BuffaloTheory of Beer 
The answer to one of life's great mysteries! I haven't heard anyone
explain this as well as the all wise Cliff Clavin, on the sitcom Cheers. One
afternoon at Cheers, Cliff Clavin was explaining the Buffalo Theory
to his buddy Norm... 
"Well ya see Norm, it's like this... A herd of buffalo can only move
as fast as the slowest buffalo. And when the herd is hunted, it is the
slowest and weakest ones at the back that are killed first. This natural
selection is good for the herd as a whole, because the general speed and health
of the whole group keeps improving by the regular killing of the weakest
members." 
He continues: "In much the same way, the human brain can only operate
as fast as the slowest brain cells. Excessive intake of alcohol, as we
all know, kills brain cells, but naturally it attacks the slowest and
weakest brain cells first. In this way, regular consumption of beer
eliminates the weaker brain cells, making the brain a faster and more efficient
machine.  That's why you always feel smarter after a few beers."