Final answer:
Early human ancestors exhibited a variety of dentition and cranial capacities, indicative of their evolutionary paths. Homo naledi had small teeth and a brain the size of an orange, while Homo habilis and later Homo erectus showcased an increase in brain volume and changes in dentition aligned with their diets.
Step-by-step explanation:
The dentition of early human ancestors like Homo naledi and other hominids was quite different from modern humans. For instance, Homo naledi possessed small front teeth, alongside a small brain that was no larger than an orange, indicating a separate evolutionary path from other species of Homo with regard to brain development. The species known as Homo habilis, by contrast, had a larger brain volume of about 800 cubic centimetres, which was significantly larger than that of their contemporaneous primate relatives like chimpanzees. The dentition of these early humans often included larger molars as compared to other primate species, a shift likely associated with dietary changes and increased consumption of both plant and animal food.
Further anatomical evolution can be seen in Homo erectus, which displayed more efficient bipedal locomotion similar to modern humans, but still retained larger jaws and teeth and a sloping forehead. As evolution proceeded, cranial capacity increased in some species, such as Homo antecessor which had an estimated cranial capacity of about 1,000 cubic centimetres.
The development of these traits, including small jaws and teeth, bipedalism, dexterity of hands, and increased brain size, particularly in the frontal lobes, was a significant evolutionary step. These changes had profound implications for the ability to create tools, altered dietary practices, and social behavior. However, the correlation between brain size and intelligence is complex, underlined by the differences seen in Neanderthals, who had larger brains but may have had different cognitive abilities compared to modern humans.