Tonsils are not useless lumps sitting at the back of the throat.
They are part of the immune system.
Their location puts them close to one of the major entry points into the body.
Tonsils are lymphatic tissue
The tonsils contain immune cells.
They sit where air, food, saliva, and countless microbes pass through the mouth and nose.
That gives the immune system a chance to sample material entering the body.
Why are tonsils especially important in childhood?
The immune system is still learning about the environment during childhood.
Tonsils can be especially active during those years.
They participate in recognizing microbes and helping organize immune responses.
Why do tonsils get infected?
Their location exposes them to viruses and bacteria constantly.
That makes them useful immune tissue, but it also means they can become inflamed or infected.
Tonsillitis simply refers to inflammation of the tonsils.
Why are tonsils sometimes removed?
Some people develop repeated serious tonsil infections.
Others have tonsils large enough to interfere with breathing or sleep.
In those situations, removal may be recommended.
Can you live without tonsils?
Yes.
The immune system contains lymphatic tissue throughout the body.
Removing the tonsils does not remove your immune system.
It simply removes one part of a much larger network.
Are tonsils evolutionary leftovers?
No.
They have a real immune function.
That does not mean everyone needs to keep them no matter what.
A body part can be useful and still become enough of a problem that removing it makes sense.
So tonsils are not useless leftovers.
They are one security checkpoint in a very large airport.
The same body systems connect with Why do we have an appendix?, another everyday effect with its own underlying mechanism.
And that’s the short explanation.
Related explanations: Why do we have an appendix?, Why do we cough?, and Why does your nose get stuffy?