Kerri Johnson/UCLA

ScienceShot: Man or Woman? The Shadow ... Doesn't Know

A waist that arcs in like an hourglass, hips that jut out underneath: It's the classic figure of a woman. But does the curviness of the real average woman (above, left) and average male (above, right) match up with the images in people's minds? Not according to a new study, which finds that people frequently misjudge female silhouettes as male, while they rarely make the reverse mistake. Scientists analyzed measurements of almost 5000 Army recruits and determined that the boundary between the two sexes' body shapes falls at a waist-to-hip ratio (WHR) of 0.8049: Most males have a higher WHR and most women a lower WHR. But when 53 undergraduate students were asked to characterize a range of silhouettes, their guesses changed from female to male at a WHR of 0.68, lower than both the average female's WHR (0.71), and the lowest WHR seen among any male Army recruits (0.74). The average WHR that the students guessed as female was so extreme that it was never seen among real women, the team reports online today in the Proceedings of the Royal Society B. The effect may be a consequence of a "better safe than sorry" approach to protect humans throughout evolution from misjudging faraway males, who historically were more likely to take aggressive action than females.

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