Differentiation in the defensive armor of the threespine stickleback, Gasterosteus aculeatus, is ... more Differentiation in the defensive armor of the threespine stickleback, Gasterosteus aculeatus, is caused by predator-driven divergent selection. Most studies considered armor traits related to swimming behavior, hence combining pre- and post-capture responses to gape-limited predators. Here, we focus exclusively on the defensive complex (DC), the post-capture predator defense. This complex consists of a series of bony elements surrounding the anterior part of the abdomen. Relaxation from predation pressure not only drives reduction of bony elements but is also expected to increase asymmetry in the DC. To test this hypothesis, we used four Austrian freshwater populations that differed distinctly in the formation of the DC. We found significant left–right asymmetries in the DC in the population with a distinctly reduced DC and, surprisingly, also in the population with a significantly enhanced DC. These populations occur in vastly different habitats (stream and lake) characterized by d...
Proceedings of the Royal Society B: Biological Sciences, 2021
The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasi... more The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasive biomarker for prenatal androgen exposure. It was found to be negatively correlated with handgrip strength (HGS) in men, but the evidence for women is mixed. Such studies in women call for increased detection sensitivity. The present study was designed to reduce potential confounding factors, especially age and ethnicity variation. We measured the digit ratios and HGS of 125 healthy women between 19 and 31 years of age from a remote region in Austria. 2D : 4D of both hands was significantly and negatively correlated with HGS ( n = 125, right hand: r = –0.255, p = 0.002, left hand: r = –0.206, p = 0.011). Size, direction and significance of correlation coefficients remained stable when statistically controlling for age, body weight, body height, body mass index or hours of exercise per week. This yields theory-consistent evidence that HGS and 2D : 4D are clearly associated in women—when...
Over evolutionary time, humans have developed a selective sensitivity to features in the human fa... more Over evolutionary time, humans have developed a selective sensitivity to features in the human face that convey information on sex, age, emotions, and intentions. This ability might not only be applied to our conspecifics nowadays, but also to other living objects (i.e., animals) and even to artificial structures, such as cars. To investigate this possibility, we asked people to report the characteristics, emotions, personality traits, and attitudes they attribute to car fronts, and we used geometric morphometrics (GM) and multivariate statistical methods to determine and visualize the corresponding shape information. Automotive features and proportions are found to covary with trait perception in a manner similar to that found with human faces. Emerging analogies are discussed. This study should have implications for both our understanding of our prehistoric psyche and its interrelation with the modern world.
ObjectivesPrevious research showed that male and female members of the Maasai from Northern Tanza... more ObjectivesPrevious research showed that male and female members of the Maasai from Northern Tanzania judge images of facial morphs calibrated to greater handgrip strength (HGS) higher on strength and attractiveness, but lower on aggressiveness than those calibrated to lower HGS. The accurate assessment of male physical strength from facial information may be adaptive as suggested by the evidence on health and fitness‐related benefits linked to high muscular strength.MethodsThis study extends previous work by obtaining European female (n = 220) and male (n = 51) assessments of HGS‐calibrated Maasai male faces. Participants rated five facial morphs for strength, attractiveness, and aggressiveness on computer screens.ResultsPerceived physical strength increased with morphs calibrated to higher HGS. The lowest and highest HGS morphs were judged lower in attractiveness than the others, and rated aggressiveness decreased in morphs calibrated to higher HGS.ConclusionsGiven the high similar...
The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasi... more The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasive biomarker for prenatal androgen exposure. It was found to be negatively correlated with handgrip strength (HGS) in men, but the evidence for women is mixed. Such studies in women call for increased detection sensitivity. The present study was designed to reduce potential confounding factors, especially age and ethnicity variation. We measured the digit ratios and HGS of 125 healthy women between 19 and 31 years of age from a remote region in Austria. 2D : 4D of both hands was significantly and negatively correlated with HGS (<i>n</i> = 125, right hand: <i>r</i> = –0.255, <i>p</i> = 0.002, left hand: <i>r</i> = –0.206, <i>p</i> = 0.011). Size, direction and significance of correlation coefficients remained stable when statistically controlling for age, body weight, body height, body mass index or hours of exercise per week. Th...
Research of the international PAR (PaleoAnthropological Research) team under the leadership of th... more Research of the international PAR (PaleoAnthropological Research) team under the leadership of the Institute for Anthropology, University of Vienna, started in 2000 and will be continued over the next years in the southern Afar Depression of Ethiopia. The Pliocene sedimentary ...
