 1 shows a strong affinity to the Denisovan–Neanderthal clade and might be placed near its root. Our results show that gene regulatory phenotyping may assist in classifying poorly understood specimens.

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Here, we present archaeobotanical data for ancient barley grains in association with sickle blades and grinding stones from the cave of Toda in the foothills of southern Uzbekistan. This finding helps shed light on one of the greatest mysteries in central Asian archaeology—how did the Kelteminar people live? We complement our data with a suite of radiocarbon dates, a detailed palynological study, an analysis of wood charcoal remains, and a detailed analysis of all aspects of the archaeological remains. These data, collectively, paint the clearest picture thus far of the prehistory of this poorly studied corner of the ancient world.

Small anatomical details can significantly influence how marine animals organize themselves, yet such interactions are rarely visible in fossils. We report exceptionally preserved soft, bristle-like structures ("setae") on 436-My-old brachiopods, enabling analysis of ancient behavior. Using advanced imaging and statistical analysis, we identified a regular, checkerboard-like spacing pattern among these organisms, closely corresponding to their setae length. This demonstrates that these delicate structures played an important role in maintaining spacing between individuals, thereby influencing population organization on the ancient seabed. Our findings point to a previously unrecognized mechanism shaping ecosystem structure in deep time, demonstrating how subtle anatomical features could exert notable ecological impacts in their ancient environments.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID affect large numbers of people, and constitute a substantial burden to the U.S. and global economies. The article by Eckey et al., in this issue of PNAS (1), adds to the growing evidence that the two illnesses have much in common. Moreover, the illnesses may represent just two examples of an even larger, recently recognized class of illness: post-acute infection syndromes (PAIS) (2).

The underlying factors that lead to specific strains within a species to emerge as human pathogens remain mostly enigmatic. Toxigenic clones of the cholera agent, Vibrio cholerae, are encompassed within one phylogenomic clade, the pandemic cholera group (PCG). Here, we investigate the molecular and evolutionary factors that explain the confined nature of this group. Our analyses determined that the emergence of PCG is largely dependent on the acquisition of unique modular gene clusters and allelic variations that confer a competitive advantage during intestinal colonization. These allelic variations act as a critical bottleneck that elucidate the isolated emergence of PCG and provides a tractable blueprint for the study of the emergence of pathogenic clones within an environmental population.

When could scientists have first known that fossil fuel burning was significantly altering global climate?

ADAM (a disintegrin and metalloproteinase)-17 is a crucial enzyme that activates proteins involved in development, immune defense, and tissue repair. Its dysregulation is linked to diseases such as cancer, autoimmune conditions, and COVID-19. Using advanced cryogenic electron microscopy (cryo-EM) techniques, we resolved the structure of ADAM17 bound to its regulator protein, inactive rhomboid proteins (iRhom)-2, and identified key structural elements essential for its activity and regulation. We uncovered a key regulatory element within the cytoplasmic domain iRhom2 and clarified the role of the ADAM17 prodomain, challenging prior activation models. Additionally, we detailed the inhibitory mechanism of the therapeutic antibody MEDI3622. This work provides a foundation for designing therapies targeting ADAM17-related diseases, offering strategies to address critical human health conditions.

archived (Wayback Machine)

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Analyzing behavioral sequences through three different approaches, we have found remarkable similarities in the dynamics of behavior across three species in the wild.

As AI tools become increasingly prevalent in workplaces, understanding the social dynamics of AI adoption is crucial. Through four experiments with over 4,400 participants, we reveal a social penalty for AI use: Individuals who use AI tools face negative judgments about their competence and motivation from others. These judgments manifest as both anticipated and actual social penalties, creating a paradox where productivity-enhancing AI tools can simultaneously improve performance and damage one’s professional reputation. Our findings identify a potential barrier to AI adoption and highlight how social perceptions may reduce the acceptance of helpful technologies in the workplace.

As AI tools become increasingly prevalent in workplaces, understanding the social dynamics of AI adoption is crucial. Through four experiments with over 4,400 participants, we reveal a social penalty for AI use: Individuals who use AI tools face negative judgments about their competence and motivation from others. These judgments manifest as both anticipated and actual social penalties, creating a paradox where productivity-enhancing AI tools can simultaneously improve performance and damage one’s professional reputation. Our findings identify a potential barrier to AI adoption and highlight how social perceptions may reduce the acceptance of helpful technologies in the workplace.

