The Scent of Symmetry: A Human Sex Pheromone that Signals Fitness?

A previous study by the authors showed that the body scent of men who have greater body bilateral symmetry is rated as more attractive by normally ovulating (non-pill-using) women during the period of highest fertility based on day within the menstrual cycle. Women in low-fertility phases of the cycle and women using hormone-based contraceptives do not show this pattern. The current study replicated these findings with a larger sample and statistically controlled for men's hygiene and other factors that were not controlled in the first study. The current study also examined women's scent attractiveness to men and found no evidence that men prefer the scent of symmetric women. We propose that the scent of symmetry is an honest signal of phenotypic and genetic quality in the human male, and chemical candidates are discussed. In both sexes, facial attractiveness (as judged from photos) appears to predict body scent attractiveness to the opposite sex. Women's preference for the scent associated with men's facial attractiveness is greatest when their fertility is highest across the menstrual cycle. The results overall suggest that women have an evolved preference for sires with good genes.     

Do Bodily Expressions Compete with Facial Expressions? Time Course of Integration of Emotional Signals from the Face and the Body

The decoding of social signals from nonverbal cues plays a vital role in the social interactions of socially gregarious animals such as humans. Because nonverbal emotional signals from the face and body are normally seen together, it is important to investigate the mechanism underlying the integration of emotional signals from these two sources. We conducted a study in which the time course of the integration of facial and bodily expressions was examined via analysis of event-related potentials (ERPs) while the focus of attention was manipulated. Distinctive integrating features were found during multiple stages of processing. In the first stage, threatening information from the body was extracted automatically and rapidly, as evidenced by enhanced P1 amplitudes when the subjects viewed compound face-body images with fearful bodies compared with happy bodies. In the second stage, incongruency between emotional information from the face and the body was detected and captured by N2. Incongruent compound images elicited larger N2s than did congruent compound images. The focus of attention modulated the third stage of integration. When the subjects'' attention was focused on the face, images with congruent emotional signals elicited larger P3s than did images with incongruent signals, suggesting more sustained attention and elaboration of congruent emotional information extracted from the face and body. On the other hand, when the subjects'' attention was focused on the body, images with fearful bodies elicited larger P3s than did images with happy bodies, indicating more sustained attention and elaboration of threatening information from the body during evaluative processes.     

The Ashley Treatment: Improving Quality of Life or Infringing Dignity and Rights?

The ‘Ashley treatment’ (growth attenuation, removal of the womb and breasts buds of a severely disabled child) has raised much ethical controversy. This article starts from the observation that this debate suffers from a lack of careful philosophical analysis which is essential for an ethical assessment. I focus on two central arguments in the debate, namely an argument defending the treatment based on quality of life and an argument against the treatment based on dignity and rights. My analysis raises doubts as to whether these arguments, as they stand in the debate, are philosophically robust. I reconstruct what form good arguments for and against the treatment should take and which assumptions are needed to defend the according positions. Concerning quality of life (Section 2), I argue that to make a discussion about quality of life possible, it needs to be clear which particular conception of the good life is employed. This has not been sufficiently clear in the debate. I fill this lacuna. Regarding rights and dignity (section 3), I show that there is a remarkable absence of references to general philosophical theories of rights and dignity in the debate about the Ashley treatment. Consequently, this argument against the treatment is not sufficiently developed. I clarify how such an argument should proceed. Such a detailed analysis of arguments is necessary to clear up some confusions and ambiguities in the debate and to shed light on the dilemma that caretakers of severely disabled children face.     

Does My Face FIT?: A Face Image Task Reveals Structure and Distortions of Facial Feature Representation

Despite extensive research on face perception, few studies have investigated individuals’ knowledge about the physical features of their own face. In this study, 50 participants indicated the location of key features of their own face, relative to an anchor point corresponding to the tip of the nose, and the results were compared to the true location of the same individual’s features from a standardised photograph. Horizontal and vertical errors were analysed separately. An overall bias to underestimate vertical distances revealed a distorted face representation, with reduced face height. Factor analyses were used to identify separable subconfigurations of facial features with correlated localisation errors. Independent representations of upper and lower facial features emerged from the data pattern. The major source of variation across individuals was in representation of face shape, with a spectrum from tall/thin to short/wide representation. Visual identification of one’s own face is excellent, and facial features are routinely used for establishing personal identity. However, our results show that spatial knowledge of one’s own face is remarkably poor, suggesting that face representation may not contribute strongly to self-awareness.     

Does Ethnicity Influence Body-Size Preference? A Comparison of Body Image and Body Size

Objective: Obesity is most common in the United States among women of ethnic minority groups (black and Hispanic). Researchers have hypothesized that these subcultures are more accepting of overweight figures. The purpose of this study was to examine body image and body size assessments in a large community sample of men and women. Research Methods and Procedures: Participants were 801 women and 428 men: 23% Asian, 45% Hispanic, 17% black, and 15% white. The figure rating scale was used to rate: body dissatisfaction, attractive male and female shapes, acceptable female size, and perceptions of underweight to obese female figures. Results: Controlling for age, education, and body weight, no ethnic differences were found for men. Asian women reported less body dissatisfaction than the other groups. Women were more dissatisfied with their size than men and chose thinner female figures as attractive and acceptable. Discussion: Ethnicity, independent of age, education, and body weight, does not influence preference for female and male shapes or tolerance for obesity.     

