Question

station 3: human and ape cranial and dental differences ape human amount of prognathism canine shearing complex - present or absent canine size - large or small diastema - present or absent sectorial p3 - present or absent shape of chin area/mandibular symphysis- recedes back, vertical, actual chin, simian shelf size of braincase - smaller or larger much vs. little postorbital constriction position of foramen magnum - more anterior vs. more posterior shape of dental arcade - rounded squared, rectangular; are tooth rows parallel? do molars increase or decrease in size from m1 to m3 location of maximum skull breadth (viewed from back) higher vs. lower on skull

Answer 1

Human skulls exhibit less prognathism, absent canine shearing complexes, larger braincases, and a more anterior foramen magnum compared to apes. Human dental arcades are parabolic with smaller canines, and the reduction in bone mass leads to distinct differences like the presence of a chin.

Step-by-step explanation:

The evolutionary differences between human and ape crania and dentition can be observed in multiple anatomical aspects:

• Prognathism is less pronounced in humans, with a more vertical facial profile compared to apes.
• In humans, the canine shearing complex is absent, canine size is smaller, and the diastema (gap for canine teeth) is absent.
• The mandibular symphysis in humans manifests as an actual chin, rather than the receding simian shelf found in apes.
• Braincase size is significantly larger in humans, reflecting a larger brain, especially in the frontal lobes.
• Humans have a reduced postorbital constriction compared to apes.
• The foramen magnum in humans is positioned more anteriorly, which accommodates bipedal posture.
• The human dental arcade is more parabolic (rounded) and the molars do not typically increase in size from m1 to m3.
• Maximum skull breadth tends to be higher on the ape skull compared to the lower positioning on the human skull.

Additionally, the skeletal adaptations reflecting a fully upright and bipedal posture in humans are accompanied by shortened arms relative to the legs and enhanced dexterity of the hands.