candles on cakes

why do we have a cake to celebrate our birthday and why do we put candles on it? i do not believe it is as simple as to represent how old we are, there must be some reason behind this tradition like most other traditions.

I found a couple of sites that look at the origins of birthday traditions and both say the same thing - nobody really knows. Both sites offer a possible origin of ancient Greece, like http://www.fun4birthdays.com/fun/traditions_candles.html where it says:

The world may never know.