The study of human craniofacial variation exemplifi es general problems associated with the analy... more The study of human craniofacial variation exemplifi es general problems associated with the analysis of morphological plasticity that owe to the dependence of results on the methods by which phenotypic variation is quantifi ed. We suggest a defi nition of plasticity that does not subordinate the developmental to the evolutionary: A process model in which changes are not a function of any mean or average, but only of the current state. Geometric morphometrics, a toolkit for assessing and visualizing biological form and its covariates, avoids some of the traditional pitfalls by focusing directly on the analysis of the two-and three-dimensional coordinates of anatomical landmarks. We discuss its potential relevance to phenotypic and developmental plasticity research, as well as some of its limitations, and demonstrate two useful analyses: assessment of asymmetry, and appraisal of integration. We itemize some of our previous studies on causes (inbreeding, environmental circumstances, et...
Sex steroids are supposed to moderate the differences between male and female facial characterist... more Sex steroids are supposed to moderate the differences between male and female facial characteristics. Studies on women's preferences for male faces reported increased preferences for facial architecture developed under the influence of testosterone as this may indicate masculinity, dominance and social status. Recent research demonstrates that facial sexual dimorphism does not only develop at puberty but may be organized much earlier in ontogeny. However, the actual cause and timing of variation in facial shape due to sex-steroids remains speculative. This study uses data from Neave and colleagues who measured digit ratio (2D:4D) as a proxy to prenatal testosterone and also salivary testosterone samples in order to study differential effects of androgens on perceived male facial shape. Male facial shape was regressed upon 2D:4D ratio and circulating levels of testosterone by means of geometric morphometric methods. We found some evidence for opposite effects of early androgen ac...
Human physical attractiveness is supposed to reflect developmental stability (i.e. the ability of... more Human physical attractiveness is supposed to reflect developmental stability (i.e. the ability of individuals to maintain stable development of their morphology under a given environmental condition) and physiological status. Hence, evolutionary psychologists have suggested that appearance may not only reveal so called ‘honest signals ’ but even comprise a single ornament of mate value. However, it is still a matter of debate which physical features affect the ratings of female beauty, and whether these features are truly associated with as-pects of developmental and physiological status. Here we present morphometric data of images of faces and bodies from 92 women together with ratings of attractiveness by 60 men. A total of 101 somatometric landmarks were digitized as two-dimensional coordinates from three views: facial, front and back full-body view. These image sets were analyzed separately by means of geometric morphometric methodology (GMM). Attractiveness rat-ings of the face...
Humans' proneness to see faces even in inanimate structures such as cars has long been notice... more Humans' proneness to see faces even in inanimate structures such as cars has long been noticed, yet empirical evidence is scarce. To examine this tendency of anthropomorphism, participants were asked to compare specific features (such as the eyes) of a face and a car front presented next to each other. Eye movement patterns indicated on which visual information participants relied to solve the task and clearly revealed the perception of facial features in cars, such as headlights as eyes or grille as nose. Most importantly, a predominance of headlights was found in attracting and guiding people's gaze irrespective of the feature they were asked to compare--equivalent to the role of the eyes during face perception. This response to abstract configurations is interpreted as an adaptive bias of the respective inherent mechanism for face perception and is evolutionarily reasonable with regard to a "better safe than sorry" strategy.
We briefly and informally review the concepts of size, shape, and form and how they are estimated... more We briefly and informally review the concepts of size, shape, and form and how they are estimated in geometric morphometrics using Procrustes analysis. We demonstrate how deformation grids and reconstructed shapes or forms can be used as powerful tools to visualize shape and form dierences. Complexpatternsofindividualor groupdierencescanbestudiedeectiv elybyordinations of shape space or form space. Allometry, the statistical relationship between size and shape, is estimated in geometric morphometrics by regression of the Procrustes shape coordinates on centroid size. We illustrate these methods by an application to human face shape. We reveal shape cues to body size in the adult male face, partly resembling ontogenetic allometry. Facial allometry might thus be an important confounding factor in studies of face perception and human mate choice.
Previous research has documented associations of physical strength and facial morphology predomin... more Previous research has documented associations of physical strength and facial morphology predominantly in men of Western societies. Faces of strong men tend to be more robust, are rounder and have a prominent jawline compared with faces of weak men. Here, we investigate whether the morphometric patterns of strength-face relationships reported for members of industrialized societies can also be found in members of an African pastoralist society, the Maasai of Northern Tanzania. Handgrip strength (HGS) measures and facial photographs were collected from a sample of 185 men and 120 women of the Maasai in the Ngorongoro Conservation Area. In young-adults (20-29 years; n = 95) and mid-adults (30-50 years; n = 114), we digitized 71 somatometric landmarks and semilandmarks to capture variation in facial morphology and performed shape regressions of landmark coordinates upon HGS. Results were visualized in the form of thin-plate plate spline deformation grids and geometric morphometric morp...
