Initially, many experts agreed that we didn't learn to tame or control fire until approximately 400,000 years ago. In a documentary about homo erectus entitled "Prehistoric Autopsy," Episode 2 , Dr. Anne Skinner of Williams College in Massachusetts examines scorch marked animal bones dating back to 1.5 million years ago that were found at a site inhabited by homo erectus at the same time. In her research she is able to prove that the temperature used to create these marks was higher than what a natural fire of that environment could produce thus suggesting they might have been created by a man made hearth. In his book, "Adam's Tongue: How Humans Made Language, How Language Made Language  Adam Bickerton also suggests that humans were using fire about this time, listing it among other simultaneous human inventions. Moreover, Bickerton's book dates homo erectus at approximately 2 million years old, examining at great length what was occurring in their evolution at this time. "What's flame got to do with it?," you ask. Well, controlling fire now meant that human ancestors could cook their food, leading to a much better quality, nutrient rich diet over the difficult to digest grains, grasses, nuts and berries that had been relied on prior to meat eating days. Bickerton's theory differs here, preferring what he calls "power scavenging  (involving whatever methods are necessary to claim the prize, in this case, dead carcasses of large animals) as a step up from merely cracking bones with stone implements for the marrow they contained inside. I don't mean to suggest that meat wasn't eaten until our ancestors learned to control fire. Meat, as shown through dentition and gut size in both the video and Bickerton's book (Pp. 157) was a large part of their diet. My aim here is to point out that this discovery allowed them to process the meat more efficiently than the raw scraps they'd previously become accustomed to. More nutrients, easi