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The anthropoid primates are known for their intense sociality and large brain size. The idea that these might be causally related has given rise to a large body of work testing the ‘social brain hypothesis'. Here, the emphasis has been placed on the political demands of social life, and the cognitive skills that would enable animals to track the machinations of other minds in metarepresentational ways. It seems to us that this position risks losing touch with the fact that brains primarily evolved to enable the control of action, which in turn leads us to downplay or neglect the importance of the physical body in a material world full of bodies and other objects. As an alternative, we offer a view of primate brain and social evolution that is grounded in the body and action, rather than minds and metarepresentation. This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’.

It is widely believed that juvenile male mammals typically engage in higher rates of rough and tumble play (RTP) than do females, in preparation for adult roles involving intense physical competition between males. The consistency of this sex difference across diverse mammalian species has, however, not yet been systematically investigated, limiting our current understanding of its possible adaptive function. This review uses narrative synthesis to (i) evaluate the ubiquity of male-biased RTP across non-human mammals, (ii) identify patterns of variation within and between taxonomic groups, and (iii) propose possible predictors of variation in these differences, including methodological and socio-ecological factors, for investigation by future studies. We find that most species studied do exhibit higher rates or RTP in males than females, while female-biased RTP is rare. Sex differences are smaller and less consistent than expected, with many studies finding similar rates of RTP in males and females. We identify multiple potential socio-ecological predictors of variation in sex differences in RTP, such as intrasexual competition and dietary niche. However, variation is not strongly phylogenetically patterned, suggesting that methodological and environmental factors, such as sample size and play partner availability, are important to consider in future comparative analyses.Significance statementRough and tumble play (RTP) is thought to be vital for developing physical skills necessary for aggressive competition in adulthood, explaining an apparently widespread sex difference in RTP in mammals whereby immature males are more likely to engage in this behaviour than females. However, no prior study has systematically investigated the extent to which a male bias in RTP is consistent across diverse mammalian species. We find that although RTP is commonly male biased, findings were highly variable both within- and between-species, and equal participation in RTP by males and females is more common than widely assumed. Our review suggests several potential predictors of variation in sex differences in RTP, particularly levels of intrasexual competition in both males and females. However, our findings also suggest the importance of considering methodological in addition to socio-ecological factors for future research.

Perceptions of physical attractiveness vary across cultural groups, particularly for female body size and shape. It has been hypothesized that visual media propagates Western "thin ideals." However, because cross-cultural studies typically consider groups highly differentiated on a number of factors, identifying the causal factors has thus far been impossible. In the present research, we conducted "naturalistic" and controlled experiments to test the influence of media access on female body ideals in a remote region of Nicaragua by sampling from villages with and without regular TV access. We found that greater TV consumption remained a significant predictor of preferences for slimmer, curvier female figures after controlling for a range of other factors in an ethnically balanced sample of 299 individuals (150 female, aged 15-79) across 7 villages. Within-individual analyses in 1 village over 3 years also showed an association between increased TV consumption and preferences for slimmer figures among some participants. Finally, an experimental study in 2 low-media locations demonstrates that exposure to media images of fashion models can directly impact participants' body size ideals. We provide the first converging cross-sectional, longitudinal, and experimental evidence from field-based research, that media exposure can drive changes in perceptions of female attractiveness. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

To examine the effectiveness of antithrombotic medications to prevent venous stent malfunction for iliocaval occlusive disease. A retrospective analysis was performed on 62 patients who underwent technically successful endovascular iliocaval stent placement between May 2008 and April 2017. Clinical records were reviewed for demographic information, procedure details, post-stenting antithrombotic prophylaxis and stent patency on follow-up. Stent malfunction was defined as > 50% stenosis or occlusion at follow-up. Risk factors for stent malfunction were assessed with univariable and multiple Cox proportional hazard models. The median follow-up period was 11.6 months (range 0.1–76.4). Overall primary and secondary cumulative patency rates at 12 months were 70.0% and 92.4%, respectively. After stent placement, 97% of patients received anticoagulation with warfarin, enoxaparin or a factor Xa inhibitor. In addition, 61% received antiplatelet prophylaxis with aspirin, clopidogrel or a combination. In multiple Cox regression analysis, post-stenting antiplatelet use remained significantly associated with primary stent patency (HR = 0.28, P = 0.022). After iliocaval venous stenting, stent patency was best predicted by concomitant antiplatelet and anticoagulation therapy rather than anticoagulation alone. This novel finding warrants further research underlying mechanisms leading to venous stent thrombosis, and has implications for optimal medical management after venous stenting.

