Abstract Compelling evidence from many animal taxa indicates that male genitalia are often under postcopulatory sexual selection for characteristics that increase a male’s relative fertilization success. 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.e., quadratic selection). Penis size had a stronger effect on attractiveness in taller men than in shorter men. There was a similar increase in the positive effect of penis size on attractiveness with a more masculine body shape (i.e., greater shoulder-to-hip ratio). 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.
从许多动物类群得到的令人信服的证据表明：男性生殖器通常在性行为后被选择由于其提高男性相对受精成功率的特性。 然而，女性也可能在性交前直接根据男性生殖器特征来选择配偶。人类在有着装之前，男性突起的阴茎对他们潜在的配偶来说是非常惹人注目的。 这一发现说明人类阴茎尺寸的演变的一部分原因是女性的选择。这里我们说明了，根据女性对数字投影真人大小，计算机生成图像的评估， 阴茎尺寸配合体型和身高决定了男性的性吸引力。 对阴茎尺寸的选择是正线性的， 但是吸引力的轻微上升最终因为更大的阴茎尺寸下降了（例如二次选择）。阴茎尺寸对高个男的吸引力影响比对矮个男的吸引力影响要强。阴茎尺寸对拥有更男性化的体型的男性的吸引力具有相似的正影响的提高。 神奇的是，更大的阴茎尺寸和更高的身高几乎对男性吸引力具有相同的正影响。 我们的结论支持女性配偶选择能促进人类演化出更大的阴茎这个假设。 更广义地说，我们地结论说明了交配后性选择对生殖器特征的演变具有影响。