Final answer:
The earliest definite hominids were referred to as Australopithecus. These early human ancestors evolved about 3.9 million years ago and were the first to develop tool-making technology. Other significant early hominins include Ardipithecus and early members of the genus Homo like Homo habilis.
Step-by-step explanation:
The earliest definite hominids, which refer to the line of early humans and their immediate ancestors, were known as the genus Australopithecus. This group evolved about 3.9 million years ago and was characterized by bipedal locomotion and a brain size roughly one-third of that of modern humans. Despite this smaller brain size, Australopithecus species were the first to develop tool-making technology, making them significant in the study of human evolution. Over time, from this genus, various other hominid species evolved, with notable advancements such as increased brain size and more sophisticated tool-making abilities.
Ardipithecus is another early hominin genus that is considered to be one of our earliest ancestors dating to the Pliocene Era, which includes species like A. ramidus and A. kadabba. The earlier genus Homo, which includes species like Homo habilis and potentially Homo gautengensis, emerged later and displayed more human-like characteristics, such as increased brain size and a reduction in the prognathism of the jaw compared to its predecessors.