Final answer:
The Piltdown Man was once falsely represented with features like a modern human-sized brain and a primitive jaw. True early humans, such as H. habilis, had larger brains and tool-making abilities, while Australopithecines were categorized into robust and gracile based on jaw and tooth size as well as other skull features.
Step-by-step explanation:
Features of Piltdown Man
The Piltdown Man, once considered an early human ancestor, was later proven to be a hoax. However, discussions on early hominin traits often include features such as a large brain, on par with that of Homo sapiens, a primitive-like jaw and teeth, and the proposition that cranial development generally precedes changes in the postcranial skeleton. Among the attributes considered adaptive in early hominins are smaller faces, jaws, and front teeth, complemented by larger brain sizes compared to earlier Homo species, including H. habilis and H. erectus, which displayed a sagittal keel—a ridge on top of the skull. Additionally, other hominins like the Australopithecines, were classified into robust and gracile forms, with the former having large jaws and a sagittal crest, whereas the latter had more humanlike features, such as smaller teeth and less pronounced jaws.
When evaluating a species under the genus Homo, the criteria extend beyond bipedalism and include a brain size over 600 cc, a round skull shape, tool use, reduced prognathism with smaller jaws and maxillae, and humanlike postcranial features including feet fully adapted for walking. For example, H. habilis had both larger brain volumes and the dexterity for making tools, a key distinguisher for classification within the genus Homo.