Human' s Hands
Archaeological records--paintings, drawings, and drawings 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 fight-hand is depicted us the dominant one in about 90 per- cent of the examples. Fracture or wear patterns on tools also indicate that a majority of ancient people were fight - handed.
Cro - Magnon cave paintings some 27,000 years 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. out- lines of their hands with crayons on paper. With few exceptions, left hands of Cro-Manganese are displayed on cave wails, indicating that the paintings were usually done by right-handers.
Anthropological evidence pushes the record of' handedness nearly 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 toolmaking: implements flaked with a clockwise motion (indicating a right -handed toolmaker) can be distinguished from 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) are more common than scratches in the opposite direction (made by lefthanders).
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 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 erects and Homo habilis, seem to have been predominantly right -handed, as we are.
What is the main idea of the passage？

A. Human ancestors became predominantly right- handed when they began to use tools.
B. It is difficult to interpret the significance of anthropological evidence concerning tool use.
C. Human and their ancestors have been predominantly right - handed for over a million years.
D. Human ancestors were more skilled at using both hands than modern humans.