Tool use induces complex and flexible plasticity of human body representations

Plasticity of body representation fundamentally underpins human tool use. Recent studies have demonstrated remarkably complex plasticity of body representation in humans, showing that such plasticity: (1) occurs flexibly across multiple time-scales, and (2) involves multiple body representations responding differently to tool use. Such findings reveal remarkable sophistication of body plasticity in humans, suggesting that Vaesen may overestimate the similarity of such mechanisms in humans and non-human primates

Body odor quality predicts behavioral attractiveness in humans

Growing effort is being made to understand how different attractive physical traits co-vary within individuals, partly because this might indicate an underlying index of genetic quality. In humans, attention has focused on potential markers of quality such as facial attractiveness, axillary odor quality, the second-to-fourth digit (2D:4D) ratio and body mass index (BMI). Here we extend this approach to include visually-assessed kinesic cues (nonverbal behavior linked to movement) which are statistically independent of structural physical traits. The utility of such kinesic cues in mate assessment is controversial, particularly during everyday conversational contexts, as they could be unreliable and susceptible to deception. However, we show here that the attractiveness of nonverbal behavior, in 20 male participants, is predicted by perceived quality of their axillary body odor. This finding indicates covariation between two desirable traits in different sensory modalities. Depending on two different rating contexts (either a simple attractiveness rating or a rating for long-term partners by 10 female raters not using hormonal contraception), we also found significant relationships between perceived attractiveness of nonverbal behavior and BMI, and between axillary odor ratings and 2D:4D ratio. Axillary odor pleasantness was the single attribute that consistently predicted attractiveness of nonverbal behavior. Our results demonstrate that nonverbal kinesic cues could reliably reveal mate quality, at least in males, and could corroborate and contribute to mate assessment based on other physical traits

Recent origin of low trabecular bone density in modern humans

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations

Clavicle length and shoulder breadth in hominoid evolution

For a given body mass, hominoids have longer clavicles than typical monkeys, reflecting the laterad reorientation of the hominoid glenoid. Relative length of the clavicle varies among hominoids, with orangutans having longer clavicles than expected for body mass and gorillas and chimpanzees having shorter clavicles than expected. Modern humans conform to the general hominoid distribution, but Neandertals have longer clavicles than expected for their size. [TRUNCATED

Effects of MDMA on body temperature in humans

Hyperthermia is a severe complication associated with the recreational use of 3,4-methylenedioxymethamphetamine(MDMA, Ecstasy). In this review, the clinical laboratory studies that tested the effects of MDMA on body temperature are summarized. The mechanisms that underlie the hyperthermic effects of MDMA in humans and treatment of severe hyperthermia are presented. The data show that MDMA produces an acute and dose-dependent rise in core body temperature in healthy subjects. The increase in body temperature is in the range of 0.2-0.8C and does not result in hyperpyrexia (>40C) in a controlled laboratory setting. However, moderately hyperthermic body temperatures >38.0C occur frequently at higher doses, even in the absence of physical activity and at room temperature. MDMA primarily releases serotonin and norepinephrine. Mechanistic clinical studies indicate that the MDMA-induced elevations in body temperature in humans partially depend on the MDMA-induced release of norepinephrine and involve enhanced metabolic heat generation and cutaneous vasoconstriction, resulting in impaired heat dissipation. The mediating role of serotonin is unclear. The management of sympathomimetic toxicity and associated hyperthermia mainly includes sedation with benzodiazepines and intravenous fluid replacement. Severe hyperthermia should primarily be treated with additional cooling and mechanical ventilation

Social interactions through the eyes of macaques and humans

Group-living primates frequently interact with each other to maintain social bonds as well as to compete for valuable resources. Observing such social interactions between group members provides individuals with essential information (e.g. on the fighting ability or altruistic attitude of group companions) to guide their social tactics and choice of social partners. This process requires individuals to selectively attend to the most informative content within a social scene. It is unclear how non-human primates allocate attention to social interactions in different contexts, and whether they share similar patterns of social attention to humans. Here we compared the gaze behaviour of rhesus macaques and humans when free-viewing the same set of naturalistic images. The images contained positive or negative social interactions between two conspecifics of different phylogenetic distance from the observer; i.e. affiliation or aggression exchanged by two humans, rhesus macaques, Barbary macaques, baboons or lions. Monkeys directed a variable amount of gaze at the two conspecific individuals in the images according to their roles in the interaction (i.e. giver or receiver of affiliation/aggression). Their gaze distribution to non-conspecific individuals was systematically varied according to the viewed species and the nature of interactions, suggesting a contribution of both prior experience and innate bias in guiding social attention. Furthermore, the monkeys’ gaze behavior was qualitatively similar to that of humans, especially when viewing negative interactions. Detailed analysis revealed that both species directed more gaze at the face than the body region when inspecting individuals, and attended more to the body region in negative than in positive social interactions. Our study suggests that monkeys and humans share a similar pattern of role-sensitive, species- and context-dependent social attention, implying a homologous cognitive mechanism of social attention between rhesus macaques and humans

Evolution and Mirror Neurons. An Introduction to the Nature of Self-Consciousness

Self-consciousness is a product of evolution. Few people today disagree with the evolutionary history of humans. But the nature of self-consciousness is still to be explained, and the story of evolution has rarely been used as a framework for studies on consciousness during the 20th century. This last point may be due to the fact that modern study of consciousness came up at a time where dominant philosophical movements were not in favor of evolutionist theories (Cunningham 1996). Research on consciousness based on Phenomenology or on Analytic Philosophy has been mostly taking the characteristics of humans as starting points. Relatively little has been done with bottom-up approaches, using performances of animals as a simpler starting point to understand the generation of consciousness through evolution. But this status may be changing, thanks to new tools coming from recent discoveries in neurology. The discovery of mirror neurons about ten years ago (Gallese et al. 1996, Rizzolatti et al. 1996) has allowed the built up of new conceptual tools for the understanding of intersubjectivity within humans and non human primates (Gallese 2001, Hurley 2005). Studies in these fields are still in progress, with discussions on the level of applicability of this natural intersubjectivity to non human primates (Decety and Chaminade 2003). We think that these subject/conspecific mental relations made possible by mirror neurons can open new paths for the understanding of the nature of self-consciousness via an evolutionist bottom-up approach. We propose here a scenario for the build up of self-consciousness through evolution by a specific analysis of two steps of evolution: first step from simple living elements to non human primates comparable to chimpanzees, and second step from these non human primates to humans. We identify these two steps as representing the evolution from basic animal awareness to body self-awareness, and from body self-awareness to self-consciousness. (we consider that today non human primates are comparable to what were pre-human primates). We position body self-awareness as corresponding to the performance of mirror self recognition as identified with chimpanzees and orangutans (Gallup). We propose to detail and understand the content of this body self-awareness through a specific evolutionist build up process using the performances of mirror neurons and group life. We address the evolutionary step from body self-awareness to self-consciousness by complementing the recently proposed approach where self-consciousness is presented as a by-product of body self-awareness amplification via a positive feedback loop resulting of anxiety limitation (Menant 2004). The scenario introduced here for the build up of self-consciousness through evolution leaves open the question about the nature of phenomenal-consciousness (Block 2002). We plan to address this question later on with the help of the scenario made available here

Cold and Calculating

This nonfiction essay investigates the relationship between eye contact and power in different situations. It brings up the idea that animals and humans are less different than often thought to be, and how body language is transcendent. It uses this underlying theme to investigate the author’s changing relationship with her father