Why Did We Ever Start This Tradition Of Clinking Our Glasses Together Before Drinking?

I've always been interested in humanities little traditions. The things that we've all been doing for so long that nobody stops to think why we started doing them to begin with. Cheers and clinking glasses is the perfect example of that. It is crazy to me that it started simply with self preservation. People were dying so often by poison in a glass that they had to start mixing their glasses by smashing them together. Who knows how many deaths were caused by swapping germs from this tradition, but definitely resulted in fewer intentional poisonings and...just a fun thing to do at dinner. Cheers to you guys, I love you.