i just can say that cooked food has a higher caloric value that raw food, translated that means it is more digestible albeit somewhat less nutritious. that might have had some evolutionary advantages scenarios during hard times when food was scarce. Cooking would kill pathogens thus giving survivors an advantage over those that succumbed to virus,bacteria, or parasites. Cooked meat can be chewed quickly compared to raw although the time required to gather wood and cook the meat would negate the advantage. some foods such as chestnuts(the bread tree) are shelled most easily by fire. lastly, fire side meals were probably a joyous occasion for early man offering some protection against other creatures that feed on humans but fear the fire and smoke. the smell of roasting meat could have helped early man locate other humans for several miles away. bringing new genetic material into the tribe.