Initially humans would eat their meats raw and their stomach's could handle this without getting ill but at some point they started cooking their meat. When did this and happen and why did they do this? Wouldn't it have made them ill? Dogs, as an example, can't eat warm foods because they have never learnt to digest it so how did humans transition from raw to cooked?
This question may be better suited for /r/AskAnthropology
I'd point you towards dishes that are raw in modern days (Steak tartar and mettbroetchen as two examples), being that they're eaten relatively quickly after the animal is killed, cooking the food to kill all the microbes isn't necessary.
Just saying, not dissuading any discussion.