A hominid is defined as ‘modern human and African apes and their direct ancestors. The term previously referred to humans and human ancestors only, under a phonetic taxonomy.’ The earliest well-accepted hominin is the Australopithecus, or Southern ape. Fossils, dated to 4.2 to 2.5 mya have been found in Ethiopia, Kenya, Tanzania, Chad and South Africa. From these fossils, we know that these early humans walked fully upright on two legs, known as bipedalism. These early humans showed prognathism, the jutting forward of the lower face and jaw area, they also had pointed canine teeth like that of apes. They had the brain size of chimps, about 480 ml, and weighed about 105 pounds on average. They also had long and heavily muscled arms and relatively shorter legs. These early hominins looked like apes, except they walked bipedally. Microscopic analyses of their teeth indicate a mixed vegetable diet of fruits and leaves. The fossil skeleton of ‘Lucy’ is an example of Australopithecus. The adaptive themes of bipedalism, large brains, complex social organizations, and tool technology were established during this period. The first hominin feature to evolve was bipedalism, millions of years before the development of our big brains. The evolution of bipedalism with the retention of long, strong, and powerful shoulders and arms was an adaptation to living in an environment of both arboreal (forested) and terrestrial (plains) areas, giving our early ancestors great adaptive flexibility. Bipedalism served various important functions. It freed the forelimbs to carry things such as food or offspring and it aided early hominins’ ability to find food and see danger by elevating the head up. The vertical orientation helped to cool the body by exposing a smaller area to the sun and placing more of the body above ground to catch cooling air currents. Bipedalism was also very efficient and required less energy for long periods of steady walking. Much of what we know about the adaptations and movement of people around the world and their cultural systems is based on our analyses of stone artifacts. The early hominins’ big brains allowed them to better understand and manipulate their environment, making creative technologically advanced stone tools, which helped to provide them with an important new source of food. They used stone tools for sharpening branches for crude spears or sticks for digging up roots, or cutting up plant material for food or other purposes. These stone tools also allowed the early Homos to better exploit scavenged meat and bones from the carcasses of dead animals. The marrow from the bones was a nutritious addition to their diet. Purposefully modified stone tools are concrete evidence of the brain power of early Homos. As well, it seems they lived in small cooperative groups, possibly family units, scavenging the savanna for sources of food. They were vulnerable to larger, stronger predatory animals such as lions, leopards and cheetahs. By hunting in groups they could better protect themselves by having more eyes looking for danger. Most of what we know about the early hominins come from fossil records and artifacts.