Final answer:
Paranthropus robustus is the hominid species that shows evidence of eating hard objects, supported by specific anatomical features and dental wear patterns.
Step-by-step explanation:
Among Paranthropus and Australopithecus, only Paranthropus robustus shows evidence of eating hard objects. Paranthropus robustus, discovered by Robert Broom, showed adaptations for a diet consisting of hard foods such as nuts and seeds, which is supported by the presence of a sagittal crest and flared zygomatic arch for strong chewing muscles and marked teeth from scanning electron microscopy (SEM) analysis. On the other hand, the Australopithecus species possessed smaller jaws and teeth suited for a diet of softer foods and did not exhibit the same heavy dental wear as Paranthropus, indicating their diet was less reliant on hard objects.