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.
In much the same way, the human brain can only operate as fast as the
lowest 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 elimates the weaker brain
cells, making the brain a faster and more efficient machine. That's
why you always feel smarter after a few beers.