Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.

Anthropologists have pieced together the little they know about the history of left - handedness and right - handedness from indirect evidence. Though early men and women did not leave written records, they did leave tools, bones, and pictures. Stone Age hand axes and hatchets were made from stones that were carefully chipped away to form sharp cutting edges. In some, the pattern of chipping shows that these tools and weapons were made by right handed people, designed to fit comfortably into a right hand. Other Stone

Age implements were made by or for left-handers Prehistoric pictures, painted on the walls of caves, provide further clues to the handedness of ancient people. A right - hander finds it easier to draw faces of people and animals facing toward the left, whereas a left - hander finds it easier to draw faces facing toward the right. Both kinds of faces have been found in ancient painting. On the whole, the evidence seems to indicate that prehistoric people were either ambidextrous or about equally likely to be left - or right - handed.

But, in the Bronze Age, the picture changed. The tools and weapons found from that period are mostly made for right - handed use. The predominance of right - handedness among humans today had apparently already been established.

What is the main topic of the passage?