NARRATOR：

Now listen to part of a lecture on the topic you just read about.

FEMALE PROFESSOR：

None of the three theories presented in the reading passage are very convincing.

First, the stone balls as hunting weapons.

Common Neolithic weapons such as arrowheads and hand axes generally show signs of wear.

So we should expect that if the stone balls had been used as weapons for hunting or fighting, they too would show signs of that use.

Many of the stone balls would be cracked or have pieces broken off.

However, the surfaces of the balls are generally very well preserved, showing little or no wear or damage.

Second, the carved stone balls may be remarkably uniform in size, but their masses vary too considerably to have been used as uniform weights.

This is because the stone balls were made of different types of stone, including sandstone, greenstone, and quartzite.

Each type of stone has a different density. Some types of stone are heavier than others.

Just as a handful of feathers weighs less than a handful of rocks, two balls of the same size are different weights depending on the type of stone they’re made of.

Therefore, the balls could not have been used as a primitive weighing system.

Third, it’s unlikely that the main purpose of the balls was as some kind of social marker.

A couple of facts are inconsistent with this theory.

For one thing, while some of the balls are carved with intricate patterns, many others have markings that are extremely simple—too simple to make the balls look like status symbols.

Furthermore, we know that in Neolithic Britain, when someone died, particularly a high-ranking person, they were usually buried with their possessions.

However, none of the carved stone balls have been actually found in tombs or graves.

That makes it unlikely that the balls were personal possessions that marked a person’s status within the community.