Sex in Paarbindungen und die Bedeutung des Gesichts

Eine Frage, die ich mir neulich stellte, ist, welche Veränderungen durch die Paarbindung entstehen:

• Bei der Paarbindung wird die Anonymität des Sex aufgehoben (im Gegensatz zB zu einer Spermienkonkurrenz). Die Identität des Sexualpartners erhält damit eine besondere Bedeutung
• Vielleicht haben wir deswegen auch eine besondere Vorliebe für ein „hübsches Gesicht“ und auch dort im Wege der sexuellen Selektion viele besondere Attraktivitätsmerkmale angesammelt – bei Frauen etwa besonders volle Lippen (quasi vergleichbar mit den geschwollenen roten Hintern einer Affenarten), was dann eben heute dazu führt, dass sich Frauen die Lippen aufspritzen lassen und mit Lippenstift die Signalfarbe verstärken sowie den Mund optisch vergrößeren
• Weitere Attraktivitätsmerkmale im Gesicht sind große Augen, weswegen mit Schminke auch hier nachgeholfen wird, zudem hohe Wangenknochen als Zeichen für Erwachsenheit oder Signale wie leicht gerötete Wangen (Signalfarbe für Erregung) die auch mit Schminke nachgeamt wird.
• Auch beim Mann sind ein deutliches Kinn etc interessant.
• Das erklärt vielleicht auch, warum Sexualpraktiken wie die Missionar Stellung als besonders vertraut gelten, weil man sich dabei eben in die Augen und in das Gesicht schaut und so die Mimik und die Gefühle des Partners besser lesen kann. Andere Stellungen wie Doggy Style gelten dagegen als „wilder“ und insoweit sexueller und sind damit der Kurzzeitstrategie näher (in dem Sinne, dass sie eben die sexuellere Seite eher ansprechen als die Bindungsseite).
• Es könnte sich insoweit sexuelles Interesse auf das Gesicht verlagert haben, weil dieses aufgrund der Paarbindung zur Erforschung der Gefühle und genauer Beobachtung eh mehr beobachtet werden muss und daher das Prüfen der dortigen Fruchtbarkeitsmerkmale /Attraktivitätsmerkmale und das Entwickeln besonderer Attraktivitätsmerkmale im Wege der sexuellen Evolution leicht selektiert werden konnte

Das sexuelle Selektion ihre Spuren in unserem Gesicht hinterlassen hat, wird auch in dieser Studie vertreten:

We consider sex differences in human facial morphology in the context of developmental change. We show that at puberty, the height of the upper face, between the lip and the brow, develops differently in males and females, and that these differences are not explicable in terms of sex differences in body size. We find the same dimorphism in the faces of human ancestors. We propose that the relative shortening in men and lengthening in women of the anterior upper face at puberty is the mechanistic consequence of extreme maxillary rotation during ontogeny. A link between this developmental model and sexual dimorphism is made for the first time, and provides a new set of morphological criteria to sex human crania. This finding has important implications for the role of sexual selection in the evolution of anthropoid faces and for theories of human facial attractiveness.

Quelle: Biometric Evidence that Sexual Selection Has Shaped the Hominin Face

Aus der Studie:

Could the vertical modification of the anterior upper face in males and females be simply a by-product of developmental adjustments towards structural and functional balance? Or is there evidence to suggest that sexual selection, operating mainly through mate choice, has shaped the human face? Previously, ‘hormone markers’, singled out as cues that can affect judgements of male facial attractiveness [32], [33], have largely corresponded to regions of the face that grow allometrically, such as the lower jaw and browridges, and not necessarily to regions of the face that exhibit sex-specific size-independent variation, such as anterior upper facial height. A good example of a facial feature that is growth-related is cheekbone prominence: although male cheekbones are larger, female cheekbones appear more conspicuous than those of males, as the female nose, forehead and chin do not protrude to the same extent [5], [17]. Prominent cheekbones are attractive in both sexes but in females it is the relative anterior protrusion of the bone and amply overlying soft tissue [34] that defines them, as opposed to the degree of protrusion of the zygomatic bone laterally. In several studies of facial attractiveness [35]–[37] cheekbone prominence has been defined metrically by the ratio of the width of the face at the cheek-bones divided by the width of the face at the level of the mouth. The findings from these studies were not consistent as ‘cheekbone prominence’ in this context was found to be both greater in females [37]or greater in males [35], [36]. The sex-specific distinction (width-to-height of the upper face) reported here in a sample of modern humans, and potentially corresponding to facial dimorphism in other hominins, is quantifying different information, with width of the face across the cheekbones defined in relation to the height of the upper face and not defined in relation to the breadth of the lower jaw. The findings in this study suggest that, independent of any selection pressure on overall body size, it is upper facial height (and not facial breadth) that is the potential target of selection, as male upper faces are shorter than expected for their size. A divergence in the size of male and female traits usually occurs around male puberty at 12–14 years [4]. Our data confirm that sexual size dimorphism is present in most cranial traits (though to a variable degree) but is absent for FHT in post-pubescent individuals (Figure S3). The relationship between facial breadth across the cheekbones (BZW) and BCL (the usual proxy for skull size) is shown not to differ significantly between males and females, agreeing with predictions based on ontogenetic scaling, whereas the relationship between upper facial height and skull size (BCL) is shown to differ significantly between the sexes (Table 1, 2). This distinction, which separates facial variation hypothetically linked with sexual selective pressures acting on overall body size, from facial variation hypothetically linked with sexual selective pressures targeting a specific part of the face, is important as the latter should be able unambiguously to define adult male and female faces, whereas the former will fluctuate in accordance with variation in body size across human populations.