Evolution (again)
1st year Biology. The lecturer is explaining the idea of spandrels: how not every evolved trait is necessarily an advantage but may be a trait caused by another trait which is an advantage. The classic examples being male nipples (there is no evolutionary benefit in males having nipples but also no evolutionary cost, but there is a strong benefit in females having milk producing organs, and since both are caused by the same underlying genes, the benefit bestowed on females wins out), and the chin (having a chin is a function of having a jaw, which is a distinct advantage).

All this was lost on one poor lass who came out and told a non-bio friend that humans will soon evolve to have no chin as it served no purpose.
( Sextant goes to him is emotionally erect, on this day, Sun 21 Mar 2010, 2:34, Reply)