Final answer:
P. robustus, a robust australopith, primarily consumed hard nuts and seeds and went extinct more than one million years ago. A. africanus, a gracile australopithecine, had a varied diet and went extinct around 2 million years ago.
Step-by-step explanation:
Paranthropus robustus and Australopithecus africanus were both early hominins with distinctive diets and evolutionary outcomes. P. robustus had a diet primarily based on hard nuts and seeds, which is reflected in its physical morphology, such as a sagittal crest and a flared zygomatic arch designed for strong chewing muscles. Australopithecus africanus had a slender build and a mixed diet, possibly including soft foods, but also exhibiting a trend towards meat-eating as seen in later hominins like Homo ergaster. The robust australopiths, including P. robustus, went extinct more than one million years ago, while the gracile australopithecines such as A. africanus disappeared around 2 million years ago.