Like two nostrils

How many nostrils does a person have?

Two? Four? Six?

It's four o'clock. Two you can see, two you can't see.

This discovery comes from the observation of fish breathing. Fish get oxygen from water. Most of them have two pairs of nostrils, one forward and the other backward. The question is, if humans evolved from fish, where is the other pair of nostrils?

The answer is: the human nostril has degenerated to the inside of the head, which is called "posterior nostril" and Greek is called "funnel". This pair of nostrils is connected with the throat, so that we can breathe through the nose.

In order to do this, the pair of "posterior nostrils" must move backwards through the teeth. It sounds incredible, but recently, scientists in China and Sweden found that this respiratory function of "primitive fleshfin fish" (fish from China 395 million years ago) has evolved by half. This fish has two holes between its front teeth, which are similar to nostrils.

This fish is the primitive ancestor of land animals. It can breathe in the air or in the water. Its pair of rear nostrils can make it perch in shallow water for food, while the other pair of nostrils emerge from the water like crocodiles.

Similar gaps can be seen in the middle of the early teeth of human fetuses. If the gaps are not connected, it becomes a cleft palate. It seems that an ancient fish fossil explains the mystery.

By the way, the latest research on nostrils shows that we can use two external nostrils to detect different smells and create a three-dimensional nasal sound according to the amount of air inhaled.