Over time, the shapes of the bones as well as the increase of terminal nerve endings used for sensing pressure have equipped the hand of the Homo species with high levels of sensitivity and dexterity which were completely new characteristics in the evolution of primates and hominids. The hand has allowed humans to work stones into tools as well as to create images and symbols which have permanently imprinted in their habitat. Thinking and memory were further developed thanks to the ability to manipulate objects and transmit ideas on materials external to the human body by making instruments and simple drawings. In Paleolithic art, the hand is one of the most often portrayed objects. Positive or negative handprints can be found all over the world (from the Cueva de las Manos in Argentina to Altamira caves in Spain) and date back to a wide-ranging period (c. 40.000-7.000 BC).