Left, right or both? Estimating and improving accuracy of one‐side‐only geometric morphometric analyses of cranial variation

Procrustes-based geometric morphometric analyses of bilaterally symmetric structures are often performed using only one side. This is particularly common in studies of cranial variation in mammals and other vertebrates. When one is not interested in quantifying asymmetry, landmarking one side, instead of both, reduces the number of variables as well as the time and costs of data collection. It is assumed that the loss of information in the other half, on which landmarks are not digitized, is negligible, but this has seldom been tested. Using 10 samples of mammalian crania and a total of more than 500 specimens, and five different landmark configurations, I demonstrate that this assumption is indeed easily met for size. For shape, in contrast, one-side landmarking has potentially more severe consequences on the estimates of similarity relationships in a sample. In this respect, microevolutionary analyses of small differences are particularly affected, whereas macroevolutionary studies are fairly robust. In almost all instances, however, a simple preliminary operation improves accuracy by making one-side-only shape data more similar to those obtained by landmarking both sides. The same operation also makes estimates of allometry more accurate and improves the visualization. This operation consists in estimating the missing side by a mirror reflection of bilateral landmarks. In the Supporting Information, I exemplify how this can be easily done using free user-friendly software. I also provide an example data set for readers to repeat and learn the steps of this simple procedure

Piracy strikes back on Lake Maggiore (Northen Italy): first report of Common Merganser Mergus merganser kleptoparasitizing Great Crested grebe Podiceps cristatus

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A 'long-fuse domestication' of the horse? Tooth shape suggests explosive change in modern breeds compared with extinct populations and living Przewalski's horses

Archaeological and molecular data suggest that horses were domesticated comparatively recently, the genetic evidence indicating that this was from several maternal haplotypes but only a single paternal one. However, although central to our understanding of how humans and environmental conditions shaped animals during domestication, the phenotypic changes associated with this idiosyncratic domestication process remain unclear. Using geometric morphometrics on a sample of horse teeth including Pleistocene wild horses, modern Icelandic and Thoroughbred domestic horses, Przewalski’s wild horses of recent age and domestic horses of different ages through the Holocene, we show that, despite variations in size likely related to allometry (changes to bone size in proportion to body size), natural and artificial selective pressures and geographic and temporal heterogeneity, the shape of horse teeth has changed surprisingly little over thousands of years across Eurasia: the shapes of the premolars of prehistoric and historic domestic horses largely resemble those of Pleistocene and recent wild horses. However, this changed dramatically after the end of the Iron Age with an explosive increase in the pace and scale of variation in the past two millennia, ultimately resulting in a twofold jump in the magnitude of shape divergence in modern breeds. Our findings indicate that the pace of change during domestication may vary even within the same structure with shape, but not size, suggesting a ‘long-fuse’ model of phenotypic modification, where an initial lengthy period of invariance is followed by an explosive increase in the phenotypic change. These observations support a testable model that is applicable to other traits and species and add a new layer of complexity to the study of interactions between humans and the organisms they domesticated. Funding was provided to GB from the Leverhulme Trust project grant scheme (F/09 757/B) and to KS and AC from the Lang Fund for Human-Environmental Anthropology, Department of Anthropology, Stanford.This is the author accepted manuscript. The final version is available from Sage via http://dx.doi.org/10.1177/095968361663843

Your place or mine:Shared sensory experiences elicit a remapping of peripersonal space

Our perceptual systems integrate multisensory information about objects that are close to our bodies, which allow us to respond quickly and appropriately to potential threats, as well as act upon and manipulate useful tools. Intriguingly, the representation of this area close to our body, known as the multisensory 'peripersonal space' (PPS), can expand or contract during social interactions. However, it is not yet known how different social interactions can alter the representation of PPS. In particular, shared sensory experiences, such as those elicited by bodily illusions such as the enfacement illusion, can induce feelings of ownership over the other's body which has also been shown to increase the remapping of the other's sensory experiences onto our own bodies. The current study investigated whether such shared sensory experiences between two people induced by the enfacement illusion could alter the way PPS was represented, and whether this alteration could be best described as an expansion of one's own PPS towards the other or a remapping of the other's PPS onto one's own. An audio-tactile integration task allowed us to measure the extent of the PPS before and after a shared sensory experience with a confederate. Our results showed a clear increase in audio-tactile integration in the space close to the confederate's body after the shared experience. Importantly, this increase did not extend across the space between participant and confederate, as would be expected if the participant's PPS had expanded. Thus, the pattern of results is more consistent with a partial remapping of the confederate's PPS onto the participant's own PPS. These results have important consequences for our understanding of interpersonal space during different kinds of social interactions. (C) 2014 Elsevier Ltd. All rights reserved

Can you feel the body that you see? On the relationship between interoceptive accuracy and body image

Interoception and exteroception for body signals are two different ways of perceiving the self: the first from within, the second from outside. We investigated the relationship between Interoceptive Accuracy (IAcc) and external perception of the body and we tested if seeing the body from an external perspective can affect IAcc. Fifty-two healthy female subjects performed a standard heartbeat perception task to assess the IAcc, before and after the Body Image Revealer (BIR), which is a body perception task designed to assess the different aspects of body-image. The performance of the lower IAcc group in the heartbeat perception task significantly improved after the exteroceptive task. These findings highlight the relations between interoceptive and exteroceptive body-representations, supporting the view that these two kinds of awareness are linked and interact with each other