Eine interessante Studie untersucht die Schönheitsideale „Große Brüste und schmale Taille“:
Physical characteristics, such as breast size and waist-to-hip ratio (WHR), function as important features used by human males to assess female attractiveness. Males supposedly pay attention to these features because they serve as cues to fecundity and health. Here, we document that women with higher breastto- underbreast ratio (large breasts) and women with relatively low WHR (narrow waists) have higher fecundity as assessed by precise measurements of daily levels of 17-β-oestradiol (E2) and progesterone. Furthermore, women who are characterized by both narrow waists and large breasts have 26% higher mean E2 and 37% higher mean mid-cycle E2 levels than women from three groups with other combinations of body-shape variables, i.e. low WHR with small breasts and high WHR with either large or small breasts. Such gains in hormone levels among the preferred mates may lead to a substantial rise in the probability of conception, thus providing a significant fitness benefit.
Quelle: Large breasts and narrow waists indicate high reproductive potential in women (PDF)
Ich würde vermuten, dass es eine gegenseitige Beeinflussung war:
Die Entwicklung hin zu schmalen Hüften könnte so abgelaufen sein. Mit dem sich immer mehr vergrößernden Gehirn mussten die Frauen auch immer breitere Becken bekommen, damit sie die Kinder gebären konnten. Demnach war es für Männer interessant auf Frauen mit breitem Becken zu stehen. Also hat sich dieses Merkmal im Wege der sexuellen Selektion verfestigt. Allerdings wurde es damit gleichzeitig für die Frauen ein Vorteil im Rahmen der sexuellen Selektion breite Becken zu haben. Allerdings kann man das Becken nicht beliebig verbreitern, weil dies wiederum Schwierigkeiten beim Laufen etc mit sich bringen würde. Also blieb nur der Weg, die Taillen enger werden zu lassen, damit das Becken breiter wirkt. Da das Merkmal bereits im Wege der sexuellen Selektion festgeschrieben war, brachte es damit auch für Männer etwas diesen Trick mitzumachen, da sie dann eine Chance auf Töchter mit breiten Becken, aber schmalen Taillen hatte, die dann wieder attraktiver für Männer war. Das ist das bizarre an sexueller Selektion: Bis zu einem bestimmten Grad benötigt sie keinen Sinn. Da die Steuerung dabei über Hormone erfolgte liegt es nahe, die beste Kombination von Hüfte und Taille bei dem höchsten Fruchtbarkeitsstand zu erreichen. Deswegen waren diese Merkmale auch gleichzeitig wieder ein Zeichen für Fruchtbarkeit, was die sexuelle Selektion gleich noch einmal verstärkt.
Bei Brüsten ist eine Theorie, dass sie ein Fitness Indicator sind, ein costly signal für Jugend. Geoffrey Miller erklärt das in „The Mating Mind“ (S. 245):
Breasts also make good fitness indicators because they come in symmetric pairs. I mentioned earlier that many bodily ornaments in many species advertise an aspect of fitness called developmental stability When body traits grow in pairs, perfectly symmetric development of the pair indicates high fitness. The paired traits tend to grow large to make their symmetry more obvious during mate choice. Evolutionary psychologists John Manning and Randy Thornhill have shown that women with more symmetric breasts tend to be more fertile. It is possible that bipedalism made breasts a useful potential cue of developmental stability for male mate choice. Once men started paying attention to the symmetry of breast development, high-fitness women could better display the symmetry by evolving large breasts. The larger the breasts, the easier it is to notice asymmetries. Perhaps single mastectomies are so distressing to women because breast symmetry has been such an important fitness cue during human evolution. Large human breasts may have evolved to advertise fitness through their symmetry, not just youth through their pertness.
Finally, breasts are pretty good indicators of fat reserves. In the Pleistocene, starving was more of a problem than overeating. It was harder to have good fat reserves than to be extremely thin, because women had to use their own energy and intelligence to gather food from their environment. It would be possible to spread one’s fat evenly over the whole body surface, like a porpoise, but that would make it hard for men to compare females, and it would give females too much insulation under the scorching African sun. Females who concentrated their fatdisplays in breast and buttocks could attract male interest without overheating. Also, by not depositing too much fat on the abdomen (as males tend to), females could avoid appearing pregnant already—a sure sign of not being fertile at the moment, which might inhibit male sexual attention. Breasts appear to have evolved as highly condition-dependent indicators of a woman’s nutritional state. Most women who have tried dieting know that breast size is the first thing to shrink when food intake is restricted. The role of breasts as fitness indicators may help to explain why there is so much variation in breast size among women. If large breasts were critical for breast-feeding, which is one of the single most important stages in mammalian reproduction, all women would have large breasts. But as we have seen, fitness indicators do not tend to converge on a single size in a population. They maintain their variation indefinitely, due to the effects of genetic mutation and variation in condition. It has sometimes been argued that men’s preferences for larger-than-average breasts must be an artifact of modern culture, because, if it were ancient, all women would have already have evolved large breasts. This argument is wrong if breasts evolved as fitness indicators. Bra manufacturers offer a range from A-cups to D-cups because evolution amplifies the variation in each fitness indicator rather than using it up.
Es spricht demnach vieles für eine biologische Begründung des Schönheitsideals. Diese Faktoren erscheinen mir wesentlich plausibler als eine reine Begründung über die Kultur, weil sie erklären können, warum Körper auf eine gewisse Weise entstanden sind und warum wir bestimmte Merkmale erregend finden. Die Queertheore muss zum einen die Frage, warum weibliche Menschen Brüste haben ausklammern und zum anderen sexuelle Selektion, die vererbbare Attraktivitätsmerkmale erfordert ausblenden. Es ist wenig plausibel, dass Menschen mit ihrem sehr entwickelten Gehirn nicht auch auf Fruchtbarkeitszeichen geachtet haben und die Vorteile sexueller Selektion genutzt haben.
Alles Evolution 