 The first dildos were made of stone, tar, wood, bone, ivory, limestone, teeth, and other materials that could be shaped as penises and that were firm enough to be used as penetrative sex toys.Scientists believe that a 20-centimeter siltstone phallus from the Upper Palaeolithic period 30,000 years ago, found in Hohle Fels Cave near Ulm, Germany, may have been used as a dildo.Prehistoric double-headed dildos have been found which date anywhere from 13–19,000 years ago.