In addition, they all painted positive and negative hands. To make them positive, they taped their hands with pigments and placed them on the wall; then, to fill imperfections and gaps, they were given the final touches. For the negative hands, they would pick up the pigments in their mouth, put their hand on the wall and blow directly or with cane tubes. Thus, the silhouette of the hand was marked on the wall.

The experts are clear on what technique they used and that the hands are related to the creation of abstract thought, with a symbolic meaning. But what did they mean? Why did they paint? These questions have raised many hypotheses, but they have received few answers.

The archaeologist Dean Snow at the University of Pennsylvania believes these hands were female and that when men were going to hunt, women painted them as rituals for hunting to be fruitful. But this theory has an obvious gap: we recently learned that women were also hunting. Other experts say that if the hands are really women's, you can't prove it either, maybe because community training was at your fingertips, they had a didactic function.

Another characteristic of the hands is that many hands lack some fingers or phalanx. In 1922, archaeologist G. H. Luquet stated that they did not represent real mutilations, since no skeletons have been found with this type of mutilation. In the 1960s, well-known historian A. Leroi-Gourhan adhered to this hypothesis and suggested that “mutilated” hands could be the expression of a sign language. There are also those who believe that they used these hands to count and that, therefore, mutilated hands are numbers. But a study published in 2018 in the Journal of Paleolithic Archeology states that finger mutilation was a common practice of sacrifice and that no other meaning should be sought.

In these hands around the world, most of them are left hands. In the Pyrenean cave of Gargas, for example, 124 of the 150 perfectly separable hands are from the left. For some, the right hand would symbolize work and the left would symbolize spirituality. But there's another more practical explanation: if you paint with your right hand, the logical thing is to use the model on the left.

Ángel Rivera and Mario Menéndez, professor at UNED, give hands at least a general meaning: one part represents the whole and, therefore, the hand would represent the whole human body. The painter would leave the mark of his being through his hand, a kind of signature.

In 2016, the European Union launched the HandPas project to unravel the mystery of hands and an international and interdisciplinary team has been investigating different issues. Are hands just the work of Cromagnon or that artistic expression that they created in contact with Neandertal? Did they use their hands to relate to the spirits? Dario Seglie, director of the Museum of Prehistoric Art of Pinerolo (Turin, Italy), states that we cannot expect an answer: “Those hands of the past are mute, we cannot make them speak”.

And yet, today, in many parts of the world, when children begin to express themselves with plastic art, stain their paint hands and mark them on a surface, or do negative hands, for example, drawing silhouette with pencil. That is, 40,000 years later, hands remain one of the most basic artistic manifestations of human beings.