Anatomically humans resemble herbivores much more closely than carnivores. Long intestinal tracts, teeth with flat, non-pointed surfaces, lower hydrochloric acid content in our stomachs, proportionately smaller livers, and the presence of ptylan (an enzyme to break down starch) make our digestive systems ideally suited for a diet composed of fruits, vegetables, grains and nuts, but very poorly suited for a meat-based diet.