Evidence of Predominant Right-Handedness in Early Humans

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Archaeological records paintings, drawings, and carvings of humans engaged in activities involving the use of hands indicate that humans have been predominantly right-handed for more than 5,000 years. In ancient Egyptian artwork, for example, the

Line right-hand is depicted as the dominant one in about 90percent of the examples. Fracture 5 or wear patterns on tools also indicate that a majority of ancient people were right-handed. Cro-Magnon cave paintings some 27,000years old commonly show outlines of human hands made by placing one hand against the cave wall and applying paint with the other. Children today make similar outlines of their hands with crayons on paper. With few exceptions, left hands of Cro-Magnons are displayed on cave walls, indicating that 10 the paintings were usually done by right-handers.

Anthropological evidence pushes the record of handedness in early human ancestors back to at least 1.4 million years ago. One important line of evidence comes from flaking patterns of stone cores used in tool making: implements flaked with a clockwise motion indicating a right-handed toolmaker can be distinguished from 15 those flaked with a counter-clockwise rotation indicating a left-handed toolmaker.

Even scratches found on fossil human teeth offer clues. Ancient humans are thought to have cut meat into strips by holding it between their teeth and slicing it with stone knives, as do the present-day Inuit. Occasionally the knives slip and leave scratches on the users' teeth. Scratches made with a left-to-right stroke direction by right-handers 20 are more common than scratches in the opposite direction made by left- handers.

Still other evidence comes from cranial morphology: scientists think that physical differences between the right and left sides of the interior of the skull indicate subtle physical differences between the two sides of the brain. The variation between the hemispheres corresponds to which side of the body is used to perform specific 25 activities. Such studies, as well as studies of tool use, indicate that right- or left-sided dominance is not exclusive to modern Homo sapiens. Populations of Neanderthals, such as Homo erectus and Homo habilis, seem to have been predominantly right-handed, as we are.