I am not a biologist or anything of that ilk, however I am a bit skeptical that the chimps understood the concept of "cooking" the food. It seems more likely that they understood "hey if I do X, then the food gets more tasty" with X being put the food they have (which is raw) in the "cooking device". Making the leap to saying "yes they totally understand the concept of cooking" seems a bit anthropomorphizing.
To be fair the article added this anthropomorphism. What the scientists found is unlike most animal species, the chimpanzees had enough self-restraint to not eat raw food the moment they found it, if they knew they had the chance to improve it later on.
I speculate that early humans cooked the food for the same reason. How would I prove that, I don't know. But they were not thinking about the nutrient value or killing of bacteria. They probably had a concept of being sickened by food and learned that certain foods will not make you sick if you do this to them first, but initially I think it had to do with taste.
Catching Fire, by Richard Wrangham, is a pretty good read for those interested in the impact and importance of cooking in human evolution. I really enjoyed it.
I'd like to know more about this "cooking device". Was it not really cooking the food, but just switching the raw food for cooked food? What exactly was it?
from the article: "[chimps share with humans...] a preference for cooked food, the ability to understand the transformation of raw food into cooked food, and even the ability to save and transport food over distance for the purposes of cooking."
