Homo erectus is a key member in the evolutionary history of early humans. Their fossils suggest they lived in Africa and Asia between 1.89 million and 143,000 years ago. Homo erectus is the first species of Homo with modern human-like body proportions, having longer legs, shorter arms, and relatively large brain cases. These features are considered adaptations for living primarily on the ground with the ability to walk and possibly run long distances. This likely led to this species being the first early human species to venture beyond Africa, into Asia. There is fossil evidence that this species cared for old and weak individuals, signaling the appearance of empathy and close social bonds within groups. The appearance of Homo erectus in the fossil record is often associated with the earliest hand axes, the first major innovation in stone tool technology.

Humans are part of a large taxonomic group known as Primates that falls within the phylogenic class that contains all mammals, Mammalia. This group includes our closest living relatives, the great apes, as well as living monkeys, and all extinct early human and non-human primate species. Because we are related, humans and non-human primates share many anatomical and behavioral characteristics. For example, our hands and feet have five digits, we have large brains relative to other mammals, and we have binocular vision in which our eyes face forward on the front of our skulls. Also, some non-human primates can communicate with symbols, occasionally use tools, walk on two legs for short distances, and have complex social interactions. By studying non-human primates, researchers can learn about the ancestry of modern humans and more about the lives of early human ancestors.

By studying human bones, physical and forensic anthropologists can learn a number of things about events of the past and the present, and the people who experienced them. The condition of bones, the location they are found in, and items they are found with can inform researchers about burial practices and the circumstances leading to disposal of the remains. The bones themselves can tell researchers how old a person was, how tall they may have been, if they were a man or a woman, and what role they played in their society. Information on diet and activities in life can be found in bones by looking at their composition. Researchers can also learn about diseases that leave marks in bones and how they affect individuals and populations through time. Bones can sometimes tell researchers how a person died and this information may help law enforcement agencies solve modern forensic cases.