Question 6B

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What is thought to be the main reason for the differences in cranial morphology seen between Paranthropus (or robust Australopithecines) and gracile Australopithecines?
 

Paranthropus boisei

Australopithecus africanus

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The sagittal and nuchal crests and the large zygomatic arch seen in the Paranthropus species' indicate the presence of large chewing muscles, and together with the large grinding teeth suggest a diet of tough, fibrous foods.  The gracile Australopithecines do not have the large crests and zygomatic arch, and the teeth are smaller, which suggests a diet of softer foods. 

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