Men beware: Your voice could give away how often you hit the gym. Researchers recorded men from different backgrounds—the Tsimane Indians of Bolivia, Andean farmers in Argentina, and both U.S. and Romanian college students—speaking a short phrase such as "This is an experiment, over and out," in their native language; they also measured the circumference of each man's flexed bicep. Using a seven-point scale, American men and women could accurately estimate each man's relative strength when listening to the recordings, the team reports  online tomorrow in the Proceedings of the Royal Society B. The researchers didn't determine exactly what vocal quality gives the guys away, but since the effect holds across cultures, it probably evolved long ago. The researchers think the capacity allowed our ancient ancestors to assess a sparring partner's fighting ability when visual cues were insufficient, such as when light was dim or a rival was far away.
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