There could, however, also be direct precopulatory female mate choice based on male genital traits. Before clothing, the nonretractable human penis would have been conspicuous to potential mates. This observation has generated suggestions that human penis size partly evolved because of female choice.
Here we show, based upon female assessment of digitally projected life-size, computer-generated images, that penis size interacts with body shape and height to determine male sexual attractiveness. Positive linear selection was detected for penis size, but the marginal increase in attractiveness eventually declined with greater penis size i. Penis size had a stronger effect on attractiveness in taller men than in shorter men. There was a Homo dudes are ready to take some mean penises increase in the positive effect of penis size on attractiveness with a more masculine body shape i.
Surprisingly, larger penis size and greater height had almost equivalent positive effects on male attractiveness.
Our results support the hypothesis that female mate choice could have driven the evolution of larger penises in humans. More broadly, our results show that precopulatory sexual selection can play a role in the evolution of genital traits. Male genitalia show great variation among closely related species 1. This variation is typically attributed to copulatory and postcopulatory sexual selection to increase male fertilization success under sperm competition 2 or cryptic female choice 3.
There might, however, also be premating sexual selection on male genitalia. Precopulatory processes can influence genital morphology 45but it is unknown whether these results are due to direct female choice or sexual conflict. In species where genitalia are externally visible, sexual selection might also act if females prefer males with specific genital morphology.
Despite this potential effect, relatively little research has tested whether primary sexual characters influence male attractiveness 6 — 8.
How female choice acts on any given male trait, and hence the strength and direction of selection, can be influenced by several, nonmutually exclusive factors. First, females use multiple cues during the mate choice process 9. Overall male attractiveness is unlikely to be determined by individual traits e. Second, traits within individuals are phenotypically and genetically correlated. These relationships can influence evolution via correlational selection Third, there might be a size contrast effect such that female assessment of attractiveness varies if the trait of interest is viewed differently in relation to other traits, analogous to the Ebbinghaus—Titchener effect For example, the same sized penis might be perceived differently on short and tall men.
Humans mate assortatively based on numerous traits, including height 15facial symmetry 16and body shape Homo dudes are ready to take some mean penises The upright body posture and protruding, nonretractable genitalia of male humans make the penis particularly conspicuous, even when flaccid. This observation has generated suggestions by evolutionary biologists that the comparatively large human penis evolved under premating sexual selection 19 Furthermore, novels, magazines, and popular articles often allude to the existence of a relationship between penis size and sexual attractiveness or masculinity 21 Many cultures have fashion items, like penis sheaths and codpieces, that draw attention toward male genitalia 20highlighting the potential for female choice to influence the evolution of male genitalia.
There are numerous psychological studies directly asking females for their preference regarding male penis size.
The results are mixed, with studies finding that females prefer longer penises 23wider penises 2425or that penis size is unimportant These studies, however, all use self-reported, direct questioning and are therefore susceptible to biases of self-censorship and pressure to conform to socially desirable responses to sensitive issues e.
The only scientific studies to attempt to test experimentally whether flaccid penis length affects male attractiveness asked women to rate five images created by modifying a single drawing of a male figure so that the test figures differed only in penis length 30 — These important studies were not designed to quantify directly the relative effect of penis length on attractiveness compared with other sexually selected male traits, such as height and body shape 30 — Therefore, it is still unknown whether penis size affects attractiveness when there is substantive variation in other, arguably more important, body traits, or whether interactions between these traits and penis size determine net attractiveness.
For example, does a given increase in penis length have an equivalent effect on the attractiveness of a short and tall man? In addition, the use of small photographs to quantify size-based preferences might lead to different estimates than those obtained when viewing fully life-sized male bodies. To address these issues, we presented a sample of heterosexual Australian women with projected life-size, computer-generated male figures Fig.
We tested for the Homo dudes are ready to take some mean penises of flaccid penis size, body shape shoulder-to-hip ratioand height on male sexual attractiveness. The latter two traits have regularly been investigated and are known to influence male attractiveness or reproductive success [height 1533 — 35shape 183637 ]. Homo dudes are ready to take some mean penises
This process eliminated any correlation between the three traits across the set of figures. Figure rating was conducted in the absence of an interviewer and was completely anonymous. There were highly significant positive linear effects of height, penis size, and shoulder-to-hip ratio on male attractiveness Table 1.
Linear selection was very strong on the shoulder-to-hip ratio, with weaker selection on height and penis size Table 1. There were diminishing returns to increased height, penis size, and shoulder-to-hip ratio quadratic selection: A model using only linear and quadratic selection on the shoulder-to-hip ratio accounted for The explanatory power of height and penis size when added separately to this model was almost identical.
Both traits significantly improved the fit of the model log-likelihood ratio tests: Each trait, respectively, explained an extra 6. Linear selection gradients and the matrix of quadratic and correlational selection gradients based on average rating for each of the figures and means of gradients generated separately for each participant.