The Dartmouth Database of Children’s Faces: Acquisition and Validation of a New Face Stimulus Set

Facial identity and expression play critical roles in our social lives. Faces are therefore frequently used as stimuli in a variety of areas of scientific research. Although several extensive and well-controlled databases of adult faces exist, few databases include children’s faces. Here we present the Dartmouth Database of Children’s Faces, a set of photographs of 40 male and 40 female Caucasian children between 6 and 16 years-of-age. Models posed eight facial expressions and were photographed from five camera angles under two lighting conditions. Models wore black hats and black gowns to minimize extra-facial variables. To validate the images, independent raters identified facial expressions, rated their intensity, and provided an age estimate for each model. The Dartmouth Database of Children’s Faces is freely available for research purposes and can be downloaded by contacting the corresponding author by email.     

The principles and practice of human evolution research: Are we asking questions that can be answered?

The research agenda of paleoanthropology involves many topics and methodologies. Fossil specimens are allocated to species, and those species are assigned to the hominin clade. After that we want to know how they are related to each other, what they ate, how much they weighed, how smart they were, etc. We also want to know about the origin of particular attributes of hominins, such as our delayed growth and development, bipedalism, and language. The data available to answer these complex questions are confounded by fragmentary fossil specimens, small sample sizes, limited opportunities for controlled experimentation, and the inherent limitations of historical data. Also, because many traits are effectively unique to hominins, even observational comparative studies are inevitably limited in what they can tell us, if not impossible to conduct. We explore how these limitations should, but often do not, constrain the questions that paleoanthropologists should attempt to answer.     

The Body as Gift,Resource or Commodity? Heidegger and the Ethics of Organ Transplantation

Three metaphors appear to guide contemporary thinking about organ transplantation. Although the gift is the sanctioned metaphor for donating organs, the underlying perspective from the side of the state, authorities and the medical establishment often seems to be that the body shall rather be understood as a resource. The acute scarcity of organs, which generates a desperate demand in relation to a group of potential suppliers who are desperate to an equal extent, leads easily to the gift’s becoming, in reality, not only a resource, but also a commodity. In this paper, the claim is made that a successful explication of the gift metaphor in the case of organ transplantation and a complementary defence of the ethical primacy of the giving of organs need to be grounded in a philosophical anthropology which considers the implications of embodiment in a different and more substantial way than is generally the case in contemporary bioethics. I show that Heidegger’s phenomenology offers such an alternative, with the help of which we can understand why body parts could and, indeed, under certain circumstances, should be given to others in need, but yet are neither resources nor properties to be sold. The phenomenological exploration in question is tied to fundamental questions about what kind of relationship we have to our own bodies, as well as about what kind of relationship we have to each other as human beings sharing the same being-in-the-world as embodied creatures.     

The Positional Quality of Life and Death: A Theory of Human–Animal Relations in Animism

ABSTRACT

This article examines human–animal relations in animism. Ethnographies of indigenous peoples in the Americas, Asia, and Africa are compared in order to provide a basic sketch of the remarkable consistency of animism across the world. A central feature that recurs time and again is the positional quality of life and death. That is, life and death are not conceived of as inherent properties but as changeable positions. This is why indigenous hunters, shamans, and diviners temporarily “die” when they participate in the specific rites or cults associated with their respective endeavors. Such metamorphoses of the living into the dead are crucial to understand how hunters engage with their prey, shamans mobilize their animal-helpers, and honey collectors approach their bees. At the same time, these different activities involve the transformation of humans into animals. Chachi bird stalkers and Uduk antelope hunters identify themselves with their quarry, Navajo medicine men and Ainu shamans shape-change into their animallike adversaries, while Batek mourners may adopt a tiger-form. At first sight, such simultaneous metamorphoses (from the living into the dead and from humans into animals) may seem contradictory. Yet, this apparent inconsistency disappears if one realizes that the modern notion of wildlife cannot be applied to animism. I show that the monkeys, deer, whales, tigers, and elephants that indigenous hunters and shamans deal with must be understood as “wild-dead” rather than as wildlife. These various animals are palpable representatives of an expanded realm of death which—I suggest—is characteristic of all forms of animism. In this context, being animate is not sufficient to be considered “alive.”     

Why the Long Face? The Mechanics of Mandibular Symphysis Proportions in Crocodiles

Background

Crocodilians exhibit a spectrum of rostral shape from long snouted (longirostrine), through to short snouted (brevirostrine) morphologies. The proportional length of the mandibular symphysis correlates consistently with rostral shape, forming as much as 50% of the mandible’s length in longirostrine forms, but 10% in brevirostrine crocodilians. Here we analyse the structural consequences of an elongate mandibular symphysis in relation to feeding behaviours.

Methods/Principal Findings

Simple beam and high resolution Finite Element (FE) models of seven species of crocodile were analysed under loads simulating biting, shaking and twisting. Using beam theory, we statistically compared multiple hypotheses of which morphological variables should control the biomechanical response. Brevi- and mesorostrine morphologies were found to consistently outperform longirostrine types when subject to equivalent biting, shaking and twisting loads. The best predictors of performance for biting and twisting loads in FE models were overall length and symphyseal length respectively; for shaking loads symphyseal length and a multivariate measurement of shape (PC1– which is strongly but not exclusively correlated with symphyseal length) were equally good predictors. Linear measurements were better predictors than multivariate measurements of shape in biting and twisting loads. For both biting and shaking loads but not for twisting, simple beam models agree with best performance predictors in FE models.

Conclusions/Significance

Combining beam and FE modelling allows a priori hypotheses about the importance of morphological traits on biomechanics to be statistically tested. Short mandibular symphyses perform well under loads used for feeding upon large prey, but elongate symphyses incur high strains under equivalent loads, underlining the structural constraints to prey size in the longirostrine morphotype. The biomechanics of the crocodilian mandible are largely consistent with beam theory and can be predicted from simple morphological measurements, suggesting that crocodilians are a useful model for investigating the palaeobiomechanics of other aquatic tetrapods.