Question

Some contemporaneous australopithecines have thick tooth enamel, some have thin; some have large canines, some have small; some have large faces, some have smaller. This is an example of __________.

Answer 1

The differences in the tooth enamel, canine size, and facial size among australopithecines represent intraspecific variation, adapted to different diets and environmental pressures between gracile and robust australopithecines.

Step-by-step explanation:

The variation seen in the characteristics of australopithecines, such as differing tooth enamel thickness, canine size, and facial size, is an example of intraspecific variation. The gracile australopithecines, like Australopithecus afarensis, had smaller teeth and jaws, and presented with a more pronounced jaw projection or prognathism without a sagittal crest, while the robust australopithecines like Paranthropus robustus had features like large molars, a sagittal crest for muscle attachment, flared zygomatic arches, and large faces with less prognathism, suited for a diet of hard nuts and seeds.

These characteristics were adapted to different environmental pressures or diets. For instance, Paranthropus robustus had a pronounced sagittal crest which suggests a strong temporalis muscle, important for processing a diet of tough plant materials, while gracile australopithecines like A. afarensis were more adapted for a varied diet including softer foods.