The facial width-to-height ratio (FWHR) is the width of the face divided by the height of the upper face. There is mixed evidence for the hypothesis that the FWHR is a cue of threat and dominance in the human face. We conducted a systematic review and meta-analyses of all peer-reviewed studies (and 2 unpublished studies) to estimate the magnitude of the sex difference in the FWHR, and the magnitude of the relationship between the FWHR and threatening and dominant behaviours and perceptions. Studies were eligible for inclusion if the authors reported an analysis involving the FWHR. Our analyses revealed that the FWHR was larger in men than in women ( = .11, n = 10,853), cued judgements of masculinity in men ( = .35, n of faces = 487; n of observers = 339), and was related to body mass index ( = .31, n = 2,506). Further, the FWHR predicted both threat behaviour in men ( = .16, n = 4,603) and dominance behaviour in both sexes ( = .12, n = 948) across a variety of indices. Individuals with larger FWHRs were judged by observers as more threatening ( = .46, n of faces = 1,691; n of observers = 2,076) and more dominant ( = .20, n of faces = 603; n of observers = 236) than those with smaller FWHRs. Individuals with larger FWHRs were also judged as less attractive ( = -.26, n of faces = 721; n of observers = 335), especially when women made the judgements. These findings provide some support for the hypothesis that the FWHR is part of an evolved cueing system of intra-sexual threat and dominance in men. A limitation of the meta-analyses on perceptions of threat and dominance were the low number of stimuli involving female and older adult faces.

The beard is a strikingly sexually dimorphic androgen-dependent secondary sexual trait in humans. Darwin posited that beards evolved in human ancestors via female choice as a highly attractive masculine adornment. Others have since proposed that beards evolved as a signal of male status and dominance. Here, we show that women from two very different ethnic groups, Europeans from New Zealand and Polynesians from Samoa, do not rate bearded male faces as more attractive than clean-shaven faces. Women and men from both cultures judge bearded faces to be older and ascribe them higher social status than the same men when clean-shaven. Images of bearded men displaying an aggressive facial expression were also rated as significantly more aggressive than the same men when clean-shaven. Thus, the beard appears to augment the effectiveness of human aggressive facial displays. These results are consistent with the hypothesis that the human beard evolved primarily via intrasexual selection between males and as part of complex facial communication signaling status and aggressiveness.