Homo sapiens first appear in the fossil record about 200,000 years ago. These early humans were opportunistic omnivores who consumed a variety of foods, including both plants and animals. Prior to this time, ancestral hominid species are thought to have consumed fruit, leaves, bark, insects, root vegetables and meat.
Aside from humans, the other great apes primarily consume vegetation. Chimpanzees hunt and gather some animal-based foods, but these foods generally represent a small fraction of the animals' diets. According to the Nature Education Knowledge Project, early ancestors of humans first began consuming animal flesh and bone marrow at least 2.6 million years ago. Evidence for this dietary shift was discovered in the form of butchery marks present on animal bones. These marks were created by crude rock tools that human ancestors used to cut meat from carcasses.
One of the most significant changes in the human diet occurred approximately 12,000 years ago, when humans began domesticating animals and crops. This allowed humans to produce their own food, which led to the development of permanent settlements.
Paleontologists debate the details of the addition of meat to the human diet. Some claim that humans began hunting before they began scavenging carcasses, while others argue the opposite.