The Crucial Difference Between a Cupcake and a Muffin

Is frosting? I was not sure, and this questions has nagged at my very soul for quite some time. This Friday, when I made cupcakes for the office, the question resurfaced. Alan swears that the only difference is frosting, but I am not convinced. After all, cannot a muffin be more healthy for you because it can contain wheat and bran? A cupcake by nature would never be as healthy for you.
Isn't a cupcake a little cake? Where as a muffin was not originally created to be a little muff-cake? Aren't muffins more related to bread?
I was talking about this with my new Admin person at work, and it occurred to me that maybe muffins are originally from Brittan. After all, I am positive that English Muffins existed before the (American?) Muffin did. Maybe the present day version of the muffin is a knock off of the English Muffin, made bigger and better by adding more fat.
I turned to Wikipedia for an answer. Unfortunately this website was not extremely insightful. It did not mention that Muffins originally came from England, which kind-of discards my hypothesis. However it did mention that in recent decades muffins have become almost indistinguishable from cupcakes because the fat and sugar proportions have increased dramatically. The true origin of muffins is lost, but it is believed to be related to cornbread and breakfast. Cupcakes were invented in the 1800s. They started out as mini, individual, cakes that measured a cup.