Caffeine and theobromine

I've read that chocolate may not even have caffeine in it after all but only similar stimulants, one of which is theobromine. What do you think? Can anyone point to a definitive answer to this?A related question-- I've seen lists of how much caffeine is in dark chocolate. How do they measure that, and doesn't the amount of stimulant vary with the cacao percentage? Surely a 100% bar of 100g has more stimulant than a 55% bar of the same size.
updated by @chocofiles: 05/18/15 05:35:43AM

It depends upon the genetics of the cacao. Some cacaos, such as some Criollo-type populations, have about an equivalent amount of caffeine to their theobromine levels. In fact, it even seems possible for there to be Criollo-type populations with slightly more caffeine than theobromine. Other cacao, such as hybrid and Forastero populations, have far more theobromine. I haven't seen results of any with 0 mg/g of caffeine, but there are some that come close. However, it isn't possible to make a blanket statement that all Forastero has almost 0mg/g of caffeine, because some Forastero populations have more. That is about as definitive an answer as I am aware of.Best,Alan