Fear is a response to defend against dangers.
The fifth basic emotion is fear.
Fear is an emotion which branches out from interest depending on the situation. All fearful things are interesting. For example, herbivorous animals keep a reasonable distance from lions and cheetahs. Also chimpanzees or baboons sometimes surround a big python when they find it.
Humans may feel fear when standing somewhere heigh or unstable, crossing a rope bridge, they are in front of a violent animal or a truck being driven recklessly, or seeing a snake like wiggling thing.
It is thought that we feel fear when we can imagine the current situation causing pain. Therefore, horror stories are told like the object of horror is present at the time. Fear occurs when we must react immediately to the current situation.
Fearful things don't have features in common with each other, therefore they evolved individually through natural selection. That is to say that there is not only one gene for fear.
Children who are raised in a high-rise apartment building are sometimes not afraid of heights. This is because fear needs to be learned. Like with other emotions, only the foundation is hereditary.
Fear has a special facial expression. For example, The eyebrows are raised, wrinkles are formed in the center of forehead, eyes are opened very wide, eyelids are pulled up, the white of the eye is increased, mouth is opened little and pulled backward. This expression has been confirmed to weaken an attack when the object of fear is a human.
Actions of fear include crying or running away depending on the situation. If it's possible we will run away, if it's not possible we will cry and scream, and crouch down. We flee, call for help, defend ourselves, and panic when we feel fear.
Thanks to these actions of fear, we can avoid danger and survive.