Final answer:
Fossils of hominids such as Homo erectus and Homo habilis provide information on ancestors' brain size, bipedalism, and tool use. These physical traits and adaptations like a broader pelvis, round skull, and the ability to make tools are key indicators of early hominin life and the evolution of our genus, Homo.
Step-by-step explanation:
Fossils of hominids that lived in the past provide a wealth of information about our ancestors. They can tell us about how large their brains were, whether they walked upright, and whether they used tools. For instance, the early Homo species, such as Homo erectus, were efficient at bipedal locomotion, similar to modern humans. They had a broader pelvis, longer legs, and arched feet. Despite having bigger jaws and teeth, a sloping forehead, and a smaller brain, these adaptations were critical for walking upright.
Moreover, species like Homo habilis had a brain size of around 661-700 cc, and their hands were capable of the dexterity needed for making tools. This is a significant indication that early hominins used tools. Evidence also indicates that hominins showed signs of reduced prognathism and smaller jaws, which are features suggestive of the genus Homo.
Furthermore, the presence of fully adapted feet for walking and a round, globular skull are additional criteria that were proposed by notable researchers like Mary Leakey, Louis Leakey, and John Napier, for classifying a species under genus Homo. These fossils suggest that our ancestors, such as Australopithecus and H. habilis, displayed early evidence of bipedalism, tool use, and had significant changes in brain size and skull shape that distinguish them from their primate counterparts.