scholarly journals Sexual Selection and Human Breast Morphology

2021 ◽  
Author(s):  
◽  
Melanie Duncan

<p>Human females, uniquely among primates, develop prominent breasts during puberty, well before reproduction occurs. Adipose tissue in breasts forms part of the "gynoid"  fat distribution, involving the hips, thighs, buttocks and breasts of women. Breasts are thus characterised as secondary sexual characteristics, and their evolution may be due, at least in part, to the effects of sexual selection. This partial reversal of the usual pattern of male adornment may be related to high paternal care in humans. Breast morphology is complex, so that women vary not only in the size and shape of their breasts, but also in the size, shape and pigmentation of their areolae and nipples. These traits change with reproductive status and age. Breasts are more prone to fluctuating asymmetry than many other features of human anatomy and such asymmetry may be closely related to some measures of reproductive success. This thesis used digitally altered images to investigate the impact of morphological changes on perceptions of attractiveness and other qualities. Study 1 investigated the impact of four breast sizes and three areola colours on the perceptions of two hundred participants. Breast size significantly impacted all ratings. Attractiveness and health ratings were maximised at the intermediate breast size for the lightest and original coloured areola, and at the largest breast size for the darkest areola. Ratings of nurturance, sexual maturity and estimates of age increased stepwise from the images with undeveloped breasts to the images with the largest breasts. Areola colour interacted with breast size. Darker areola were judged less attractive, less healthy and less nurturing when paired with small or intermediate breasts, but increased these ratings when paired with large breasts. There was no strong effect of areola colour on ratings of images with undeveloped breasts or on ratings of sexual maturity and age. Study 2 investigated the effect of breast asymmetry on attractiveness and health ratings using data provided by two hundred participants. Increasing levels of asymmetry, created by modifying one breast to increase the apparent volume (four levels from 102.5% to 110% of the original) or position (four levels from 1%-4% of the length of the image) resulted in progressively lower ratings. The differences in ratings between the images with extreme levels in asymmetry (107.5% vs 110% and 3% vs 4%) were smaller. Images that had been modified in the models left (and so seen on viewer's right side) were given higher ratings than those modified identically but on the other side. This may be an expression of a phenomena known as pseudoneglect, where people appear to attend more to the left. In Study 3, a diverse selection of images, taken from previously published reports on human breast morphology and attractiveness, were compiled as a single questionnaire and shown to 37 participants. The purpose of this pilot study was to assess the impact of different image types on ratings of attractiveness and health. Photographic images were rated higher than line drawings or silhouettes. Photographs may be more ecologically valid, as they are more realistic and can be tailored to match the study population. The results presented in this thesis indicate that variations in human breast size, areola colour and breast asymmetry have measurable effects on the perceptions (of both sexes) of attractiveness and health. Breast size also has significant impacts on perceptions of nurturance, reproductive status and age, whereas areola colour has less effect on these ratings. Questionnaire studies employing photographs are likely to be more effective than more stylised images. Morphological changes in the human breast may signal mate value and fertility and therefore may have been subject to sexual selection, as well as natural selection, during human evolution.</p>

