A herd of buffalo can move only 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 culling of the weakest members. In much the same way the human
brain can only operate as fast as the slowest brain cells. Excessive 
intake of alcohol, we all know, kills off 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, constantly making 
the brain a faster and more efficient machine.