The Yerkes spent much of their lives working with primates and studying primate literature. According to Tuttle(4) Yerkes and Yerkes eschewed the "facile" use of the term 'instinct' throughout their book because they had concluded that most apes, particularly infants, will easy accommodate themselves to a wide range of human foods(p. 55). This is presumably the same situation in which we find humans, with no particularly strong instincts to eat particular foods in their natural state. Indeed some of the few drives genuinely found in humans, and therefore perhaps 'instincts', are the sweet tooth, a repulsion to bitter substances and the 'Pica' phenomenon. Humans would certainly not eat the bitter leaves and distasteful fruits that are part of the chimpanzees diet.
An instinctive attraction to the smell of prey species is also not a trait that we find in humans, and would expect of a typical carnivore or omnivore. Fruit eating species locate their foods visually. Archetypical omnivores such as pigs, dogs or bears have acute smell and can locate buried food. Of course, prey can be tracked visually, which is a good method for obtaining some kinds of insects.
According to Chivers(3) humans only make it as omnivores because the application of food processing technologies(p. 4), these allow humans to render tough plant and animal matter edible. He even goes further in stating that omnivorism is impractical because of the inability of any digestive anatomy to deal with significant amounts of tough plant matter, fruit and animal matter. Animals tend to focus on 1 or 2 different food types as the mainstay of their diet.
Without the application of fire and the use of hunting tools, what would ancient human ancestors have ate? Some of paleoanthropology literature suggest that human ancestors were frugivorous, although there is often a suggestion that animal foods were part of the diet, either as scavenged carcasses or as invertebrate matter. Whatever the truth, we do know that modern humans are not attracted to the smell of dead animals. Nor do humans typically hunt down other animals and consume the remains in their bloody raw state, or in the state of decay in which animal foods are sometimes found in the wild when eaten by omnivores. One might suggest that this is due primarily to cultural conditioning, but the facts remain that there are a number of unpleasant risks one faces in eating uncooked animal matter, including various parasites and toxins found in necrotic tissue, and the general unpallettable nature of carrion. Perhaps this is why so much effort is made by humans to disguise the genuine flavour and appearances of animal foods with herbs and other; often plant derived, seasonings a situation not parsimonious with a carnivore or omnivore. In contrast, humans are attracted to the smells of fruits and flowers, and to sweet flavours.