2021 ◽  
Author(s):  
◽  
Melanie Duncan

<p>Human females, uniquely among primates, develop prominent breasts during puberty, well before reproduction occurs. Adipose tissue in breasts forms part of the "gynoid"  fat distribution, involving the hips, thighs, buttocks and breasts of women. Breasts are thus characterised as secondary sexual characteristics, and their evolution may be due, at least in part, to the effects of sexual selection. This partial reversal of the usual pattern of male adornment may be related to high paternal care in humans. Breast morphology is complex, so that women vary not only in the size and shape of their breasts, but also in the size, shape and pigmentation of their areolae and nipples. These traits change with reproductive status and age. Breasts are more prone to fluctuating asymmetry than many other features of human anatomy and such asymmetry may be closely related to some measures of reproductive success. This thesis used digitally altered images to investigate the impact of morphological changes on perceptions of attractiveness and other qualities. Study 1 investigated the impact of four breast sizes and three areola colours on the perceptions of two hundred participants. Breast size significantly impacted all ratings. Attractiveness and health ratings were maximised at the intermediate breast size for the lightest and original coloured areola, and at the largest breast size for the darkest areola. Ratings of nurturance, sexual maturity and estimates of age increased stepwise from the images with undeveloped breasts to the images with the largest breasts. Areola colour interacted with breast size. Darker areola were judged less attractive, less healthy and less nurturing when paired with small or intermediate breasts, but increased these ratings when paired with large breasts. There was no strong effect of areola colour on ratings of images with undeveloped breasts or on ratings of sexual maturity and age. Study 2 investigated the effect of breast asymmetry on attractiveness and health ratings using data provided by two hundred participants. Increasing levels of asymmetry, created by modifying one breast to increase the apparent volume (four levels from 102.5% to 110% of the original) or position (four levels from 1%-4% of the length of the image) resulted in progressively lower ratings. The differences in ratings between the images with extreme levels in asymmetry (107.5% vs 110% and 3% vs 4%) were smaller. Images that had been modified in the models left (and so seen on viewer's right side) were given higher ratings than those modified identically but on the other side. This may be an expression of a phenomena known as pseudoneglect, where people appear to attend more to the left. In Study 3, a diverse selection of images, taken from previously published reports on human breast morphology and attractiveness, were compiled as a single questionnaire and shown to 37 participants. The purpose of this pilot study was to assess the impact of different image types on ratings of attractiveness and health. Photographic images were rated higher than line drawings or silhouettes. Photographs may be more ecologically valid, as they are more realistic and can be tailored to match the study population. The results presented in this thesis indicate that variations in human breast size, areola colour and breast asymmetry have measurable effects on the perceptions (of both sexes) of attractiveness and health. Breast size also has significant impacts on perceptions of nurturance, reproductive status and age, whereas areola colour has less effect on these ratings. Questionnaire studies employing photographs are likely to be more effective than more stylised images. Morphological changes in the human breast may signal mate value and fertility and therefore may have been subject to sexual selection, as well as natural selection, during human evolution.</p>


2021 ◽  
Author(s):  
◽  
Barnaby James Wyld Dixson

<p>Charles Darwin proposed in The Descent of Man and Selection in Relation to Sex (1871) that traits which improve reproductive success, such as sexually attractive adornments, or weaponry that enhances fighting potential, have been selected for during the course of evolution. The field of evolutionary psychology has revitalized Darwin's hypotheses of sexual selection and human evolution through integrating the fields of anthropology, biology and psychology. In this thesis I investigate the potential for sexual selection to have acted upon sexual dimorphism in body composition and secondary sexual adornments in women and men. In women, body fat accumulation around the hips, buttocks and thighs can be measured using the waist-to-hip ratio (WHR). Female body fat and body weight are critical as energy reserves for gestation, pregnancy and lactation. Female body shape, body weight and breast morphology have been implicated in male judgments of female physical attractiveness. Men from New Zealand (NZ), China, Samoa and the highlands of Papua New Guinea (PNG) rated images of women with low WHRs as most attractive, independent of changes in body weight. In studies of male preferences for female breast morphology, married men from NZ, Samoa and PNG preferred large breasts whereas unmarried men preferred medium-sized breasts. Darkly- and medium-pigmented areolae were preferred in each culture, as were symmetrical breasts. However, male preferences for female areolar size varied considerably across these cultures. Eye-tracking techniques were used to measure attention to morphological traits as men made attractiveness judgments of female images that varied in WHR and breast morphology. In studies using full-length female images that varied in WHR and breast size, men look most often and for longer at the regions of female physique in which fat deposits are greatest (i.e. the breasts followed by the waist). However, attractiveness judgments were driven primarily by WHR rather than breast size. In eye-tracking studies using female torsos as stimuli, men looked most often and for longest at the breasts and areolae, irrespective of differences in breast size and areolar pigmentation. Men rated large and medium size breasts, and medium and darkly pigmented areolae as most attractive. These eye-tracking studies show a possible discordance in male visual attention for morphological traits that appear to drive attractiveness decisions. However, when men were shown full-length images of women posed in back-view as well as in front-view there were significant differences in their viewing patterns. Men spent more time looking at the midriff region of back-posed images than front-posed images and, irrespective of body-pose, rated images with low WHRs as most sexually attractive. Darwin suggested that the human male beard evolved via female choice as a highly attractive secondary sexual adornment. Other authors have proposed that the beard may augment aggressive displays and enhance perceptions of social dominance among males. To test these hypotheses I developed a new questionnaire that integrated facial expressions with the presence or absence of the beard. These questionnaires were administered in NZ and Samoa. The presence of a beard augmented male perceptions of aggressive facial expressions in Samoa and NZ. However, women in these cultures rated faces without beards as more attractive than bearded men. Men and women in both cultures rated bearded men as looking older and as having higher social status. The findings suggest that the beard plays a stronger role in intra-sexual competition rather than inter-sexual mate choice.</p>


Author(s):  
Nicholas Moellhoff ◽  
Chiara Kandelhardt ◽  
Denis Ehrl ◽  
Lukas Kohler ◽  
Konstantin Koban ◽  
...  