There is ongoing debate about how and why the menstrual cycle affects women’s attraction to men. According to the dual sexuality hypothesis, women form pair-bond relationships with men who provide care but also obtain genetic benefits by biasing mating effort towards men with high-fitness genes during the fertile phase. By contrast, the commitment hypothesis proposes that attachment bonds with primary partners function to strengthen pair-bond relationships by enhancing in-pair attraction at the fertile phase, rather than extrapair attraction. We tested these hypotheses by measuring women’s daily sexual and emotional attraction towards men over the whole menstrual cycle. We employed 1) a urinary luteinizing hormone test to determine the day of ovulation, 2) a 5-part classification of menstrual cycle that identifies a distinct peri-ovulatory phase, and 3) individualized phase identification for each participant. There was a mid-cycle rise in extrapair sexual desire. Women gave and received more care from partners during the menstrual than the mid-cycle phases. Partner’s sexual attractiveness and mutual commitment did not moderate these findings. The results do not support either the dual sexuality or commitment hypotheses, and imply that female self-reported sexual desire is not strictly dependent on cyclic hormonal changes. Our results are more consistent with a recently proposed `spandrel’ hypothesis, positing cycle phase effects as a nonfunctional by-product of raised estradiol. Additionally, we found that, with the date of ovulation estimated by luteinizing hormone tests, 45% of ovulations were misclassified by the backward counting method, which urges caution in interpreting results based on counting methods.

in addressing the question of whether human prefrontal cortex (PFC) is “disproportionately larger in humans compared with nonhuman primates” in their article in PNAS, Donahue et al. (1) gloss over the distinction between proportional and relative size. Agreeing with previous work (2⇓–4), they show that PFC occupies a larger proportion of the cerebral cortex in humans than in chimpanzees and a larger proportion in chimpanzees than in macaques. Contrary to their presentation of the debate, this fact is uncontroversial. However, proportional size is often a misleading functional metric because of nonlinear, or allometric, scaling: A biological structure can differ across species as a proportion of overall size and yet be functionally equivalent (5) (Fig. 1). PFC volume proportion is predictable from overall brain size, even among nonhuman species (2⇓–4). This increase in volume proportions may be a scaling effect, with no consequences for functional influence exerted by PFC if there are different scaling constraints on different cortical regions (6). For example, disproportionate PFC white matter volume and cell size increases may be necessary to maintain long-range neural connectivity and neural transmission speed in larger brains and bodies (4, 6, 7). Indeed, this is consistent with Donahue et al.’s observation that white matter largely explains the species differences they observe in PFC proportional volume.

While the human brain is clearly large relative to body size, less is known about the timing of brain and brain component expansion within primates and the relative magnitude of volumetric increases. Using Bayesian phylogenetic comparative methods and data for both extant and fossil species, we identified that a distinct shift in brain-body scaling occurred as hominins diverged from other primates, and again as humans and Neanderthals diverged from other hominins. Within hominins, we detected a pattern of directional and accelerating evolution towards larger brains, consistent with a positive feedback process in the evolution of the human brain. Contrary to widespread assumptions, we found that the human neocortex is not exceptionally large relative to other brain structures. Instead, our analyses revealed a single increase in relative neocortex volume at the origin of haplorrhines, and an increase in relative cerebellar volume in apes., eLife digest Humans have much larger brains than other primates, but it is not clear exactly when and how this difference emerged during evolution. Some scientists believe that the expansion of a part of the brain called the neocortex – which handles sight, hearing, conscious decision-making and language – drove the increase in the size of the human brain. Newer studies have challenged that idea. One way to learn more about how humans evolved bigger brains is to compare the size of the brain, and specific parts of the brain, between humans and our closest relatives: non-human primates. To make accurate comparisons, scientists must account for many factors. Closely related primates may have more similar traits because they more recently shared a common ancestor. This means the evolutionary relationships between species need to be considered. Larger animals also tend to have larger brains so it is important to consider body size, too. Now, Miller at al. show that the human brain is much larger than expected even after accounting for these factors, and that increases in brain size accelerated over the course of early human evolution. In the analyses, the brain and skull sizes of different living primate species, like chimpanzees and gorillas, and fossils of extinct primates, including Neanderthals, were compared using mathematical models. These findings suggest that larger brains provided fitness advantages that led to large brain sizes in modern humans and Neanderthals. These increases in brain size were not driven by disproportionate growth in the neocortex alone, but rather by increases in the size of many parts of the brain. Increases in the relative size of the cerebellum, which is essential for balance and movement, were also important.

