Stone Balls Be Used As A Weapon

The passage mainly discusses the purpose of stone balls that were being used in the ancient times. However, the lecturer cast doubts on the writer’s view by using several points.
First of all, it is said in the passage that the stone balls were being used as a weapon. However, the listening argues that there has no cracks and breaking pieces on the stone balls. If the stone balls was used as a weapon, there must be some cracks on the balls while they throw them to the targets, but it turns out that these balls were well preserved. So the information that the reading provides is not convincing enough. This where the speaker disagrees with the writer.
Second, the writher proposed that the stone balls could be used as a kind measurements because