"Human beings are rational animals."
That one made me chuckle.
![laugh laugh](/images/graemlins/default/laugh.gif)
Just do a search on youtube for something like "redneck fails" or look at how people spend their time or money. Kind of brings that statement into serious question.
Maybe something along the lines of "Human beings have the capability of sometimes (or maybe occasionally) being rational animals" would be a more correct statement.