To the best of my knowledge we are the only species on the planet that cooks much of the food it consumes. How did we realize this? Who thought to put meat on a fire? Or that boiling rice made it much easier to eat?
The first evidence of humans using fire to cook food can be traced back to before Homo sapiens to Wonderwerk Cave, South Africa, approximately 1 million years ago, according to a study done by Francesco Berna that you can read here, where the Acheulean occupation of Homo erectus is demonstrated to have manipulated fire to cook animals in a site dated to approximately 1 million years ago. (Side note, I actually helped run some of the FTIR analyses on the bones and burnt sediment, so I know the science is good)
Richard Wrangham in his 2009 book Catching Fire: How Cooking Made Us Human (Basic Books, New York) argues that human anatomy changed to adapt to a primarily cooked diet, and we can see the beginning of this by tracing the changes in our anatomy that we can see in the fossil record, either with the development of Homo erectus at 1.8 million years ago, Homo heidelbergensis at 800,000 years ago, or Homo sapiens at 200,000 years ago. Wrangham traces the inception of fire for cooking to the original change, the development of Homo erectus, which involved larger changes than any subsequent transition (p. 97).
Wrangham notes that in experiments conducted on modern primates the primates unanimously prefer cooked food to raw food. No tested animal preferred raw food to cooked food given the choice. Wrangham uses these experiments to argue that our ancestors would have preferred the taste of cooked food as soon as they were able to control fire, and perhaps it was an impetus in the desire to develop that technology.
Try /r/askanthropology. History really begins with the invention of writing.