Answer by Neville Fogarty:
It appears that the granddaddy of cakes is a product of the Ancient Egyptians: http://www.syl.com/travel/thehistoryofbakedgoodsincludestheinventionofcake.html
The invention of cake originated in ancient Egypt as round, flat, unleavened breads that were cooked on a hot stone. The evolution of baked goods continued over many centuries through the introduction of new ingredients and the invention of new techniques of baking. The Egyptian's discovery and skill at using natural yeast helped those flat breads to leaven.
The difference between a bread and a cake was almost undistinguishable. The main difference was in their shape and that cakes were a little bit sweeter. But with the passage of time that difference has become more evident – bread is a staple food and cakes are now considered desserts.