Identifying sets of items that are equivalent to one another is a problem common to many fields. Systems addressing this generally have at their core a function s(d_i, d_j) for computing the similarity between pairs of records d_i, d_j. The output of s() can be interpreted as a weighted graph where edges indicate the likelihood of two records matching. Partitioning this graph into equivalence classes is non-trivial due to the presence of inconsistencies and imperfections in s(). Numerous algorithmic approaches to the problem have been proposed, but (1) it is unclear which approach should be used on a given dataset; (2) the algorithms do not generally output a confidence in their decisions; and (3) require error-prone tuning to a particular notion of ground truth. We present SuperPart, a scalable, supervised learning approach to graph partitioning. We demonstrate that SuperPart yields competitive results on the problem of detecting equivalent records without manual selection of algorithms or an exhaustive search over hyperparameters. Also, we show the quality of SuperPart's confidence measures by reporting Area Under the Precision-Recall Curve metrics that exceed a baseline measure by 11%. Finally, to bolster additional research in this domain, we release three new datasets derived from real-world Amazon product data along with ground-truth partitionings.

Tensioned graphene membranes are of interest both for fundamental physics and for applications ranging from water filtration to nanomechanical resonators. It is generally assumed that these membranes have a stretching modulus of about 340 N/m and a negative, temperature-independent thermal expansion coefficient due to transverse phonon modes. In this paper, we study the two-dimensional Young's modulus and thermal expansion of graphene as functions of temperature by using laser interferometry to detect the static displacement of the membrane in a cryostat. Surprisingly, we find that the modulus decreases strongly with increasing temperature, which leads to a positive temperature-dependent thermal expansion coefficient. We show that the thermally rippled membrane theory is not consistent with our data, while the effects of surface contaminants typically present on these membranes may explain the observed behavior. Our experiments undermine long-standing assumptions about tensioned two-dimensional membranes, but are consistent with puzzling behavior observed in previous experiments on graphene resonators.

OBJECTIVE. Transjugular intrahepatic portosystemic shunt (TIPS) creation increases the risk of hepatic encephalopathy due to overshunting. Techniques exist to secondarily reduce the shunt for refractory encephalopathy. The purpose of this article is to describe a technique for primary TIPS restriction using a balloon-expandable stent within the transvenous hepatic track followed by deployment of a self-expanding polytetrafluoroethylene–lined stent-graft within the balloon-expandable stent to create the TIPS. CONCLUSION. This technique enables control over the degree of portosystemic shunting in elective TIPS creation.

Graphene is a promising flexible, highly transparent, and elementally abundant electrode for organic electronics. Typical methods utilized to transfer large-area films of graphene synthesized by chemical vapor deposition on metal catalysts are not compatible with organic thin-films, limiting the integration of graphene into organic optoelectronic devices. This article describes a graphene transfer process onto chemically sensitive organic semiconductor thin-films. The process incorporates an elastomeric stamp with a fluorinated polymer release layer that can be removed, post-transfer, via a fluorinated solvent; neither fluorinated material adversely affects the organic semiconductor materials. We used Raman spectroscopy, atomic force microscopy, and scanning electron microscopy to show that chemical vapor deposition graphene can be successfully transferred without inducing defects in the graphene film. To demonstrate our transfer method's compatibility with organic semiconductors, we fabricate three classes of organic thin-film devices: graphene field effect transistors without additional cleaning processes, transparent organic light-emitting diodes, and transparent small-molecule organic photovoltaic devices. These experiments demonstrate the potential of hybrid graphene/organic devices in which graphene is deposited directly onto underlying organic thin-film structures.

Burkart et al. conflate the domain-specificity of cognitive processes with the statistical pattern of variance in behavioural measures that partly reflect those processes. General intelligence is a statistical abstraction, not a cognitive trait, and we argue that the former does not warrant inferences about the nature or evolution of the latter.

Comparative studies have identified a wide range of behavioural and ecological correlates of relative brain size, with results differing between taxonomic groups, and even within them. In primates for example, recent studies contradict one another over whether social or ecological factors are critical. A basic assumption of such studies is that with sufficiently large samples and appropriate analysis, robust correlations indicative of selection pressures on cognition will emerge. We carried out a comprehensive re-examination of correlates of primate brain size using two large comparative datasets and phylogenetic comparative methods. We found evidence in both datasets for associations between brain size and ecological variables (home range size, diet and activity period), but little evidence for an effect of social group size, a correlation which has previously formed the empirical basis of the Social Brain Hypothesis. However, reflecting divergent results in the literature, our results exhibited instability across datasets, even when they were matched for species composition and predictor variables. We identify several potential empirical and theoretical difficulties underlying this instability and suggest that these issues raise doubts about inferring cognitive selection pressures from behavioural correlates of brain size.