Differentiation in the defensive armor of the threespine stickleback, Gasterosteus aculeatus, is ... more Differentiation in the defensive armor of the threespine stickleback, Gasterosteus aculeatus, is caused by predator-driven divergent selection. Most studies considered armor traits related to swimming behavior, hence combining pre- and post-capture responses to gape-limited predators. Here, we focus exclusively on the defensive complex (DC), the post-capture predator defense. This complex consists of a series of bony elements surrounding the anterior part of the abdomen. Relaxation from predation pressure not only drives reduction of bony elements but is also expected to increase asymmetry in the DC. To test this hypothesis, we used four Austrian freshwater populations that differed distinctly in the formation of the DC. We found significant left–right asymmetries in the DC in the population with a distinctly reduced DC and, surprisingly, also in the population with a significantly enhanced DC. These populations occur in vastly different habitats (stream and lake) characterized by d...
Proceedings of the Royal Society B: Biological Sciences, 2021
The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasi... more The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasive biomarker for prenatal androgen exposure. It was found to be negatively correlated with handgrip strength (HGS) in men, but the evidence for women is mixed. Such studies in women call for increased detection sensitivity. The present study was designed to reduce potential confounding factors, especially age and ethnicity variation. We measured the digit ratios and HGS of 125 healthy women between 19 and 31 years of age from a remote region in Austria. 2D : 4D of both hands was significantly and negatively correlated with HGS ( n = 125, right hand: r = –0.255, p = 0.002, left hand: r = –0.206, p = 0.011). Size, direction and significance of correlation coefficients remained stable when statistically controlling for age, body weight, body height, body mass index or hours of exercise per week. This yields theory-consistent evidence that HGS and 2D : 4D are clearly associated in women—when...
Over evolutionary time, humans have developed a selective sensitivity to features in the human fa... more Over evolutionary time, humans have developed a selective sensitivity to features in the human face that convey information on sex, age, emotions, and intentions. This ability might not only be applied to our conspecifics nowadays, but also to other living objects (i.e., animals) and even to artificial structures, such as cars. To investigate this possibility, we asked people to report the characteristics, emotions, personality traits, and attitudes they attribute to car fronts, and we used geometric morphometrics (GM) and multivariate statistical methods to determine and visualize the corresponding shape information. Automotive features and proportions are found to covary with trait perception in a manner similar to that found with human faces. Emerging analogies are discussed. This study should have implications for both our understanding of our prehistoric psyche and its interrelation with the modern world.
ObjectivesPrevious research showed that male and female members of the Maasai from Northern Tanza... more ObjectivesPrevious research showed that male and female members of the Maasai from Northern Tanzania judge images of facial morphs calibrated to greater handgrip strength (HGS) higher on strength and attractiveness, but lower on aggressiveness than those calibrated to lower HGS. The accurate assessment of male physical strength from facial information may be adaptive as suggested by the evidence on health and fitness‐related benefits linked to high muscular strength.MethodsThis study extends previous work by obtaining European female (n = 220) and male (n = 51) assessments of HGS‐calibrated Maasai male faces. Participants rated five facial morphs for strength, attractiveness, and aggressiveness on computer screens.ResultsPerceived physical strength increased with morphs calibrated to higher HGS. The lowest and highest HGS morphs were judged lower in attractiveness than the others, and rated aggressiveness decreased in morphs calibrated to higher HGS.ConclusionsGiven the high similar...
The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasi... more The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasive biomarker for prenatal androgen exposure. It was found to be negatively correlated with handgrip strength (HGS) in men, but the evidence for women is mixed. Such studies in women call for increased detection sensitivity. The present study was designed to reduce potential confounding factors, especially age and ethnicity variation. We measured the digit ratios and HGS of 125 healthy women between 19 and 31 years of age from a remote region in Austria. 2D : 4D of both hands was significantly and negatively correlated with HGS (<i>n</i> = 125, right hand: <i>r</i> = –0.255, <i>p</i> = 0.002, left hand: <i>r</i> = –0.206, <i>p</i> = 0.011). Size, direction and significance of correlation coefficients remained stable when statistically controlling for age, body weight, body height, body mass index or hours of exercise per week. Th...
Research of the international PAR (PaleoAnthropological Research) team under the leadership of th... more Research of the international PAR (PaleoAnthropological Research) team under the leadership of the Institute for Anthropology, University of Vienna, started in 2000 and will be continued over the next years in the southern Afar Depression of Ethiopia. The Pliocene sedimentary ...