Abstract Background The objective assessment of beauty is challenging and subject to current research efforts. Recently, a new means of objectively determining the aesthetic appeal of body features has been investigated by analyzing gaze patterns and eye movements. Objectives The objective of this study was to assess differences in observers’ gaze patterns presented with standardized 3-dimensional images with different degrees of breast asymmetry using objective eye-tracking technology. Methods A total of 83 Caucasian study participants with a mean age of 38.60 (19.8) years were presented with 5 images depicting varying degrees of breast symmetry. In addition to the assessment of eye movements, participants were asked to rate the aesthetic appeal and the asymmetry of the breasts on a 5-point Likert scale. Results Overall, the data show that participants rating of the breasts’ aesthetic appeal was inversely related to the level of asymmetry. Time until fixation was shortest for the image depicting the greatest breast asymmetry (50 cc) with 0.77 (0.7), p &lt;0.001. In addition, the mammary region was also viewed longest in this image with 3.76 (0.5) seconds, p &lt; 0.001. A volume difference of 35 cc between breasts deflected the observers’ gaze significantly toward the larger of the asymmetrical breasts, p&lt;0.001. Conclusions Surgeons should focus on symmetrical breast volume (ie, differences &lt; 35 cc between breasts) to avoid noticeable asymmetry with regard to breast size.


2021 ◽  
Author(s):  
◽  
Barnaby James Wyld Dixson

<p>Charles Darwin proposed in The Descent of Man and Selection in Relation to Sex (1871) that traits which improve reproductive success, such as sexually attractive adornments, or weaponry that enhances fighting potential, have been selected for during the course of evolution. The field of evolutionary psychology has revitalized Darwin's hypotheses of sexual selection and human evolution through integrating the fields of anthropology, biology and psychology. In this thesis I investigate the potential for sexual selection to have acted upon sexual dimorphism in body composition and secondary sexual adornments in women and men. In women, body fat accumulation around the hips, buttocks and thighs can be measured using the waist-to-hip ratio (WHR). Female body fat and body weight are critical as energy reserves for gestation, pregnancy and lactation. Female body shape, body weight and breast morphology have been implicated in male judgments of female physical attractiveness. Men from New Zealand (NZ), China, Samoa and the highlands of Papua New Guinea (PNG) rated images of women with low WHRs as most attractive, independent of changes in body weight. In studies of male preferences for female breast morphology, married men from NZ, Samoa and PNG preferred large breasts whereas unmarried men preferred medium-sized breasts. Darkly- and medium-pigmented areolae were preferred in each culture, as were symmetrical breasts. However, male preferences for female areolar size varied considerably across these cultures. Eye-tracking techniques were used to measure attention to morphological traits as men made attractiveness judgments of female images that varied in WHR and breast morphology. In studies using full-length female images that varied in WHR and breast size, men look most often and for longer at the regions of female physique in which fat deposits are greatest (i.e. the breasts followed by the waist). However, attractiveness judgments were driven primarily by WHR rather than breast size. In eye-tracking studies using female torsos as stimuli, men looked most often and for longest at the breasts and areolae, irrespective of differences in breast size and areolar pigmentation. Men rated large and medium size breasts, and medium and darkly pigmented areolae as most attractive. These eye-tracking studies show a possible discordance in male visual attention for morphological traits that appear to drive attractiveness decisions. However, when men were shown full-length images of women posed in back-view as well as in front-view there were significant differences in their viewing patterns. Men spent more time looking at the midriff region of back-posed images than front-posed images and, irrespective of body-pose, rated images with low WHRs as most sexually attractive. Darwin suggested that the human male beard evolved via female choice as a highly attractive secondary sexual adornment. Other authors have proposed that the beard may augment aggressive displays and enhance perceptions of social dominance among males. To test these hypotheses I developed a new questionnaire that integrated facial expressions with the presence or absence of the beard. These questionnaires were administered in NZ and Samoa. The presence of a beard augmented male perceptions of aggressive facial expressions in Samoa and NZ. However, women in these cultures rated faces without beards as more attractive than bearded men. Men and women in both cultures rated bearded men as looking older and as having higher social status. The findings suggest that the beard plays a stronger role in intra-sexual competition rather than inter-sexual mate choice.</p>


Author(s):  
M. S. Bugaeva ◽  
O. I. Bondarev ◽  
N. N. Mikhailova ◽  
L. G. Gorokhova