Atomically thin materials such as graphene and transition metal dichalcogenides are being developed for a range of optoelectronic devices, but their applications are currently limited by low light absorption. Here, we describe a dielectric cavity design with chirped Bragg reflectors for broadband coherent absorption. The chirped cavity absorption is calculated by the transfer matrix method and optimized using the Nelder–Mead optimization protocol. We numerically demonstrate that with cavity enhancement, a monolayer MoS2 photodetector absorbs as much as 33% of incident visible light over a 300 nm bandwidth, and the external quantum efficiency of an atomically thin monolayer graphene/monolayer MoS2 solar cell can be enhanced 3.6 times to a predicted value of 7.09%. The proposed layered dielectric structures operate across a wide range of incident angles and could enable applications for atomically thin photodetectors or solar cells.

Life history is a robust correlate of relative brain size: large-brained mammals and birds have slower life histories and longer lifespans than smaller-brained species. One influential adaptive hypothesis to account for this finding is the Cognitive Buffer Hypothesis (CBH). The CBH proposes that large brains permit greater behavioural flexibility and thereby buffer the animal from unpredictable environmental challenges, allowing reduced mortality and increased lifespan. In contrast, the Developmental Costs Hypothesis (DCH) suggests that life-history correlates of brain size reflect the extension of maturational processes needed to accommodate the evolution of large brains. The hypotheses are not mutually exclusive but do make different predictions. Here we test novel predictions of the hypotheses in primates: examining how the volume of brain components with different developmental trajectories correlate with relevant phases of maternal investment, juvenile period and post-maturational lifespan. Consistent with the DCH, structures with different allocations of growth to pre-natal versus post-natal development exhibit predictably divergent correlations with the associated periods of maternal investment and pre-maturational lifespan. Contrary to the CBH, adult lifespan is uncorrelated with either whole brain size or the size of individual brain components once duration of maternal investment is accounted for. Our results substantiate and elaborate on the role of maternal investment and offspring development in brain evolution, suggest that brain components can evolve partly independently through modifications of distinct developmental mechanisms, and imply that postnatal maturational processes involving interaction with the environment may be particularly crucial for the development of cerebellar function. They also provide an explanation for why apes have relatively extended maturation times, which relate to the relative expansion of the cerebellum in this clade.

One of the most pervasive assumptions about human brain evolution is that it involved relative enlargement of the frontal lobes. We show that this assumption is without foundation. Analysis of five independent data sets using correctly scaled measures and phylogenetic methods reveals that the size of human frontal lobes, and of specific frontal regions, is as expected relative to the size of other brain structures. Recent claims for relative enlargement of human frontal white matter volume, and for relative enlargement shared by all great apes, seem to be mistaken. Furthermore, using a recently developed method for detecting shifts in evolutionary rates, we find that the rate of change in relative frontal cortex volume along the phylogenetic branch leading to humans was unremarkable and that other branches showed significantly faster rates of change. Although absolute and proportional frontal region size increased rapidly in humans, this change was tightly correlated with corresponding size increases in other areas and whole brain size, and with decreases in frontal neuron densities. The search for the neural basis of human cognitive uniqueness should therefore focus less on the frontal lobes in isolation and more on distributed neural networks.

Internalization of a thin ideal has been posited as a key risk factor in the development of pathological eating attitudes. Cross-culturally, studies have found a preference for heavier bodies in populations with reduced access to visual media compared to Western populations. As yet, however, there has been little attempt to control for confounding variables in order to isolate the effects of media exposure from other cultural and ecological factors. Here, we examined preferences for female body size in relation to television consumption in Nicaraguan men and women, while controlling for the potential confounding effects of other aspects of Westernization and hunger. We included an urban sample, a sample from a village with established television access, and a sample from a nearby village with very limited television access. The highest BMI preferences were found in the village with least media access, while the lowest BMI preferences were found in the urban sample. Data from the rural sample with established television access were intermediate between the two. Amongst rural women in particular, greater television consumption was a stronger predictor of body weight preferences than acculturation, education, hunger, or income. We also found some evidence for television consumption increasing the likelihood of women seeking to lose weight, possibly via body shape preferences. Overall, these results strongly implicate television access in establishing risk factors for body image disturbances in populations newly gaining access to Western media.

