听力材料：
Human culture could not have developed without the human hand. Chimpanzees and gorillas walk on their hands, and orangutans use their hands primarily for holding branches, but the human hand is both tool and toolmaker, as well as an extension of the brain. Next to the brain, the hand is probably our greatest possession. Other animals may run faster than us, or have better senses, but no other animal comes close to matching our manual skills.
The power of the human hand comes from the way the brain controls it. The brain coordinates the hand’s actions with signals from the eyes, directing the hand by feeding it complex instructions at an almost automatic level. The human hand is capable of both brute strength and delicate tasks. The hand can perform hard physical labor, yet it’s also sensitive to slight changes in form and texture—so much so, in fact, that the hand is a substitute eye to people who are blind.
A key aspect of our manual skill is the ability to use our fingers independently rather than having to use them all together. The human hand has two characteristics that make us different from any other animal: the opposable thumb and the double grip. The first of these, the opposable thumb, has the ability to oppose—to face—the other fingers, so it can touch every part of every other finger on the same hand. The second characteristic is the double grip. This means that one hand can hold two billiard balls separately, for example. We can grip one ball between our last two fingers and our palm, and hold the second ball between our forefinger and thumb. Having strength and delicacy combined like this makes the human hand more skilled than any limb on any other animal. The opposable thumb and the double grip put us in the top class for tool making and for doing whatever else our brain tells our hands to do.
Question：
Using points and examples from the lecture, explain why the human hand is a valuable possession.