Introduction. The impact on the body of such factors of the production environment as coal-rock dust and fluorine compounds leads to certain shift s in strict indicators of homeostasis at the system level. Maintaining the relative constancy of the internal environment of the body is provided by the functional consistency of all organs and systems, the leading of which is the liver. Organ repair plays a crucial role in restoring the structure of genetic material and maintaining normal cell viability. When this mechanism is damaged, the compensatory capabilities of the organ are disrupted, homeostasis is disrupted at the cellular and organizational levels, and the development of the main pathological processes is noted.The aim of the study is to compare the morphological mechanisms of maintaining structural homeostasis of the liver in the dynamics of the impact on the body of coal-rock dust and sodium fluoride.Materials and methods. Experimental studies were conducted on adult white male laboratory rats. Features of morphological mechanisms for maintaining structural homeostasis of the liver in the dynamics of exposure to coal-rock dust and sodium fluoride were studied on experimental models of pneumoconiosis and fluoride intoxication. For histological examination in experimental animals, liver sampling was performed after 1, 3, 6, 9, 12 weeks of the experiment.Results. The specificity of morphological changes in the liver depending on the harmful production factor was revealed. It is shown that chronic exposure to coal-rock dust and sodium fluoride is characterized by the development of similar morphological changes in the liver and its vessels from the predominance of the initial compensatory-adaptive to pronounced violations of the stromal and parenchymal components. Long-term inhalation of coal-rock dust at 1–3 weeks of seeding triggers adaptive mechanisms in the liver in the form of increased functional activity of cells, formation of double-core hepatocytes, activation of immunocompetent cells and endotheliocytes, ensuring the preservation of the parenchyma and the general morphostructure of the organ until the 12th week of the experiment. Exposure to sodium fluoride leads to early disruption of liver compensatory mechanisms and the development of dystrophic changes in the parenchyma with the formation of necrosis foci as early as the 6th week of the experiment.Conclusions. The study of mechanisms for compensating the liver structure in conditions of long-term exposure to coal-rock dust and sodium fluoride, as well as processes that indicate their failure, and the timing of their occurrence, is of theoretical and practical importance for developing recommendations for the timely prevention and correction of pathological conditions developing in employees of the aluminum and coal industry.The authors declare no conflict of interests.


2018 ◽  
Vol 16 (2) ◽  
pp. 127-137
Author(s):  
Paula Sofia Coutinho Medeiros ◽  
Ana Lúcia Marques Batista de Carvalho ◽  
Cristina Ruano ◽  
Juan Carlos Otero ◽  
Maria Paula Matos Marques

Background: The impact of the ubiquitous dietary phenolic compound p-coumaric acid on human breast cancer cells was assessed, through a multidisciplinary approach: Combined biological assays for cytotoxicity evaluation and biochemical profiling by Raman microspectroscopic analysis in cells. </P><P> Methods: Para-coumaric acid was shown to exert in vitro chemoprotective and antitumor activities, depending on the concentration and cell line probed: a significant anti-invasive ability was detected for the triple-negative MDA-MB-231 cells, while a high pro-oxidant effect was found for the estrogen- dependent MCF-7 cells. A striking cell selectivity was obtained, with a more noticeable outcome on the triple-negative MDA-MB-231 cell line. Results: The main impact on the cellular biochemical profile was verified to be on proteins and lipids, thus justifying the compound´s anti-invasive effect and chemoprotective ability. Conclusion: p-Coumaric acid was thus shown to be a promising chemoprotective/chemotherapeutic agent, particularly against the low prognosis triple-negative human breast adenocarcinoma.


2021 ◽  
Vol 22 (9) ◽  
pp. 4961
Author(s):  
Maria Kovalska ◽  
Eva Baranovicova ◽  
Dagmar Kalenska ◽  
Anna Tomascova ◽  
Marian Adamkov ◽  
...  

L-methionine, an essential amino acid, plays a critical role in cell physiology. High intake and/or dysregulation in methionine (Met) metabolism results in accumulation of its intermediate(s) or breakdown products in plasma, including homocysteine (Hcy). High level of Hcy in plasma, hyperhomocysteinemia (hHcy), is considered to be an independent risk factor for cerebrovascular diseases, stroke and dementias. To evoke a mild hHcy in adult male Wistar rats we used an enriched Met diet at a dose of 2 g/kg of animal weight/day in duration of 4 weeks. The study contributes to the exploration of the impact of Met enriched diet inducing mild hHcy on nervous tissue by detecting the histo-morphological, metabolomic and behavioural alterations. We found an altered plasma metabolomic profile, modified spatial and learning memory acquisition as well as remarkable histo-morphological changes such as a decrease in neurons’ vitality, alterations in the morphology of neurons in the selective vulnerable hippocampal CA 1 area of animals treated with Met enriched diet. Results of these approaches suggest that the mild hHcy alters plasma metabolome and behavioural and histo-morphological patterns in rats, likely due to the potential Met induced changes in “methylation index” of hippocampal brain area, which eventually aggravates the noxious effect of high methionine intake.


