I’m not sure what’s more amusing, that people are studying how penis size affects male attractiveness or that the authors of the study are all men. Brian Mautz and Michael Jennions of Australian National University, Bob Wong from Monash University and Richard Peters of La Trobe University addressed the question of whether sexual selection could have played a role in the evolution of male genitalia. See, this is a serious study.
The authors presented 105 heterosexual women with life-sized computer-generated images of naked men. While there are obviously men who could also weigh in on penis preference, those relationships are irrelevant from an evolutionary standpoint. Enough said about that. The images varied in three ways: height, body shape and flaccid penis size, each with seven possible dimensions; thus, there were a total of 343 different images (there are examples in the paper, which I’m not going to reproduce here). The women were each shown a random subset of 53 of the images and asked to rank them for ‘attractiveness as sexual partners’.
The most important trait of the three being tested was body shape. Specifically, women liked to see the right shoulder to hip ratio in their potential paramours. In fact, nearly 80% of the variation in attractiveness could be accounted for by this one characteristic. Height and penis size did add a bit to the equation, but only about 6% and 5% respectively. Not surprisingly, taller women considered height to be more important than shorter women did.
UPDATE 4/10/13: Greg Laden has some interesting points about why the whole premise of paleolithic women being able to evaluate and select mates based on penis size is flawed at his blog.
Mautz, B., Wong, B., Peters, R., & Jennions, M. (2013). Penis size interacts with body shape and height to influence male attractiveness Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1219361110.