The study of human craniofacial variation exemplifi es general problems associated with the analy... more The study of human craniofacial variation exemplifi es general problems associated with the analysis of morphological plasticity that owe to the dependence of results on the methods by which phenotypic variation is quantifi ed. We suggest a defi nition of plasticity that does not subordinate the developmental to the evolutionary: A process model in which changes are not a function of any mean or average, but only of the current state. Geometric morphometrics, a toolkit for assessing and visualizing biological form and its covariates, avoids some of the traditional pitfalls by focusing directly on the analysis of the two-and three-dimensional coordinates of anatomical landmarks. We discuss its potential relevance to phenotypic and developmental plasticity research, as well as some of its limitations, and demonstrate two useful analyses: assessment of asymmetry, and appraisal of integration. We itemize some of our previous studies on causes (inbreeding, environmental circumstances, et...
Sex steroids are supposed to moderate the differences between male and female facial characterist... more Sex steroids are supposed to moderate the differences between male and female facial characteristics. Studies on women's preferences for male faces reported increased preferences for facial architecture developed under the influence of testosterone as this may indicate masculinity, dominance and social status. Recent research demonstrates that facial sexual dimorphism does not only develop at puberty but may be organized much earlier in ontogeny. However, the actual cause and timing of variation in facial shape due to sex-steroids remains speculative. This study uses data from Neave and colleagues who measured digit ratio (2D:4D) as a proxy to prenatal testosterone and also salivary testosterone samples in order to study differential effects of androgens on perceived male facial shape. Male facial shape was regressed upon 2D:4D ratio and circulating levels of testosterone by means of geometric morphometric methods. We found some evidence for opposite effects of early androgen ac...
Human physical attractiveness is supposed to reflect developmental stability (i.e. the ability of... more Human physical attractiveness is supposed to reflect developmental stability (i.e. the ability of individuals to maintain stable development of their morphology under a given environmental condition) and physiological status. Hence, evolutionary psychologists have suggested that appearance may not only reveal so called ‘honest signals ’ but even comprise a single ornament of mate value. However, it is still a matter of debate which physical features affect the ratings of female beauty, and whether these features are truly associated with as-pects of developmental and physiological status. Here we present morphometric data of images of faces and bodies from 92 women together with ratings of attractiveness by 60 men. A total of 101 somatometric landmarks were digitized as two-dimensional coordinates from three views: facial, front and back full-body view. These image sets were analyzed separately by means of geometric morphometric methodology (GMM). Attractiveness rat-ings of the face...
Humans' proneness to see faces even in inanimate structures such as cars has long been notice... more Humans' proneness to see faces even in inanimate structures such as cars has long been noticed, yet empirical evidence is scarce. To examine this tendency of anthropomorphism, participants were asked to compare specific features (such as the eyes) of a face and a car front presented next to each other. Eye movement patterns indicated on which visual information participants relied to solve the task and clearly revealed the perception of facial features in cars, such as headlights as eyes or grille as nose. Most importantly, a predominance of headlights was found in attracting and guiding people's gaze irrespective of the feature they were asked to compare--equivalent to the role of the eyes during face perception. This response to abstract configurations is interpreted as an adaptive bias of the respective inherent mechanism for face perception and is evolutionarily reasonable with regard to a "better safe than sorry" strategy.
We briefly and informally review the concepts of size, shape, and form and how they are estimated... more We briefly and informally review the concepts of size, shape, and form and how they are estimated in geometric morphometrics using Procrustes analysis. We demonstrate how deformation grids and reconstructed shapes or forms can be used as powerful tools to visualize shape and form dierences. Complexpatternsofindividualor groupdierencescanbestudiedeectiv elybyordinations of shape space or form space. Allometry, the statistical relationship between size and shape, is estimated in geometric morphometrics by regression of the Procrustes shape coordinates on centroid size. We illustrate these methods by an application to human face shape. We reveal shape cues to body size in the adult male face, partly resembling ontogenetic allometry. Facial allometry might thus be an important confounding factor in studies of face perception and human mate choice.
Previous research has documented associations of physical strength and facial morphology predomin... more Previous research has documented associations of physical strength and facial morphology predominantly in men of Western societies. Faces of strong men tend to be more robust, are rounder and have a prominent jawline compared with faces of weak men. Here, we investigate whether the morphometric patterns of strength-face relationships reported for members of industrialized societies can also be found in members of an African pastoralist society, the Maasai of Northern Tanzania. Handgrip strength (HGS) measures and facial photographs were collected from a sample of 185 men and 120 women of the Maasai in the Ngorongoro Conservation Area. In young-adults (20-29 years; n = 95) and mid-adults (30-50 years; n = 114), we digitized 71 somatometric landmarks and semilandmarks to capture variation in facial morphology and performed shape regressions of landmark coordinates upon HGS. Results were visualized in the form of thin-plate plate spline deformation grids and geometric morphometric morp...
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Papers by Katrin Schaefer