Human penis size may indicate male attractiveness and fighting ability, with a larger size more attractive to women and more likely to intimidate rivals, according to Australian and South African researchers. The team asked more than 600 male and 200 female participants to rate computer-generated male figures that varied in height, body shape, and penis size. Women rated the figures’ sexual attractiveness, while men assessed how threatening they found them, both in terms of fighting ability and as a sexual rival. Women rated taller male figures with a higher shoulder-to-hip ratio (indicating a more V-shaped body) and a larger penis as being more attractive, but only up to a point, when further increases in penis size made little difference. Males also rated taller figures with more V-shaped bodies and larger penises as being more intimidating, both as sexual rivals and fighting opponents. But, in contrast to females, men consistently ranked males with ever larger penises as more of a sexual threat, suggesting they overestimate the importance of penis size in attracting a mate. These pressures may help explain why humans evolved larger penises than other primates, the authors conclude.