Researchers from the University of Montpellier (France) have used cave paintings as a source of base line data to indicate whether there have been changes in the frequency of left– or right-handedness since ancient times. The clue lay in the 350 examples of “negative hands”, dating from 10,000 to 35,000 years ago, that are found in French and Spanish caves.
     Negative hands were created using a primitive airbrush technique whereby pigment was blown through a tube onto a dampened cave wall. One hand was placed against the wall and the other used to hold the tube. The blown pigment created an outline of the hand. The reasons for this practice are unclear, but the paintings do say something about handedness. It would be expected that the painter would use the dominant hand to hold the tube and leave the outline of the other hand on the wall. 77% of the cave paintings were of left hands, thereby showing probable right hand dominance. The researchers then had 179 students paint negative hands. The results were almost identical with the cave paintings. 77.1% were left hands.
     Handedness for blowing ink does not necessarily correlate with handedness for other functions, but the study does show a lack of variation for a particular task over many centuries. The results were reported in Biology Letters, published online by the Royal Society of Britain.

Source: New York Times (7 October 2003)