As AI tools become increasingly prevalent in workplaces, understanding the social dynamics of AI adoption is crucial. Through four experiments with over 4,400 participants, we reveal a social penalty for AI use: Individuals who use AI tools face negative judgments about their competence and motivation from others. These judgments manifest as both anticipated and actual social penalties, creating a paradox where productivity-enhancing AI tools can simultaneously improve performance and damage one’s professional reputation. Our findings identify a potential barrier to AI adoption and highlight how social perceptions may reduce the acceptance of helpful technologies in the workplace.

As AI tools become increasingly prevalent in workplaces, understanding the social dynamics of AI adoption is crucial. Through four experiments with over 4,400 participants, we reveal a social penalty for AI use: Individuals who use AI tools face negative judgments about their competence and motivation from others. These judgments manifest as both anticipated and actual social penalties, creating a paradox where productivity-enhancing AI tools can simultaneously improve performance and damage one’s professional reputation. Our findings identify a potential barrier to AI adoption and highlight how social perceptions may reduce the acceptance of helpful technologies in the workplace.

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Air quality estimates are the primary source of information regarding exposure to pollution, and their quality is important for public health, policy, and society. These estimates rely on the coverage of monitoring infrastructure across the nation.

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Beef is more resource intensive per gram of edible protein than most other food items. Yet, grass-fed beef is sometimes promoted as environmentally desirable based on the expectation that cattle grazing may enhance soil carbon sequestration, thus offsetting production emissions. We quantitatively examine this view by integrating empirical observations with a beef herd model that uses standard animal science equations. We find that even under optimistic rangeland sequestration, grass-fed beef is not less carbon intensive than industrial beef and 3 to 40 times as carbon intensive as most plant and animal alternatives.

Abstract: Experiencing negative content through art has a unique power to transform our perceptions and foster engagement. While this idea has been widely discussed, empirical evidence is scarce, since experimental testing of art experiences poses significant challenges. Here, we aimed to fill this gap by quantifying and comparing individuals’ preference for engaging with art and nonart depicting matched negative content via two behavioral measures: the choice to engage vs. avoid and the duration of engagement.

Abstract: Experiencing negative content through art has a unique power to transform our perceptions and foster engagement. While this idea has been widely discussed, empirical evidence is scarce, since experimental testing of art experiences poses significant challenges. Here, we aimed to fill this gap by quantifying and comparing individuals’ preference for engaging with art and nonart depicting matched negative content via two behavioral measures: the choice to engage vs. avoid and the duration of engagement.

Collective cognition is often mentioned as one of the advantages of group living. But which factors actually facilitate group smarts? To answer this, we compared how individuals and groups of either ants or people tackle an identical geometrical puzzle. We find that when ants work in groups, their performances rise significantly. Groups of people do not show such improvement and, when their communication is restricted, even display deteriorated performances. What is the source of such differences? An ant’s simplicity prevents her from solving the puzzle on her own but facilitates effective cooperation with nest-mates. A single person is cognitively sophisticated and solves the problem efficiently but this leads to interpersonal variation that stands in the way of efficient group performance.

study in Nature Cell Biology finds that they play a previously little known role in gene regulation—a role that may influence some cancer cells’ responsiveness to different treatment types.

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Postdoctoral training is a career stage often described as a demanding and anxiety-laden time when many promising PhDs see their academic dreams slip away due to circumstances beyond their control. We use a unique dataset of academic publishing and careers to chart the more or less successful postdoctoral paths. We build a measure of academic success on the citation patterns two to five years into a faculty career. Then, we monitor how students’ postdoc positions—in terms of relocation, change of topic, and early well-cited papers—relate to their early-career success.

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Pesticides are critical to agricultural intensification but can negatively impact human health. We show that as soy cultivation spread across Brazil, agricultural pesticide exposure was associated with increased childhood cancer mortality among the broader population indirectly exposed to these chemicals. We find that populations were exposed to pesticides through the water supply, but negative health effects were mitigated by access to high-quality cancer treatment centers. Our results support policies to strengthen pesticide regulation, especially in contexts intensifying their food production systems, and increased public health attention to pesticide exposure in the broader community.

Interesting paper, about the alleged ability of LLMs* to judge the grammaticality of sentences - something that humans are rather good at. Eight phenomena were tested, and LLMs performed extremely poorly.

This paper provides some actual data on the bouba-kiki effect, where certain words are non-arbitrarily associated with certain meanings, by analysing the frequency of sounds used in words conveying a specific meaning (as “bone”, “stone”, etc.). It takes cognates and areal effects into account.