Recent decades have seen rapid development of new analytical methods to investigate patterns of interspecific variation. Yet these cutting-edge statistical analyses often rely on data of questionable origin, varying accuracy, and weak comparability, which seem to have reduced the reproducibility of studies. It is time to improve the transparency of comparative data while also making these improved data more widely available. We, the authors, met to discuss how transparency, usability, and reproducibility of comparative data can best be achieved. We propose four guiding principles: 1) data identification with explicit operational definitions and complete descriptions of methods; 2) inclusion of metadata that capture key characteristics of the data, such as sample size, geographic coordinates, and nutrient availability (for example, captive versus wild animals); 3) documentation of the original reference for each datum; and 4) facilitation of effective interactions with the data via user friendly and transparent interfaces. We urge reviewers, editors, publishers, database developers and users, funding agencies, researchers publishing their primary data, and those performing comparative analyses to embrace these standards to increase the transparency, usability, and reproducibility of comparative studies.

Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of mosaic change at the level of the functional systems and more complex genetic and developmental mechanisms. These hypotheses are not mutually exclusive but make different predictions. We review recent genetic and neurodevelopmental evidence, concluding that functional rather than developmental constraints are the main cause of the observed patterns.

Commentary on Herculano-Houzel S (2015): Decreasing Sleep Requirement with Increasing Numbers of Neurons as a Driver for Bigger Brains and Bodies in Mammalian Evolution. Proc Biol Sci 282:20151853

Laland and colleagues have sought to challenge the proximate–ultimate distinction claiming that it imposes a unidirectional model of causation, is limited in its capacity to account for complex biological phenomena, and hinders progress in biology. In this article the core of their argument is critically analyzed. It is claimed that contrary to their claims Laland et al. rely upon the proximate–ultimate distinction to make their points and that their alternative conception of reciprocal causation refers to phenomena that were already accounted for by standard theory.

Purpose To describe the use of intravascular ultrasound (US) guidance for creation of transjugular intrahepatic portosystemic shunts (TIPSs) in humans. Materials and Methods The initial 25 cases of intravascular US–guided TIPS were retrospectively compared versus the last 75 conventional TIPS cases during the same time period at the same institution in terms of the number of needle passes required to establish portal vein (PV) access, fluoroscopy time, and needle pass–related complications. Results Intravascular US–guided TIPS creation was successful in all cases, and there was no statistically significant difference in number of needle passes, fluoroscopy time, or needle pass–related complications between TIPS techniques. Intravascular US–guided TIPS creation was successful in cases in which conventional TIPS creation had failed as a result of PV thrombosis or distorted anatomy. Intravascular US guidance for TIPS creation was additionally useful in a patient with Budd–Chiari syndrome and in a patient with intrahepatic tumors. Conclusions Intravascular US is a safe and reproducible means of real-time image guidance for TIPS creation, equivalent in efficacy to conventional fluoroscopic guidance. Real-time sonographic guidance with intravascular US may prove advantageous for cases in which there is PV thrombus, distorted anatomy, Budd–Chiari syndrome, or hepatic tumors.

Much attention has focused on the dramatic expansion of the forebrain, particularly the neocortex, as the neural substrate of cognitive evolution. However, though relatively small, the cerebellum contains about four times more neurons than the neocortex. I show that commonly used comparative measures such as neocortex ratio underestimate the contribution of the cerebellum to brain evolution. Once differences in the scaling of connectivity in neocortex and cerebellum are accounted for, a marked and general pattern of correlated evolution of the two structures is apparent. One deviation from this general pattern is a relative expansion of the cerebellum in apes and other extractive foragers. The confluence of these comparative patterns, studies of ape foraging skills and social learning, and recent evidence on the cognitive neuroscience of the cerebellum, suggest an important role for the cerebellum in the evolution of the capacity for planning, execution and understanding of complex behavioural sequences—including tool use and language. There is no clear separation between sensory–motor and cognitive specializations underpinning such skills, undermining the notion of executive control as a distinct process. Instead, I argue that cognitive evolution is most effectively understood as the elaboration of specialized systems for embodied adaptive control.

We demonstrate terahertz (THz) imaging and spectroscopy of single-layer graphene deposited on an intrinsic Si substrate using THz time-domain spectroscopy. A single-cycle THz pulse undergoes multiple internal reflections within the Si substrate, and the THz absorption by the graphene layer accumulates through the multiple interactions with the graphene/Si interface. We exploit the large absorption of the multiply reflected THz pulses to acquire high-contrast THz images of graphene. We obtain local sheet conductivity of the graphene layer analyzing the transmission data with thin-film Fresnel formula based on the Drude model.