Final answer:
Evidence that the robust australopithecines, particularly the Paranthropus genus, ate hard foods includes their large grinding teeth, the presence of a sagittal crest, flared zygomatic arches for large temporalis muscles, and the wear patterns on their molars as shown by SEM.
Step-by-step explanation:
There are several pieces of evidence that suggest that the robust australopithecines known as Paranthropus were adapted to eat hard foods. These hominins are characterized by their large grinding teeth, heavy wear on molars, and unique skull features. The robust species, such as Paranthropus robustus, had a sagittal crest and flared zygomatic arches that provided a larger surface area for the attachment of the temporalis muscles, which facilitated the processing of tough plant materials. Additional evidence from scanning electron microscopy (SEM) has shown that their teeth had specific wear patterns indicative of a diet that included hard nuts and seeds.
Paranthropus species also had a significant reduction in the sizes of their incisors and canines, leading to a flatter face with less jaw projection. Despite some debate over their diet's variability, this morphological evidence strongly supports the hypothesis of a specialized diet that relied heavily on hard, fibrous plant material, distinguishing them from other hominin species that incorporated more meat consumption, such as Homo ergaster and Homo erectus.