Researchers say rolling motion is rare in animals because it requires precisely coordinated movements

Researchers say rolling motion is rare in animals because it requires precisely coordinated movements

Social activities seem particularly effective at keeping mind sharp

Social activities seem particularly effective at keeping mind sharp

Artisans in third century BC created thousands of life-size terracotta figures to guard tomb of Emperor Qin Shihuang near Xi'an

Artisans in third century BC created thousands of life-size terracotta figures to guard tomb of Emperor Qin Shihuang near Xi'an