Everyone knows that a human hand has five fingers. They are long and short, thick and thin, and each finger has its own name: thumb, index finger, middle finger , ring finger and little finger.

A few days ago, I was sitting by the bed and cutting my nails. I discovered an interesting thing: there are two thicker lines on the index finger, middle finger, ring finger and little finger. The fingers are divided into three sections, but the thumb only has two sections. What is the significance of this structure?

I looked at my thumb carefully. As long as I bent it slightly, my thumb had two joints, while the other four fingers had three joints. I thought: Why do people have only two thumbs? I asked my mother this question. My mother thought about it for a long time and shook her head helplessly.

I looked up information on the Internet and found out that humans evolved from ancient apes. The ancient apes lived in the forest and crawled on all fours. When performing climbing activities, fingers or toes with three joints were very suitable, but thumbs (toes) with only two joints were not very useful. Later, the ancient apes learned to walk upright, and their upper limbs were liberated. Especially when they evolved into humans, because their hands were often used with tools, their thumbs became very thick and powerful. A group of well-developed thenar muscles are also produced in the human palm, allowing the thumb to cooperate with the other four fingers on the opposite side.

It is precisely this result that the thumb has the greatest effect. The idiom "second to none" means outstanding person, which refers to the thumb. This is indeed the case. According to statistics from scientists, almost all tasks involving fingers require the help of thumbs. The thumb can work independently or in conjunction with the other four fingers, such as writing, holding chopsticks, grabbing, etc.

I thought: Why does such an important thumb only have two sections? Scientists believe this structure is optimal for it. Because if the thumb consists of one section, it will be inconvenient for it to cooperate with the other four fingers to grasp objects; if the thumb has three sections, then it will appear weak and unable to succeed in some powerful movements.

I finally know the secret why the thumb has two joints.

Observe and think everywhere, and you will learn more!