For about as long as humans have created works of art, they've also left behind handprints. People began stenciling, painting, or chipping imprints of their hands onto rock walls at least 30,000 years ago.

Until recently, most scientists assumed these prehistoric handprints were male. But "even a superficial examination of published photos suggested to me that there were lots of female hands there," Pennsylvania State University archaeologist Dean Snow said of European cave art.

By measuring and analyzing the Pech Merle hand stencils, Snow found that many were indeed female--including those pictured here.