2021 ◽  
pp. 096032712110134
Author(s):  
S Rahi ◽  
R Gupta ◽  
A Sharma ◽  
S Mehan

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disease characterized by cognitive and sensorimotor impairment. Numerous research findings have consistently shown that alteration of Smo-Shh (smoothened-sonic hedgehog) signaling during the developmental process plays a significant role in ASD and triggers neuronal changes by promoting neuroinflammation and apoptotic markers. Purmorphamine (PUR), a small purine-derived agonist of the Smo-Shh pathway, shows resistance to hippocampal neuronal cell oxidation and decreases neuronal cell death. The goal of this study was to investigate the neuroprotective potential of PUR in brain intoxication induced by intracerebroventricular-propionic acid (ICV-PPA) in rats, with a focus on its effect on Smo-Shh regulation in the brain of rats. In addition, we analyze the impact of PUR on myelin basic protein (MBP) and apoptotic markers such as Caspase-3, Bax (pro-apoptotic), and Bcl-2 (anti-apoptotic) in rat brain homogenates. Chronic ICV-PPA infusion was administered consecutively for 11 days to induce autism in rats. In order to investigate behavioral alterations, rats were tested for spatial learning in the Morris Water Maze (MWM), locomotive alterations using actophotometer, and beam crossing task, while Forced Swimming Test (FST) for depressive behavior. PUR treatment with 5 mg/kg and 10 mg/kg (i.p.) was administered from day 12 to 44. Besides cellular, molecular and neuroinflammatory analyses, neurotransmitter levels and oxidative markers have also been studied in brain homogenates. The results of this study have shown that PUR increases the level of Smo-Shh and restores the neurochemical levels, and potentially prevents morphological changes, including demyelination.


2012 ◽  
Vol 90 (9) ◽  
pp. 1149-1160 ◽  
Author(s):  
J.C. Winternitz ◽  
M.J. Yabsley ◽  
S.M. Altizer

Parasites can both influence and be affected by host population dynamics, and a growing number of case studies support a role for parasites in causing or amplifying host population cycles. In this study, we examined individual and population predictors of gastrointestinal parasitism on wild cyclic montane voles ( Microtus montanus (Peale, 1848)) to determine if evidence was consistent with theory implicating parasites in population cycles. We sampled three sites in central Colorado for the duration of a multiannual cycle and recorded the prevalence and intensity of directly transmitted Eimeria Schneider, 1875 and indirectly transmitted cestodes from a total of 267 voles. We found significant associations between host infection status, individual traits (sex, age, and reproductive status) and population variables (site, trapping period, and population density), including a positive association between host density and cestode prevalence, and a negative association between host density and Eimeria prevalence. Both cestode and Eimeria intensity correlated positively with host age, reproductive status, and population density, but neither parasite was associated with poorer host condition. Our findings suggest that parasites are common in this natural host, but determining their potential to influence montane vole cycles requires future experimental studies and long-term monitoring to determine the fitness consequences of infection and the impact of parasite removal on host dynamics.


2021 ◽  
Vol 11 (10) ◽  
pp. 1908-1917
Author(s):  
Rongkang Mai ◽  
Yiyao Cao ◽  
Huitian Yu ◽  
Yong Zheng ◽  
Juke Huang

80 male Wistar rats were stochastically assigned to Sham + Vehicle group, Sham + BUT group, PD + Vehicle group and PD + BUT group. Rotenone PD model rats were prepared by subcutaneous injection of rotenone sunflower oil emulsion 2 mg/(kg · d) for 5 consecutive weeks. Butylphthalide 80 mg/(kg · d) were given to the rats in Sham + BUT group and PD + BUT group by gavage from the first day of rotenone injection for 5 weeks. Subsequently, the motor retardation ability and the morphological changes of the substantia nigra (SN) of each group were evaluated. Meanwhile, the levels of neuronal injury, apoptosis, inflammation and oxidative stress in each group of rats were assayed. The impact of BUT treatment on miR-146a-5p expression and PI3K/AKT signal pathway in rat brain tissue was assayed. Finally, by constructing a PD cell model of the neurotoxin 6-hydroxydopamine (6-OHDA)-treated human neuroblastoma cell line SH-SY5Y, the in vitro anti-PD pharmacological effect of BUT was further verified.


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