Human social networks are far larger than those of nonhuman primates. Maintaining cohesion in large networks requires a robust mechanism that can accommodate the dense webs of connections within communities. A parsimonious account of how humans achieve social cohesion is mental abstraction, which enables individuals to construct fuzzy network representations that facilitate information flow tracking and mitigate conflict.

Drawing on our previous work on human trust networks, we provide further evidence of how group structure can foster group cohesion. But this work also raises doubts about two central tenets of the target paper: (1) the role assigned to cognitive abilities in group cohesion and stabilization; and (2) the emphasis on group size as the critical variable.

Cyantraniliprole is a widely used insecticide that disrupts calcium homeostasis by binding to ryanodine receptors (RyRs) in the sarcoplasmic reticulum. Insects have a type of RyR with a 47% sequence homology to mammalian RyRs. Due to the high homology and strong affinity of cyantraniliprole for insect RyRs, concerns have been raised about potential adverse effects in mammals. This study aimed to evaluate the effects of cyantraniliprole on the liver and kidneys of male Wistar rat offspring exposed to a dose of 10 mg/kg during gestation and lactation. Thirty-three 80-day-old pregnant Wistar rats were randomly assigned to either a control group or a cyantraniliprole group (10 mg/kg). The treatment period lasted from the 5th gestational day to the 21st lactational day. The offspring were euthanized on postnatal day 55 (puberty) or 90 (adulthood). Blood samples were collected for biochemical assays, and liver and kidney samples were collected for histopathological analysis, oxidative stress biomarkers, and inflammatory profile assessment. The results indicated that exposure to cyantraniliprole caused vacuolation and vascular congestion in the pubertal and adult offspring, as well as significant morphological changes in the liver and kidneys. There was an increase in catalase and glutathione S-transferase activity in response to oxidative stress induced by the insecticide in the liver, with elevated levels of thiobarbituric acid reactive substances in the liver of adult animals and increased myeloperoxidase activity in pubertal animals. These findings suggest that exposure to cyantraniliprole induces significant damage to the organs involved in metabolism and excretion.

Saturated fatty acids, particularly palmitic acid (PA), promote inflammation and contribute to chronic diseases such as type 2 diabetes and cardiovascular disease. PA induces interleukin-1 beta (IL-1β) production in lipopolysaccharide (LPS)-primed macrophages via NLRP3 inflammasome activation; but the underlying mechanism remains unclear. This study investigates whether PA-induced IL-1β production involves cytosolic potassium (K+) depletion. In LPS-primed macrophages, treatment with PA conjugated to bovine serum albumin (PA-BSA) significantly reduced cytosolic K+ levels and increased IL-1β production 2.4-fold. Stearic acid-BSA produced similar effects, whereas BSA-bound oleic, linoleic and docosahexaenoic acids had minimal impact. Voltage-gated potassium (Kv) channel blockers, 4-aminopyridine and tetraethylammonium chloride, attenuated PA-BSA-induced K+ efflux and IL-1β production in LPS-primed macrophages, implicating Kv channels as key mediators. These findings reveal a novel inflammatory pathway in which PA-BSA promotes IL-1β production via Kv channel-dependent K+ efflux, highlighting a mechanistic link between saturated fatty acid exposure and inflammatory signalling.

Dunbar suggests structural, behavioral, and cognitive mechanisms to mitigate the costs of living in large groups. While we generally concur with the notion of group size effects on female productivity, we call for a more explicit treatment of how functional support alleviates social costs and disagree with the outright dismissal of ecological drivers and phylogenetic inertia.

Dunbar exclusively sees groups as arising through the aggregate relationships between individuals and thereby makes the serious omission of not considering the capacity of those individuals to categorize one another as ingroup versus outgroup members.

The paper of Dunbar (2025) on social stress is a strong demonstration that stress in itself can have a purely cognitive origin. The paper shows that the cognitive system can have profound impacts on the hypothalamus. As detailed in my commentary, this opens up new avenues of how to interpret psychiatric conditions, placebo, and other associations between perceptions and vegetative functions in the brain.

Grooming is one strong mechanism allowing primate groups to grow larger and more cohesive, but a reduction in reactive aggression responses can be expected to have contributed to this trend too. There is indeed a partial overlap between the neurobiology of grooming and the neurobiology of reactive aggression.

Challenges of group-living include foundational problems of cooperation and coordination that extend beyond anthropoid primates and may potentially be managed through evolved group-mindedness rather than expanded neocortical size and enhanced capacities for executive functions.

We propose that the emergence of relationship-based social expectations and their evolution into fairness expectations played a key role in the size and cohesion of hominin societies. One of the central challenges of group living is the need to create and sustain stable and mutually beneficial patterns of cooperation. By regulating collaborative interactions, social expectations make group living less stressful.

In this commentary, I suggest a complementary view to the target paper’s idea that primate social metacognition evolved as an adaptation to living in large groups. I present metacognition as a necessary step in the development of complex allostatic systems and suggest that intrinsic and social metacognition are dissociable, which can be studied in the mammalian default mode network.

The Social Brain Hypothesis (SBH) connects primate brain size to social complexity but faces empirical limitations. We propose expanding the SBH by incorporating hippocampal functions across species, demonstrating how cognition emerges from both social and ecological pressures. This extended framework moves beyond cortical-centric models, providing a comprehensive understanding of brain evolution and the origins of human cognitive abilities, including language.

Life history strategies adaptively calibrated to levels of environmental harshness and unpredictability shape not only the fundamental issue of fertility but also whether and to what extent people engage in the structural, behavioral, and cognitive solutions proposed by Dunbar. Considering behavioral ecology can, therefore, add nuance to Dunbar’s novel and important theory.

Grooming and cognition support primate group cohesion but are insufficient for maintaining stability in large groups. We propose tolerance, the capacity to accommodate social stress, as an additional mechanism. Tolerance fosters flexible social skills and cooperation beyond small cliques. Shaped by hormonal adaptation and development, tolerance plays a foundational role in overcoming group size limits by sustaining complex social networks.

Dunbar suggests that social stressors set “glass ceilings” on the evolution of mammalian group size and cohesion. We argue that this glass ceiling narrative conceals three contentious anthropocentric assumptions. First, large stable groups would always be beneficial. Second, grooming is an indicator for maintaining group cohesion. Third, group size is primarily limited by cognitive or behavioral incapacity. We challenge all three assumptions.

Igbo-Ora, a town in southwestern Nigeria, is renowned for exceptionally high dizygotic twin birth rates, recording approximately 45 per 1000 live births. This article explores the factors behind this unique phenomenon by critiquing the community’s perceptions and narrative of the factors responsible for the high twinning rate and comparing these perceptions with biomedical hypotheses. Drawing on 6 months of ethnographic fieldwork — participant observation, 81 semistructured interviews, and FGDs — this study documents local narratives that highlight hereditary ‘twin threads’ —; specific foods, notably Ilasa (okra-leaf soup) and cassava meals; environmental qualities of ‘air’ and ‘water’; and divine sanction as factors responsible for the incidence of twin birth in Igbo-Ora. These local narratives are analyzed against certain biomedical perspectives on maternal age and parity effects, putative genetic variants influencing gonadotrophins, and dietary phytoestrogens. The study found that the community resist single-cause explanations for the incidence of twin birth and instead articulates a complementarity of genetic, ecological, dietary, and spiritual factors. This holistic framing contrasts with and complements prevailing genetic and nutritional theories surrounding the incidence of twin birth. The article argues that future genetic and epidemiological investigations in high-twinning populations must be culturally attuned to ensure accurate phenotype definition, ethical engagement, and translational relevance.