In every culture and every ethnicity around the world people blush but animals don't. It's not just the most animal's faces are covered in fur, feathers and stuff so we can't see them blushing—they actually don't blush.
Charles Darwin called "blushing" as the most peculiar and most human of all expressions.
Which is awesome, however, why do we blush easy? Logically, we understand it, like we get the mechanic when you’re embarrassed because of slipping on the dirt that many people saw you or you are in the front of our crush.
Well, our face turns red because our “Sympathetic Nervous System” kicks in. That's the network of nerves that controls your 'fight or flight' response.
When it's triggered it signals the release of adrenaline, suddenly your heart rate picks up, start breathing faster and then you're ready to runaway. Your pupils dilate and blood rushes to your brain, you can take in as much information as possible and your blood vessels dilate in a process called vasodilation to improve oxygen flow. It's basically the same effect you get from warming up before a workout.
But, in the very hypothetical instance of when you slipped into dirt, the blood vessels in your face responding specifically to a chemical transmitter called a Adenylyl Cyclase. It basically tells the blood vessels in your face to let the adrenaline in. The weird thing is that the superficial blood vessels in your face aren't usually affected by sympathetic responses. This explains why we don't blush when we're scared. If we did, that might be a sign that blushing served some sort of survival purpose.
However, it only happens when we're not actually in danger. So, why?
Well, some scientists believe the blushing evolved as a social survival trait.
When you blush than the person who's angry. You can see that you're really sorry
If the person who's laughing, you can see that you're visibly embarrassed.
We may never know for sure why blushing became a thing. But it could just be our way of saying, sorry for making you blue.