Final answer:
Early Homo species like Homo erectus and Homo habilis were bipedal, had adaptations for bipedal locomotion such as arched feet, and smaller jaws and teeth indicating a change in diet. Evidence of fire use by H. erectus suggests cooking and meat consumption, leading to changes in dental and jaw structure.
Step-by-step explanation:
Studies of carnivore tooth marks on fossilized bones from the Plio-Pleistocene suggest that early Homo, including Homo erectus and Homo habilis, were bipedal and capable of walking with a human gait. With adaptations such as humanlike feet with arches and ankles, these hominins had a skeletal structure that supported efficient bipedal locomotion. The smaller jaws and teeth, as well as the third molar being larger than the other molars, indicate dietary adaptations. Skull features like a sagittal keel, seen in H. erectus, add to the evidence that while from the neck down they may have resembled modern humans, they also had a different skull shape marked by larger teeth and a sloped forehead, signifying that they were quite different from us cerebrally as well.
Furthermore, archaeological findings, such as those from Zhoukoudian, China, provide evidence of the use of fire by H. erectus around 1.7-2.0 MYA, which is one of the earliest known instances of hominins using fire. This suggests they cooked meat and may have engaged in hunting behaviors, necessitating smaller teeth and jaws over time due to the softer food they ate.